Actor AR Pet SN tetas a EEN RAN A : CEM eae fe va ty ST ga a SA een kA f Stary. gee re 5 ag ¥ wa yates SNS ee Nets ao i i tye lee vee ews Pre # tial : F re a 7 : ieee = Watt ee be eee ‘ PE ge ead setae ‘i year ses F i oe ae re a . , ite a = s eg de a ge yee wary ’ eee het sa ei \ STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION NATURAL HISTORY SURVEY DIVISION STEPHEN A. FORBES, Chief BULLETIN OF THE Illinois State Natural History Survey URBANA, ILLINOIS, U. S. A. Vol. XVII CONTENTS AND INDEX 1927-1928 PRINTED BY THE AUTHORITY OF THE STATE OF ILLINOIS STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION NATURAL HISTORY SURVEY DIVISION STEPHEN A. FORBES, Chief BULLETIN OF THE Illinois State Natural History Survey URBANA, ILLINOIS, U. S. A. VOLUME XVII 1927-1928 PRINTED BY THE AUTHORITY OF THE STATE OF ILLINOIS STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. SHELTON, Director BOARD OF NATURAL RESOURCES AND CONSERVATION A. M. SHELTON, Chairman JoHN W. Atvorp, Engineering CHARLES M. Tuompson, Representing the President of the University of Illinois WILLIAM TRELEASE, Biology Henry C. Cow es, Forestry Epson S. Bastin, Geology WitiiAm A. Noyes, Chemistry THE NATURAL HISTORY SURVEY DIVISION STEPHEN A. ForzBes, Chief H. C. OESTERLING, Editor SPRINGFIELD, ILL. 1929 13455—600 a a e CONTENTS ARTICLE I. EPIDEMIC DISEASES OF GRAIN CROPS IN ILLINOIS 1922-1926. By L. R. Tewon. (102 figures) October, 1927......... 1-96 PBI PARAL UNUSED TN sarap (acta toy ayaa gs Pe ease miei Joi fev are. sea:'a) o\'s-a "al ecejelele ecwedugicece. 0, anwcwiaudvatere 1 Generalimrethodswsed WNT the (SUTVEY 6,55 26 cle ed cme ne cls cere ceiec ee sme 2 PATTIES 1S tm O Lum LU elie vey at dha cNclra ctfatn ofa le teva. eVaie: hers -alie.stis anes te aschaun eud-e/ereteeusyehe ae ates 5 Data on the year-to-year prevalence and destructiveness of cereal dis- ESSAE Eas ote at NRE Ga Meet gata ate al ave) a izist r ae/ era ahs ay avavetarwreie wares erate eratniy 15 Were SES er aicise Seeccla eG atsiacs ho) 4 = oo oie ditie oeverevSiarane Ge See ea cree 18 ESTO AS TTS mc Pen eta iar -Peesraregs os ana ar aCe tae sh a ca atch us voraraiw sai eele eee re. suplenseeem alice 43 SCANMOLMCELE ASPs cryn cian aera ereeve eas Pio\eiSle 6 dares lw cralaerciere ets HS Sa gurete 56 hea Spo and meat StPipe GISCABES. 2.6.56 ciece ec Sle eid ne sede ee eee oe we 61 Summary of all data showing prevalence and destructiveness....... 71 Some relations of disease to weather and climate.................... 79 Relation to mean annual temperature and total annual rainfall..... 80 Relation to seasonal temperature and rainfall..............-...... 83 Geographical occurrence of dates of first spring infection, and the temperature relations governing the subsequent development of ELINOR OTOL GEYELCiten state Secreta aiccret ms eR tas suateleracbscsvachots sales seetacaisso) acts assseereue 90 RS LTH CUP VAI ae COM CUIISLON wiateresie cic aieisrelelats.f eicisie iron ieremicion cere oie cele nel stern ooo velte iter pais ete ae Renee 194 CONTENTS y ARTICLE III. AN EPIDEMIC OF LEECHES ON FISHES IN ROCK RIVER. By Davin H. THompson. November, 1927................ 195-201 PATNI CANI CS AULSES YA Oames eta e PoE ey ont ess Soret seencs ake esalicy evclanaive av a dvawatGnore crane Naneencrae seeks 195 BYR GOME nO Lue GH Cj CDE GILL G wis ta ayer oy oy ctat/an sites ot-otc) oars) o)e ave! syst aves" srore cole oi wseitonssehere 195 SCASOM Al ADITS! 10S) sU NG MLGCCHES ao svete to oi v1 avenerercl aiersieie/> leyeveisreietohelova er eveleters 196 MOD SAC VOUT SU COT Meany Reever etree tents rete oy eretis chat wot pre sce ora: 6,0 sustio, w wiclci ainda vere: oneesueeiethele wie 199 CO OMT CULE CLI CM Wee tealenetentecetsor ce psnehed ataisvae cscs ro. tr aloo to rane. civerter ay SvcofieverevevenSuetlovihnttnsonctie 199 BV VMEOTESD OCICS sO MUSCLE OLD cere cee shee: eie cris. eva) bie: oe Siete, ee eoeteveicvslsha a: crela;everess 200 EC ROTM Haeyal CL Cl srsastenct rey search chclehav cts ora Sicrelelenelevetevel co ie lac vevennerelel ovetanotewes 201 Morea ALU CH OVI OLE ART SUNE CMM fateh ne cee pate ee ess airarert foensye.evetroinere, » Sie veliard widhe!nue uvetibunver Gisyanele tere re 201 ARTICLE IV. THE PLANKTON OF LAKE MICHIGAN. By Samuver EDD ome VLE DOL a pL ele eisteicliel erste sis vies ace els avs so is ecyueustaveters suicides 203-232 TUONO CLC LLG ime rey sede et tessr ten evarratetene sit sich sicieliaceta aivts ipictle avers) avasanegale join erevsintereveecare 203 WES PLEO ea cual OPTI AU CLLOUL Store eye tame tist ei, arc. ee cereveneieifaicvsi'e {hive loivel'sa'euc oye vei orelle\cleliece 203 HAO STCH COM CEULONS) weve tarcie wievevererelafoyne is eleusver.e: ato, aralrola rade sahelerahecavoveianevapeusvers 204 Generale CHaAnaACher waitin: cree eicye tee rats) ste chevarss si tere alesse creed eral tyeciy Gidavacere s 205 SS COS OM MASE C Uimarelcteiercteretcuetaisis ot oneLess ops, stay cuaitnate. clay Gael syetslebebe reve) ee ea 256 Appendix— A. ; Definitions. of LENS eh re-ciscer eels oucsekete cosls: oh ieiaenehouse siela) =e 258 B: Bixperimental - methods. ion sce. 2b ciciw soehese: one, sv ig os, eile: crenata 259 C. Analysis of tap water used in experiments................... 259 ARTICLE VI. SOME CAUSES OF CAT-FACING IN PEACHES. By B. A. Porter, S. C. CHANDLER, and R. F. Sazama. (10 figures) March, 19 28° suas s.azepchooneectatelecince das atte apace tesic. sO levslahe Sane 261-275 Tmtrodmetion: |). vcarsie. syotevslalle state earn eioitaveise crime ticks sue +a) Saath ete ea eee 261 Nature Of; the: TG Uy ricicite sale dne eepate Picea ree cemarsteier cus ene .edererorawene cornea et een 261 TOSSES) | oiscau cede, he yees eke PR penn Ete et eee es Sate ne) IIE slo ates 6 ee er 262 IPEOCEGUTE! Aye ci2-5 ones eevee payee rene eushe aetna e oie cease lel vacua preteve elolar's = to 262 Some insects that) cause ‘cat-facime 33 cc cece ku wisje' oo cere 5 oyeje) sheen 264 The: tarnished plant, MoWeiecers ccaeverte sce sy. cle rsl ade oye. v's, =t'0, oo) oe) nee eee eee 264 S CUT Ks Wiese Sas ss Sie: cee cege teeret eset ema peneeteme ee cote Vaseas 10's cas soto <0) oe 268 The plum curculios 5... ei stectslcueteeterel ole eeeicve sic lo. sasie iors 6 =40) sl > Gone he eRe ae 269 Other possible’ CAUSES... 6.05 /ykwis iw retyewe eyes ois, el woes sun love ate: 0 fakes) Usenet Ee 269 Relative importance of the different insectS...............00eeeeeeee 270 FLOst' plant PelatiOrnis Avcerens love: ore sietsyecedcieteie seeteyaie le vic rove (ela? ace; oheve, ohe hone ee eee 271 Hibernation of the tarnished plant bug............-. 2... eee eee eee 271 Control of the tarnished plant bug and the stink bugs.............. 272 Insecticidal! controll. c2iw-)s seis t writs, < sess ews elvisis cee euels.e eee ere 272 CASE» ESE. syalern van tecennrenere ceepaimennencee tayatatog statin) sat erate ietage’/inu creltah eh 3) eee 272 Controleine the Onen arg y, ns strs cies e Sra yansis nets We icr, a2 oe eee 273 Repellents 1g, Berek o iene seek eerste teete, ete Meas sees tee 273 Control of the cumewliOi 5 aes wer secs coo veteee sos, cue ace sleeve the buss oe beds Mea 274 Who ob bb atten ine tar Leas anh Rae Onno es CREE IO Eee E oo oo 2 274 SUMMIT yess cer cts even sie tence hela ere ceiver tye marcberntars waste nenaesoreiereabis re isis Gleeson enema 275 ARTICLE VII. THE BIOLOGICAL SURVEY OF A RIVER SYSTEM— ITS OBJECTS, METHODS, AND RESULTS. By SrEepHen A. FORBES: “March 1928" eictiete ce = aeejewiepe scent Steusis wcernelae cepa ecain f ae eee 277-284 ARTICLE VIII. THE “KNOTHEAD” CARP OF THE ILLINOIS RIVER. By Davin H. THompson. (14 figures) October, 1928..... 285-320 FOG WOT |S iaea rete ores apee ere ectiseaavel re ese e carers Heme ie salle ene Sie bee e len ateh ies eee 285 Introduce css). Rake ahels o npatotserter crete ee tetelie ie ca chisy eave fot elie uel iene sea eee ms 285 Description! ofs KnOGHEAG MCAT Piste cttece steve eye olen tal oy ayer enelotar= easter pete er eee 288 Distribution Of KnOtheadi Campa este ceil tere eres aralaedetc ieee ne eal nen 300 Relation: ‘to: poll wtlom erect crs aoe tiers otctare stone nate aya leeler-y= cnc erate beaten eeeatente 301 Changes in the food supply of the Carp......... eee eee cece cence eee 804 Rate of erowthy Of eMOtWead sity srvetegerese-talet-telsieyiees)ataiol-0-etaleby tered Meena 306 CONTENTS vii BEN AVLOTNOLAI MO URECAGH CAD isus\eterafelarslozsrajers\ crete foie ciate oe corovete Gs vee raccye.gle avaneed 313 Epolopy. of Knothead GiISease’s 3020006 scice sac whic ees incase deweccoee 316 FOCI GIITS LO Dimmrer eter at oneyayretstt ose che lene cto da'as oie reliecs a tate lore isi eee, pe) audio) av exakolne mite amar Mees 320 ARTICLE IX. METHODS AND PRINCIPLES FOR INTERPRETING THE PHENOLOGY OF CROP PESTS. By L. R. Trnon. (18 fig- ures) July, 1928 «SRE arinlind BOD BAG OD TEIO ICIS POIRIER RATE oR eee 321-346 PeniTpANC CALL? trl OT east Rey etePetoN sedated he fe teiaoletals is) ave, le (oyors,uisa¥etayevane eterenstensssvenetsbetahroettene 321 Graphic depiction of climate and weather...............-...0eeeeees 322 Weather in relation to the late blight of potatoes.................... 323 Thermobhyetics of the beet leafhopper and sugarbeet “curlytop”...... 327 Thermohyetics of the cucumber beetles and the bacterial wilt of melons 331 PIPMINCANCE, (OLM AV EMCEE AIS wienctncs sista glare svevaiere aie cise 3.uhe w.ninc.eievece saeenes 339 SPELT ALY eaten state Syeral sto ater eis i skersinh vlaie et eucle a¥e nee week sianaiie,e Ju, savelocé"Sratel ates aca 346 ARTICLE X. AN ACCOUNT OF CHANGES IN THE EARTHWORM FAUNA OF ILLINOIS AND A DESCRIPTION OF ONE NEW SeHOumS. By MRANWK Snr August, 1928.0.0 sce cs vecnsceea ce 347-362 RENIN OCIUILC U1 CT Mrratevey cy eucte scheme ci suctenetcits et si eit s/o lover ev'ey cera atmanacal'arcateyoreishepseaces:avecs Sete 347 AIEEE IE SUN TM ED CLE Hime fee rey ceMeral tie gel aa iar we AUS Toi Gig, Grass, Sie! oleh ta acdeie cal avalarse. ecard’ eave cee 348 WD O MUU SOG CLES MMR ay percicta petal ciatetnietey eyo) s)eenel eles cistesp-lcriare: oreefsusatevets. ays efessrelers 349 SE EOL IECLESSI Eo toaataitiatabenes Tariana cata Gino. sowie eaerm Wis, vee #0 esl weeelte:mcigvab eee 349 Additions: to) the list of Dlimois eCarthworms........ 2.5.22. ees ences 353 MISIOM MS EMO ELT ITE GSTS a peas ace eter ele ecg ce S689 wn lasaveraie ares we 8 ears 353 FEST Tt eh Uae ea Te cl CUCTIS Mens h austen yatta fats, ella) eleh'cn' the value of which, 5.3664 per cent, represents the average amount of disease for every plant in the field in question. As it is customary to record data secured in routine field examina- tions as percentages, a convenient short-cut may be taken, in which the percentages are treated as decimals—.208 x .258 in our example. Per- céntages being expressions of parts per hundred, the use of the decimal point automatically eliminates the denominator of the fraction given in the preceding paragraph, and the result—.053664—appears at once as the product of the two decimals. This product may be expressed as a percentage by moving the decimal two places to the right. By the methods now outlined, the following data have been secured from the field represented by the record blank shown on page 4. 1. 20 acres of wheat. 2. 25.8 per cent of the stems bearing disease. 3. 20.8 per cent of the leaf area on these culms destroyed by dis- ease. 4. 5.36 per cent of the leaf area infected, on an average, for every stem in the field. These items are recorded for every field examined, as many fields of each crop being visited each season as circumstances will permit. In bringing together the data for each disease, the field record sheets, assort- ed by diseases, are arranged in their folders first by counties (the counties, for convenience, following one another in the alphabetic sequence of their names), and then in the order of dates of examination. Finally, they are given numbers which are placed at the upper right-hand corner and serve the same purpose as the numbering of the pages of a book. DISEASES OF GRAIN Crops, 1922-1926 S, The data presented by the sheets in each folder are then arranged in a table, in the manner illustrated by the following short tabulation. TABLE I AN EXAMPLE OF THE First TABULATION AND CALCULATION MADE WITH THE DaTA PRESENTED BY THE FIELD RECORD SHEETS The data used relate to wheat leaf rust Prevalence: Stems with diseased leaves Destructiveness: Leaf- area diseased Record Acres Acre- Acre- See County ex- _Per- age- Weight-| Per | age- Weight- . amined centage per- ed per- |centage per- ed per- ob- centage centage ob- centage centage served | product served | product 1 2 3 | ea | srr | 6 wma 8 9 1 | Adams 20 | 25.8 516 20.8 10,732 (5.3) 2 Adams 12 160.0 1,200 40.0 48,000 (40.0) 3 Adams 20 90.0 | 1,800 | 65.0 | 117,000 | (58.5) | ——_—__| | Total 52 3,516 67.6 | 33.7 | | i | | 37 | Tazewell | 40 100.0 | 4,000 | 55.0 220,000 | (355.0) 38 Tazewell | 20 90.0 1,800 60.0 | 108,000 (54.0) 39 Tazewell 20 90.0 | 1,800 | 30.0 | 54,000 | (27.0) 40 Tazewell / 2 } 60.0 1,200 | 20.0 24,000 | (12.0) Total | 100 | |} 8,800} 88.0 | | 406,000 | 40.6 } | | / | | | 42 Will 1] 100.0 | 100 | } 7.0 | 700 | (7.0) 43 Will 40 | 90.0 | 3,600 | 15.0 } 54,000 | (13.5) | | =e — Total 41 | 3700 90.2 | | 54,700 | pee | | | | | | | | | Total | 193 | } 16,016 82.9 636,432 | 32.9 | | The first column contains the page numbers of the record sheets, which serve as a means of referring the figures in the table to the sheets from which they are taken. In the second column appear the names of the counties in which the observations were made, and in the third column are the acreages of the fields examined. The fourth, fifth, and sixth columns are concerned with data bear- ing on the proportion of disease-bearing plants. In column 4 appear the observed percentages shown by the record blanks; and; in order that the necessary calculations may be made, column 5 contains the products se- cured by multiplying the acreage of each field by the percentage of diseased plants found in it. For want of a better term, this quantity is called the “acreage-percentage product.” Since the individual percentages entered in column 4 usually apply to fields of different sizes, computing this pro- duct gives a proper acreage weight to each observation. The process of weighting in terms of acreage is exactly similar to that explained al- ready (see pp. 6 and 7), the construction of the table permitting, however, the use of the short-cut described therewith. The sixth column contains the percentages indicated by the weight- ing process as the proper averages for the county groups of data on prev- alence and, finally, the weighted average for all these data. 10 ILitinois NAturAL History Survey BULLETIN The last three columns show the amount of disease per plant. The percentages of disease observed in the individual fields are entered in column 7 directly from the record blanks. The process of “weighting” to secure the true average percentage for all the observations requires that the product of the items of columns 3, 4, and 7 shall be obtained in each instance. When secured, it is listed in column 8. From it, a percent- age, listed in column 9, is obtained for each observation by dividing by the acreage. In the table above, this final figure for each field is shown in parentheses because it is not used in computing the final results. In prac- tice, it is neither computed nor written into the table. The weighting accomplished in column 8 permits direct computation of average percent- ages of diseased leaf-area for each county and for all the data. These important items appear in bold-face type, in the last column, and in prac- tice they are the only figures entered there. This table, which is made up entirely from the data secured in the field, is designed to show: 1. Prevalence of disease, by counties, in terms of diseased stems. 2. Severity of disease attack, by counties, in terms of plant parts occupied, or killed, by the disease-producing organism. 3. Prevalence and severity for the total acreage examined. To distinguish between prevalence and severity is not only logical but necessary. It is comparable to the distinction made between the prev- alence and the mortality-rate of human diseases. The prevalence of diphtheria, for example, is expressed as the proportion of the population contracting the disease, but the mortality—the deaths—due to it, being much less than the former, is a separate consideration. The proportion of plants becoming infected is, quite comparably, a measure of the prev- alence of plant disease, and the amount of plant tissue occupied or killed is likewise a proper measure of what may be termed “plant mortality.” Hence, the figures which conclude the above table may be interpreted as meaning that the disease to which they refer was 82.9 per cent prev- alent and resulted in a “mortality’—destruction—of 32.9 per cent of leaf, in the acreage examined. The term prevalence is quite appropriate; but the fact that few diseases bring about either immediate death or complete destruction of the plants they attack makes it desirable to replace “mortality” with a more suitable word. The attacks of cereal diseases are limited, in the main, to specific plant parts, either actually, as are leaf spots and rusts, or in their outstanding effects, as are smuts. The damage they do is cor- respondingly limited, consisting of a measurable destruction of particular parts. For this reason, “destructiveness”, applied to the parts of an individual plant, is a better expression of the severity of attack. The weighted prevalence and destructiveness percentages determined in the foregoing table and in two others described on subsequent pages, besides being precise analytical summaries of data, may be regarded also as arbitrary indexes. Complete prevalence or destructiveness would have an index of 100, while lesser degrees of prevalence or destructiveness would have indexes proportionately less—82.9 and 32.9 in the example. DISEASES OF GRAIN Crops, 1922-1926 ae! Because the quantity of data pertaining to any disease that is secured in a season is limited by the amount of help available, the duration of the period of prevalence, and the opportunities for examining the crop it infects, that which is obtained is regarded as exemplifying the disease condition existing not only in the fields that were seen but also in the territory adjacent to them, and in the State as a whole. It is, therefore, necessary to transform the field data, by more extensive calculations, into terms representative of these larger areas. Statistics relating to acreages and yields of crops in Illinois are fur- nished in the reports of the Agricultural Statistician*, in which the counties, used as statistical units, are grouped into the nine geographic districts shown in Figure 1. Acreages and yields are given not only for Fig. 1. Tue pdIsTRicts INTO WHICH ILLINOIS IS DIVIDED IN COMPILING AGRICULTURAL STATISTICS The counties of Illinois are divided by the Agricultural Statistician into these 9 nearly-equal groups. The same grouping is utilized conveniently in the analyzing of plant disease data in connection with agricultural statistics. the entire State but for the counties and districts as well. Because the observations on diseases of cereals are made on an acreage basis, the sta- tistical units adopted for crops are conveniently utilized in the further analysis suggested above. Adjacent territory is defined, for statistical convenience, as the acreage devoted to a particular crop in the county in which disease prev- 2 * Illinois crop and livestock statistics. Issued by the U. S. Dept. Agr., Bureau of Agricultural Economics cooperating with Illinois Dept. Agr. 12 Intinoris NaturAL History Survey BULLETIN alence and destructiveness have been measured in sample fields. The weighted percentages, expressive of prevalence and destructiveness, that were obtained for county groups of data in the foregoing table are held to represent the prevalence and destructiveness of disease in the entire acreage devoted to the diseased crop by those counties. Proceeding on these assumptions, the county acreages reported in the agricultural statis- tics and the disease indexes for the counties shown in the first table are combined in a second tabular computation, in the following manner. TABLE II AN EXAMPLE OF THE SECOND TABULATION AND CALCULATION Mabe witH Disease DATA The county acreages for a given crop, as estimated by the Agricultural Statistician, are combined with the county indexes of prevalence and destruc- tiveness computed in the first tabulation, and indexes obtained from them for the total acreage directly represented by the sample fields. These data apply to the leaf rust of wheat. | pee, | Prevalence: Stems |Destructiveness: Leaf- r ~ | with diseased leaves area diseased |} Wheat a sist County | Senne | Weighted Acreage- Weighted Acreage- | county | percent- j|percentage percent- percentage | ages per product ages per product eounty per county county per county il 2 3 I B) 6 INGE MAS), | Of clasa aes Brig, cecio e< 61,400 90.0 5,526,000 40.4 2,480,560 (Gee aha A aeons SAS 29,600 100.0 2,960,000 15.0 444,000 ise weblion Sona Ss Oo 5 24,500 22.8 558,600 ene 188,650 IMWOE CRW mee cls Gd oer tio oo 42,300 93.7 3,963,510 39.8 1,683,540 SVVALLEG Peucgesesanensesstistataiemeite 59,300 97.4 5,775,820 38.6 2,288,980 Totals for the coun- | ties listed ........ 217,100 86.6 | 18,783,930 | 32.6 7,085,730 In column 1, all the counties are listed which appeared in the first tabulation. Their acreages of the crop concerned, taken from the Agri- cultural Statistician’s reports, are listed in the second column. In columns 3 and 5 appear the weighted percentages of prevalence and destructive- ness, respectively, which were computed for each county in the first table. As the acreage devoted to a given crop in one county is seldom the same as in another, it is necessary to give the percentages of each county weights which are proportionate to their acreages. Weighting is done here in the same manner as in the first tabulation, except that, since a true percentage of destructiveness is used in column 5, the acreage-per- centage product in column 6 is obtained directly as the product of the items in columns 2 and 5. When all the items needed for the tabulation have been set down or computed, the figures in columns 2, 4, and 6 are added, and the totals of columns 4 and 6 are each divided by the total of column 2. More DISEASES OF GRAIN Crops, 1922-1926 13 specifically, the sums of the acreage-percentage products for prevalence and destructiveness each are divided by the total acreage of the crop in the counties listed. The resulting quotients—86.6 and 32.6 in the ex- ample—are weighted percentages indicative of the prevalence and de- structiveness, respectively, of the disease in question in the entire ter- ritory adjacent to the fields from which data were obtained by examina- tion. In order to compare prevalence and destructiveness of diseases year by year for the entire State or for smaller districts, it is necessary to go a step further and compute indexes which will apply to the State’s total acreage of a given crop in each year, and to the acreages of the sta- tistical districts (see page 11). Satisfactory indexes can be obtained for this purpose by extending the observed data, first to the county acreages, as was done in the foregoing table, and then to the total acreages of the agricultural districts and of the State. An example of the method is given in the following table. TABLE IIT AN EXAMPLE OF THE TABULATION AND CALCULATION USED TO OBTAIN INDEXES OF PREVALENCE AND DESTRUCTIVENESS FOR EACH OF THE Nine Districts AND FOR THE ENTIRE STATE These data apply to the leaf rust of wheat. For the sake of brevity, it is assumed in this erample that the State is composed of the three districts listed. | Acreage-percent- Weighted | Acreage-percent- age products by percentages Wheat | age products by . Wheat counties by districts ra distriets ounties acre- | = eee grouped by age aoe districts per De- Mee county| Preva- Destruc-) Preva-' struc- | aot Preva- | Destruc- lence j|tiveness| lence tive- | lence | tiveness | ness | a eee 3 } et 6 Taal s 9 Dist. 2 | Cook 3,200 10,560 512 | La Salle 41,300] 4,130,000) $26,000 | |. | { | i} | Total 44,500) 4,140,560 826,512} 93.0] 18 .5/146,000/13,578,000| 2,701,000 Dist. 3 | | Adams 61,400] 5,526,000!2,480,560) | Hancock 57,300] 5,512,26011,358,010 MeDonough 44,000] 4,400,000) 880,000 Total 162,700/15,438,260|4,718,570 94.8 29.0/348,000/32,516,400| 9,947,000 Dist..7 | Coles 22,100 360,230 50,830 Douglas 21,600) 1,944,000! 388,800! | Fayette 44,100] 4,410,000) 934,920 Marion 14,600) 1,460,000) 511,000 Shelby 40,800) 3,170,160 428,400) Total 143,200|11,344,390 2,313,950 19).2 16.1/303,000/28,997,600) 4,878,300 u | | SHEN EE) OGCO IEA NE 8 Bor bn) ne woe ee) (ee RC EN 88.5] 22.1/792,000|70,092,000)17,526,300 14 Intinois NAturAL History Survey BULLETIN With the exception of the district acreages shown in column 7, which must be secured from the reports on agricultural statistics, this table is made up entirely from Table II. First, the counties appearing in the two previous tables are arranged in proper district groups in accordance with the districting in the statistical reports (see page 11). They then are listed in column 1. In columns 2, 3, and 4, the acreage of the crop per county and the acreage-per- centage products relating both to prevalence and destructiveness are en- tered, the figures being transferred directly from Table II. Totals are taken of the items in these columns for each district, and the weighted district percentages shown in columns 5 and 6 are obtained by dividing the two sums of the acreage-percentage products by the total county acreage. The resulting quotients represent prevalence and destructive- ness by districts. In column 7 are the acreages reported by the Agricultural Statis- tician to be devoted to the crop in question in each of the districts. The acreage-percentage products in columns 8 and 9 are based on these dis- trict acreages. They are obtained by multiplying the district acreages by the corresponding weighted percentages entered in columns 5 and 6. When all of these items are entered, totals are taken for columns 7, 8, and 9. The totals of columns 8 and 9 are divided by the total of column 7, which is the State acreage of the diseased crop. The quotients thus obtained are placed, for convenience, at the foot of columns 5 and 6. These final weighted percentages—88.5 and 22.1 in the example—are concise expressions of the average prevalence and average destructiveness of a disease throughout the State. It probably has been noticed that in the sample tables no calcula- tions have been carried farther than one decimal place. Because most of the computations involve percentages, which are arithmetically really decimals extended to the second place, the usual mathematical procedure would be to stop the calculations with the first decimal and then either increase the unit place by one or discard the decimal, as it was either greater than 0.5 or less than 0.6. However, as round numbers occur very often in the acreage statistics, it is possible to retain the decimal with- out adding greatly to the labor. The result is that the final percentages, though not greatly influenced, are a trifle more accurate than they other- wise would be. In practice, computations similar in all respects to those just de- scribed are made whenever possible for every disease for which field data are secured, and each year’s folder of field records for each disease contains these statistical analyses, comprised of the three complete tables, as a part of the permanent record. DISEASES OF GRAIN Crops, 1922-1926 15 DATA ON THE YEAR-TO-YEAR PREVALENCE AND DESTRUCTIVENESS OF CEREAL DISEASES In order to obtain useful data on disease prevalence, fields must be examined in as many parts of the State as possible. Traveling by auto- mobile, observers go from county to county, visiting fields along the way. This amounts in practice to a random sampling of disease conditions in crops throughout the State, the quantity of samples taken of each disease on each crop depending on the intensity of cultivation accorded it, the number of observers at work, and the length of time elapsing between the appearance of a disease and the arrival of harvest. The procuring of the data presented in this paper has been influenced also by the fact that the observers at the same time were gathering similar information on diseases of the tree and bush fruits and forage and truck crops. Through the summer of 1922, four men acted as observers; in the summers of 1923, 1924, and 1926, two men; and for the greater part of the summer of 1925, only one man. This, to- gether with the large size of the State, the number of crops to be examined, and the number of diseases—more than 200 of which are serious—to be seen, contributed to what may appear an unnecessarily haphazard grouping of the grain fields subjected to examination. But the wide prevalence of diseases and the comparative uniformity of their destructiveness in regions having the same latitude compensate in a large measure for these apparent but unavoidable faults. Cereal crops are grown throughout the State, some intensively in all parts, others only in restricted regions. The acreages devoted to par- ticular kinds vary considerably in different regions, as shown by Figure 2 which presents graphically the acreage statistics reported for 1925 by the Agricultural Statistician. The lines in this figure which divide the State into four roughly equal parts follow county boundaries, separating the counties into groups characterized in the main by the intensity with which certain cereals are cultivated. Corn predominates in each of the four sections, with a total of 9,240,000 acres in the State, or almost 56 per cent of the total acreage for all grain crops. Oats rank next to corn except in the south where the oat acreage is exceeded by the wheat acreage. Wheat has large acreages everywhere, although it is exceeded by barley in the north. Barley is important only in the north, and rye is unimportant when compared with the others. In the two central sections, which together have 62 per cent of the State’s grain acreage, the order of importance of the various crops is: (1) corn, (2) oats, (3) wheat, (4) rye, and (5) barley. In the northern section, the order of importance of crop acreages is: (1) corn, (2) oats, (3) barley, (4) wheat, and (5) rye. 16 Ittinoris NATuRAL History Survey BULLETIN Corr) 2,337,000 Oats 4,49G000 Wheat 2/8500 Frye S35,500 Barley 259500 Corv? 3,558,000 Oats ZO 54000 Wheat 728200 Frye / 8800 Barley 73000 Core? 2,595,000 OAS 3876000 WAeat 688200 Frye 73500 B orvey F250 Carr? 1,0 02,000 OATS 304000 VA0cat 5I6,/ 04 OPE 4200 , Barley ZR 5@ Fic. 2.. ACREAGES DEVOTED TO THE GROWING OF CEREALS IN DIFFERENT SECTIONS OF IntINors (1925) Next to corn, which is the most important crop throughout the State, oats have the largest acreages in all sections except the south where wheat is grown more extensively than oats. Wheat is a major crop in all sections except the north where its acreage is slightly smaller than the barley acreage. Rye, though important in the north, is almost negligible when compared with the other cereals. DISEASES OF GRAIN Crops, 1922-1926 17 A slightly different order prevails in the south, where wheat is second only to corn, with an acreage almost twice as great as the oats acreage. Rye and barley, both unimportant, are fourth and fifth, as in the two cen- tral sections. The data secured in sample fields representing these acreages and analyzed in accordance with the simple methods described in the pre- ceding pages will serve as bases for comparing both the prevalence and the destructiveness of diseases during the period covered by the sur- vey—1922-1926. For brevity of treatment, it is advisable to group cereal diseases into general classes according to the kinds of imjury they cause, thus bringing together those reqwring similar handing both in securing and in analyzing data, in order to eliminate constant repetition of method and description. If descriptions of individual diseases more complete than those given here are desired, they may be found in the report referred to at the beginning of this paper. Cereals are grown in fields comprising, as a rule, rather large acreages. The plants are small and grow closely crowded together. These two facts have an important bearing on the obtaining of disease data, for even in a very small field an examination of every plant is an impossibility and, furthermore, the crowding of plants makes it extremely difficult to distinguish one from another without digging out and care- fully separating them—a procedure which would not, and should not, be tolerated by the owner of a field. Hence, it is necessary, in securing data representing prevalence, to use the stem instead of the plant as a unit. The degree of prevalence is indicated by the proportion of disease-bearing stems. Counts are made of a number of stems sufficiently large to give a dependable representa- tion of the infection in the field. Because of variations in soil and topography, disease prevalence is apt to vary noticeably from one part of the field to another. In order to equalize such variations, parts of the field count are apportioned to different places. The selection of the places for the counts and the decision as to the comparative number of stems to be counted in each place rests upon the judgment of the observer, but his aim must be to secure as true a representation as possible. Inasmuch as each disease destroys a particular part of its host, the measure of destructiveness must be suited to that part. The device used is described in the discussion of each disease. It should be explained at this point, however, that although neither the devices for measuring destructiveness nor the methods of comput- ing values from the data obtained by using them were employed ex- tensively or consistently in the first years of the survey, the collection and preservation of adequate and representative samples enabled us to measure, at a later time, the destructiveness of diseases during those years. 18 Ittinois Natura, History Survey BULLETIN CEREAL RUSTS The most constantly prevalent type of disease in our grain fields is that known as rust. No cereal crop grown in Illinois escapes at- tack, and with the exception of corn, each is subject to two distinct rust diseases. The rusts are almost unique, in that they are not amenable, under present agricultural practices, to treatments designed either to prevent their attack or reduce their destructiveness. They present, there- fore, the outstanding opportunity for a study of the relation of disease to the na‘ural environment. Rusts do not kill their hosts. Individual infections are limited to very small portions of the plant, seldom extending over an area twice that of the rusty pustule which is the outward sign of the disease; but a multiplicity of individual infections results in the conversion of a large part of the host tissue to the uses of the parasite, giving the appearance of a heavily rusted plant. Measuring the destructiveness of a rust attack thus becomes a matter of ascertaining the relative abundance per plant of the individual infections,,or—for convenience—the relative amount of plant surface occupied by pustules. An actual measure- ment of this area would be impracticable, of course, under field condi- tions, and a substitute must be used. A standard was devised by N. A. Cobb in 1892, which he used extensively and successfully while studying rust diseases of grains in Australia. An adaptation of it which has been used extensively in ex- perimental work has been found equally useful for field work. As in- dicated in Figure 3, it consists of a number of diagrammatic pictures 65% 100% Fig. 3. SCALE USED IN MEASURING THE INTENSITY OF RUST ATTACKS Because the diagram at the right represents the highest possible degree of infection, it is assigned an arbitrary value of 100 per cent., and the gradations represented by the other diagrams are in the indicated proportions with respect to it. Specimens of rust, selected at random in a field, are compared with the standards in this scale, and an average of the readings so secured represents the infection in the field. (See page 19.) DISEASES OF GRAIN Crops, 1922-1926 19 which illustrate a series of typical rust attacks ranging from slight to heavy by easily distinguishable intervals. The classification of the units in the series is based on the relative abundance of rust pustules. The heaviest attack illustrated is the heaviest infection possible and is given an arbitrary value of 100 per cent, the lesser infections being graded as percentages in their proper relation to the heaviest. A copy of this scale is carried by the observer in a small notebook. As he makes his counts in a field to determine the number of stems carrying rust, he selects from time to time and quite at random a copious sample of the disease, which, either then or later, is compared with the scale by fitting its individual parts, one after another, between the two diagrams which they most closely resemble. In order to elim- inate errors of judgment as completely as possible, each part of the sample is classed as the lesser of the two units of the standard between which it falls, rather than being assigned an estimated intermediate value. From one sample so measured (see the typical record sheet on page +), the following data were secured. Scale classes of Number of parts of the Class value rust abundance sample in each class_ times frequency 0 per cent 3 0 ines = 19 95 10 Z 37 370 eo pes 26 650 40 14 560 65 7 455 100 1 100 107 2,230 Destructiveness (mean og 3 sample) of rust on disease-bearing stems, ; = 20.8 per cent. These items are recorded on the field record sheet, and serve as a complete and permanent record of the examination made in that field. Since the individual values given above have no adaptability as a usable figure, they must be reduced to a single value representative of the whole sample. The simplest way to obtain it is to compute the arithmetical mean. This process will require some explanation. Since it is obvious that the larger numbers of moderately rusted sample parts will have a greater significance than the lesser number of heavily and lightly rusted parts in determining the average of the sample, it is necessary to give each class of infection its proper weight with respect to the other classes, as determined by the number of parts of the sample falling in it, by multiplying the value of the rust-class by the frequency with which it occurred in the sample. The product in each instance, in- dicated in the above tabulation as “class value times frequency,” shows approximately the total rust infection in that class, and the sum of these products is approximately the total rust infection in the sample. To find the average rustiness of the sample, it is now necessary only to divide the sum of the products of the class values and frequencies by the number of parts in the sample. The value resulting, 20.8 per 20 Ittino1is NATURAL History Survey BULLETIN cent in the above example, is considered to represent the destructive- ness of the rust on the disease-bearing stems. For the field as a whole, destructiveness is calculated by the methods outlined previously (p. 8). In the main, the rusts of cereal crops are classified as “stem” rusts and “leaf” rusts, according to the plant part which they customarily inhabit. This characteristic demands that the destructiveness of stem rusts be measured as diseased stem surface and that of leaf rusts as diseased leaf surface. It is customary to speak of stem area and leaf area, rather than “surface.” Wueat Lear Rust Caused by Puccinia triticina Erikss. The period during which wheat leaf rust has been under observa- tion extends from the spring of 1922 through the harvest of 1926. In each of these five seasons, fields of many varieties of wheat were examined in many parts of the state, and careful records were kept and summarized in accordance with the statistical methods previously explained. Each year’s records represent as accurate a statement of the prevalence and severity of leaf rust as could be obtained by sampling, with the means at hand. During the early summer of 1922, before wheat harvest, leaf rust was observed in 139 fields, so distributed as to furnish data applying to the territory shown in black in Figure 4. This being the first season of attempted quantitative recording, it was found later that only 43 of these fields had been sufficiently well examined to allow statistical consideration of the observations. These fields, which were distributed among 17 counties, cOntained 862 acres. In them, an average of 95.4 per cent of the wheat stems bore rust-infected leaves, and an average of 50.6 per cent of the entire leaf area was occupied by pustules. An exceedingly large number of fields were examined in 1923, rec- ords relating to leaf rust being secured from a total of 10,963 acres dis- tributed among the 52 counties shown in Figure 5. In this acreage, the average proportion of stalks bearing rust-infected leaves was 92.0 per cent; in the entire acreage of the counties represented, 91.0 per cent; and for the state as a whole, 89.7 per cent. It was de- termined that the rust pustules occupied an average of 46.6 per cent of the leaf area of every stem in the acreage examined, 33.8 per cent in the county acreage, and 31.3 per cent in the state’s acreage. Records were taken on the prevalence of leaf rust in 1924 from fields containing 8,686 acres. They were distributed among the 68 counties shown in Figure 6. For the acreage involved, an average of 74.6 per, cent of the wheat stems bore rust-infected leaves, and 49.5 per cent of the leaf area per stem was occupied by pustules. When the data were extended to the county acreages, the index of prevalence became 67.4 and that of de- structiveness 19.1; while for the entire state the index of prevalence was 68.3 and of destructiveness 19.1. DISEASES OF GRAIN Crops, 1922-1926 21 Fic.4 1922 Bi i \ Fic.8 1926 Bale YS Fies. 4-8. SOURCES OF WHEAT LEAF RUST DATA, 1922-1926 The black regions on these maps show the territory from which data were taken each year. Nearly 16,500 acres of wheat were examined in the five years. These maps do not represent the distribution cf the disease, which is supposedly . State-wide every year, but simply show the counties in which our observations were made. (See page 20.) 22 Ittrnois NATurAL History Survey BuLLeTIN In 1925 records of leaf rust were taken in fields aggregating 3,225 acres. The fields in which the observations were made were distributed among the 36 counties shown in Figure 7. When the data that were secured were subjected to analysis, the ratio of stalks bearing rusted leaves in the acreage examined was found to be 63.5 per cent and the average amount of rust-occupied leaf area per plant 6.5 per cent. The index of prevalence for the total county acreage represented by the sample fields was 46.3 and the index of destructiveness was 6.0, while for the entire state the indexes were 52.6 and 17.1, respectively. Fields aggregating 1,445 acres and distributed among the 31 counties shown in Figure’8 furnished leaf rust data in 1926. Since agricultural statistics have not yet been provided for this year, it has been impossible to carry out all of the usual computations; but the data secured show in their preliminary analysis, that in the acreage examined 57.2 per cent of the stems carried rusted leaves and 11.2 per cent of the leaf area was occupied by pustules. As a very close agreement has been evident between the indexes se- cured directly from field data and those secured for district and State acreages by indirect computation, the direct indexes for 1926 will be compared in subsequent pages with the computed indexes of previous years. The summarized data for the five seasons are brought into closer comparison in the following table: Prevalence: Caleulated per- Destructiveness: Calculated centages of wheat stems bear- | percentage of leaf area occu- | ing diseased leaves ‘ pied by rust y.,. | Acreage | Year A |examined For the For the | For the county | Pe For the county esis acreage acreage Ee aat acreage | acreage Se sii examined! repre- Seg examined} repre- | Sremiien! acreage Sonited acreage | 5 | : | | 1922 862 | 95.4 94.9 94.1 | 50.6 acl 50.3 1923 10,963 92.0 91.0 89.7 46.6 8 31.3 1924 8,686 74.6 67.4 68.3 49.5 rat Olea: 1925 SRr746) 13.5 46.3 52.6 6.5 .0 atrial 1926 1,445 Dieu ae Sins 11.2 Pe mo I | There is a considerable difference in both the prevalence and the destructiveness of leaf rust between any two years, and there has been a marked and continued decrease in both through the five-year period. The first two of the five years were characterized by very heavy attacks, while in each of the last three years the attack was moderate or light. When considered from the point of view of destructiveness alone, these contrasts are especially evident, but they are borne out in very certain terms also by the corresponding decrease in prevalence. DISEASES OF GRAIN Crops, 1922-1926 23 Oats Crown Rust Caused by Puccinia coronata Corda. The crown rust of oats is essentially a leaf rust, at least under average Illinois conditions, for though it often attacks the stems, infec- tion as a rule does not occur there until a day or two before harvest and usually results in but little damage. Quite early in the season, however, its red pustules appear on the leaves, multiplying rapidly until harvest. Measurements of the destructiveness of crown rust are obtained in exactly the same way, and by employing the same standard, as are those of the leaf rust of wheat (see page 19 and Figure 3). In 1922 crown rust was seen in oat-fields distributed among the 44 counties shown in Figure 9. Data were secured from 705 acres, the re- maining fields not having been sufficiently well examined to give usable information. In this acreage, 78.7 per cent of the stems bore rust infected leaves, 37.6 per cent of the leaf area being occupied by pustules. The field data when applied to the total acreages of the counties which they represented, gave a prevalence index of 69.2 and a destructiveness index of 28.0. The indexes for the State’s acreage are respectively 67.0 and 27.3. The epidemic of 1922 was preceded by an abundant and heavy fall infection on volunteer oats throughout at least the southern half of the state. This infection is known to have extended on the eastern side of the state as far north as Champaign County where specimens of actively sporulating rust were collected as late as the latter part of October. In 1923 crown rust infection was observed in fields located in the 28 counties shown in Figure 10. Fields totaling 1,306 acres were ex- amined, and the records secured in them indicate a prevalence of 93.5 per cent and a destructiveness of 41.2 per cent. For the total county acreage to which the data applied, the indexes were 83.3 and 28.8 for prevalence and destructiveness, respectively, while for the State's acreage they were 83.1 and 30.6. The epidemic of 1923 was early in starting. By June 4 an infection was observed in Jackson County involving an average of 25 per cent of the leaf area on 50 per cent of the stems, and two days later infection was seen in Saline County involving 1.5 per cent of the leaf area on about 10 per cent of the stems. The infection, thus started, spread and in- creased until, by harvest, the heavy epidemic indicated by the figures given above had developed. In 1924, crown rust was observed in fields located in the 33 counties indicated in Figure 11. It is remarkable that the epidemic of this year, as suggested by the map, was confined largely to the northern section of the state, the crop in the south almost completely escaping attack. Field data were secured from 1,080 acres parcelled among 29 counties. The analysis of them indicates that in those fields 79.9 per cent of the oats stems bore infected leaves and that 14.8 per cent of the leaf area was occupied by pustules. The data, when applied to the total county acreage of which they are typical, show a prevalence index of 65.7 and a destructiveness index of 10.7. For the State’s acreage, these indexes are 64.3 and 11.9, respectively. Intinois Narurat History Survey BULLETIN ae rales Lp lees Fics. 9-13. SouRCES OF DATA ON OATS CROWN RUST, 1922-1926 The black regions on each of these maps show the territory from which data were taken in each year of the period. The fields examined contained more than 4,000 acres. (See page 23.) DISEASES OF GRAIN Crops, 1922-1926 25 The rust was late in getting started. All the observations were made during July and August, the earliest July fifth in Adams and Brown Counties, at which time the crop was already ripening. One isolated and very early report from the north (June 27 at Rockford) showed an exceedingly light infection apparently originating from a crown rust infected buckthorn hedge nearby, but elsewhere the usual seasonal de- velopment prevailed. Crown rust was not a very important disease in 1925. Records of its presence were secured only from the 13 counties shown in Figure 12, which lie chiefly in the northern half of the state. The earliest infection was seen near Greenville, in Bond County, where, by June 26, an aver- age of .03 per cent of the stems bore rusted leaves, one leaf on each of these stems having one or two pustules. The fields from which data were secured contained only 297 acres In them, an average of 14.8 per cent of the stems bore rust, only .17 per cent of the leaf area being occupied by pustules. These data may seem to be insufficient for further use, but in view of the very mild attack it is worth while to evaluate them for the greater acreages. For the total county acreages of which they are typical they indicate a prevalence of 28.2 per cent and a destructiveness of .4 per cent, while for the State’s acreage the corresponding figures are 27 per cent and .6 per cent, respec- tively. In 1926, crown rust appeared early. It was found first June 2 near Marshall, Clark County. Throughout the southern half of the state this original infection was so slow in spreading that it never reached heavy proportions; but farther north, after becoming established, it spread rapidly and became exceedingly abundant. As a result, records were obtained chiefly in the north. The fields from which records were taken were distributed among the 20 counties indicated in Figure 13, aggregating 697 acres. In them, 70.4 per cent of the culms bore crown rust and 9.9 per cent of the leaf area was occupied by pustules. Owing to the lack of acreage statistics, the data can not be carried farther to show the prevalence and destructiveness of the disease throughout the state. For closer comparison of the differences in crown rust infections in the years concerned, the data are brought together in the following table: | Prevalence: Calculated per- | Destructiveness: Calculated centages of oat culms bearing percentages of oat leaf area diseased leaves ) occupied by rust pustules - Acreage | Year | examined | Forthe | rorthe For the | Forthe | county States. | Forthe county For the acreage acreage Rats | acreage acreage State's examined repre- = |/examined repre- oats sented aeresec | sented SCECAGG | | ] | | J 1922 705 78.7 69.2 | | 37.6 | 28.0 | 27.3 1923 1,306 937-15),)) |. . B8o3 P. 40520 > + S288 Se is S0s6 1924 | 1,080 1959 65.7 | } 14.8 | 10.7 | o0S9 1925 297 14.8 28.2 AT al -4 -6 1926 697 | 70.4 Saree | | ao | s+ | as | 26 Intrnois NaturaL History Survey BuLLEeTIN No two years show exactly the same indexes, and even when the indexes of prevalence are similar, as in 1922 and 1924, those of destruc- tiveness are quite different. With respect to prevalence, the five years listed fall into two groups, 1922, 1923, 1924, and 1926 showing great prevalence and 1925 slight; but with respect to destructiveness, there is an even more distinct grouping, 1922 and 1923 ranking high and the subsequent years very low. BarLEy LEAF Rust Caused by Puccinia simplex (Koern.) E. & H. The method of measuring the leaf rust of barley is the same as that used in the two leaf rusts just discussed, but since the host crop is confined in a very large measure to the northernmost third of the state (see page 16), the data must be held to apply particularly to that region. Owing to the limited distribution of the barley fields, which are concentrated in the north but occasional elsewhere, data for this disease have not been obtained in the same abundance as for the ones previously discussed. Although in some cases they are too few to be treated statistically, they are summarized here very briefly in order to afford such comparison as they will permit in the latter part of this paper. In 1922, in a single field examined in Boone County 25 per cent of the stems carried rusted leaves, about 5 per cent of the leaf area being rust-covered. This indicates an average destructiveness of about 1.2 per cent. In 1923, a single examination, similar to the one above, made in Ogle County showed a prevalence of 100 per cent and a de- structiveness of 5 per cent. Single fields were examined in 1924 in Kendall, McHenry, Lee, and Ogle Counties. They contained a total of 40 acres, in which 100 per cent of the stems were so lightly rusted that only 4.4 per cent of the leaf area was occupied. Only 1 field furnished data in 1925. In 15 acres near Rockford 5 per cent of the leaf area was occupied by pustules, but the disease was confined to 34.6 per cent of the stems. The data for 1926 were more complete. In the north, records taken from fields in Boone, DeKalb, DuPage, Kane, and McHenry Counties showed 100 per cent of the stems to be rust-infested and 10 per cent of the leaf area rust-covered. Other records were secured in Jackson and Mason counties. Only a trace of rust was found in the first county, but in the second 1 or 2 infected leaves, each bear- ing from one to five pustules, occurred on 13 per cent of the stems. Averages of these data indicate a prevalence of 76.1 per cent and a destructiveness of 7 per cent. The several years compare as follows: Prevalence: Observed Destructiveness: Observed percentage of stems percentage of leaf area Year carrying rust occupied by pustules 1922 25.0 5.0 1923 100.0 5.0 1924 100.0 4.4 1925 34.6 5.0 1926 76.1 7.0 These data, insofar as they are indicative, show fluctuation from DISEASES OF GRAIN Crops, 1922-1926 27 year to year in prevalence, but not equally in destructiveness, for the indexes of the latter were closely similar every year. Rye Lear Rust Caused by Puccinia dispersa Erikss. Leaf rust data can be secured more readily for rye than for barley, not only because tiie rye acreage is greater but also because the fields are more widely distributed. Nevertheless, in comparison with wheat and oats, the acreage is small, and its wide distribution results in fields of small size, except in the small regions especially adapted to its culture, which are characterized especially by sandy soils. In 1922 data were secured from fields located in the seven counties shown in Figure 14. Although taken from a small number of fields, they have considerable weight, both because of their relative uniformity and because of the representative distribution of the fields. A -consider- ably greater acreage of rye was examined for leaf rust in 1923, the fields being distributed among the 13 counties shown in Figure 15. The examinations yielded data of considerable significance, especially because a fairly large number of the fields were located in regions of intensive rye culture. The season of 1924 provided data much more complete than any other year included in this report. The 48 counties shown in Figure 16 each furnished data from one or more fields, the fields examined reaching 73 in number and containing a total of 393 acres. Fields located in the 11 counties shown in Figure 17 furnished data on rye leaf rust in 1925. With the exception of Morgan County, where three fields were examined, observations were made in one field in each county. The wide distribution of the counties, however, gives weight to the data, particularly since important rye sections are included. While very little data could be secured in 1926, several small fields were examined in the 4 rather centrally located counties shown in Figure 18. The results of the field examinations, as shown by an analysis of the data, are briefly as follows: Prevalence: Calculated per- Destructiveness: Calculated centages of rye stems bearing percentages of rye leaf area rust infected leaves occupied by rust = hae Acreage Year |examined For the For the For the county z For the county | acreage acreage For the acreage acreage For the examined repre- | State examined repre- State sented | sented fi | | l | « 1922 97 17.2 Arlee CL al | 46.4 34.0 | 55.1 1923 217 Buea te SV EReR Has SOS 12.0 ee 8.2 1924 393 39.7 | 45.0 *22.2 6.3 2.7 | 2.0 1925 230 75.0 30.9 44.5 1:9 0.6 0.9 1926 23 UG)Sil | Sais Sis | a he | ax ean | | | Here, as in the cases of the rusts previously discussed, there is variation in both prevalence and destructiveness from year to year. 28 Inuinois NAturAL History Survey BuLietin Fies. 14-18. Sources OF RYE LEAF RUST DATA, 1922-1926 The black regions on these maps show the territory from which data were taken in the years making up this period. There were, in all, 960 acres in the rye fields examined. (See page 27.) DISEASES OF GRAIN Crops, 1922-1926 29 a Poe tel Ft ¥ Fic. 20 1924 Fic. 21 1925 Fic. 22 1926 Fics. 19-22. SourRcES OF CORN RUST DATA The black regions on these maps show, respectively, the territory from which data were taken in 1922 and in the period 1924-1926. In 1923, data were obtained in Douglas, Effingham, and McLean counties only. (See page 30.) 30 Intrnois NATurRAL History Survey BuLLeTin This rust has been, on the whole, much milder than the other leaf rusts, the season of 1922 being the only one in which a really destructive at- tack occurred. The yearly variation appears to have been concerned with prevalence more than with destructiveness. Corn Rust Caused by Puccinia sorghi Schw. Corn, the most important both in yield and acreage of all the cereals grown in Illinois, is subject to the attack of but one rust. It is a leaf rust. In securing data on corn rust, the only phase of the attack that has been studied is prevalence. The intensity of the attack is exceed- ingly hard to estimate, first because of the large size of the corn leaf, and second because the pustules occur very sparsely on the leaf and only in limited spots. No means for estimating the severity of the attack has yet been devised. In 1922, corn rust was not very prevalent. As a result, data were secured only from the 6 counties shown in Figure 19, the small acreage represented being located entirely in the northern half of the State. The data, though meagre in comparison with other years, were nevertheless representative. Even less abundant in 1923 than in the previous year, rust was recorded in only three fields, one in Douglas, one in Effingham, and one in McLean Counties. If the infection in these fields was typical of that throughout the State, the prevalence would be expressed as 3 per cent. An abundance of data was obtained in 1924. In the 60 counties shown in Figure 20, data were taken from 84 fields aggregating 3762 acres. For 1925 the data are less copious than for the preceding year, but the 17 counties shown in Figure 21 contributed records from fields aggregating 450 acres. Exactly 70 fields, distributed among the 63 counties shown in Figure 22, furnished data in 1926. Rust prevalence was exceedingly variable, being very high in some districts and very low in others. The data for the 5 years are brought together in the following table for more intimate comparison. Prevalence: Calculated percentage of corn stems bearing rust-infected leaves Acres Year examined For the acreage For the county examined acreage concerned For the State | | 1922 115.7 41.8 | 42.2 34.6 1923 40.5 3.0 | | 1924 3,762.0 63.0 | 61.0 62.6 1925 450.0 26.6 | 30.0 | 33.3 1926 1,333.0 11.4 | | | DISEASES OF GRAIN Crops, 1922-1926 31 - Although prevalence only has been recorded, a difference from year to year is evident. It is remarkable that the greatest prevalence occurred in 1924, succeeding the year of least prevalence. Comparison of all leaf rust data In the preceding pages the yearly indexes of prevalence and de- structiveness shown by data taken directly from cultivated fields have been given for the several leaf rusts. As they were considered, it be- came apparent that, though year-to-year variation was a common charac- teristic, the particular years of greatest and least intensity of attack were not the same for all. This fact is brought out more clearly in Figures 23 and 24. The indexes of prevalence for the entire state, as listed in the foregoing tables (see pp. 22-30), are shown graphically for all the leaf rusts in Figure 23. The year 1922 appears to have been very favorable to the leaf rusts of wheat, oats, and rye, but unfavorable to those of x xy) v S .) S N X X a. Fic. 23. PREVALENCE OF CEREAL LEAF RUSTS, 1922-1926 The prevalence indexes computed for the leaf rusts from field data and given in tables in the text are shown graphically here. The wide differences in the prevalence of these rusts in each year and in the trend of prevalence from year to year suggest that there is a particular combination of weather conditions most suitable for the maximum prevalence of each rust. (See page 32.) it) bo Inuinoris NAturaAL History Survey BULLETIN corn and barley. The following year, 1923, was somewhat less favor- able for wheat leaf rust and very much less favorable for the corn and rye rusts, while the oats rust found better conditions and the bar- ley rust attained its maximum prevalence. The general trend in 1924 was downward, as compared with 1923, although the barley leaf rust maintained the high prevalence of the previous year, and corn rust found the best conditions of any of the five years. Rye leaf rust, alone of the five, was able in 1925 to increase its prevalence over that of the preceding year, the four others showing very marked decreases. Definite increases in prevalence were shown by the barley, oats, and wheat leaf rusts in 1926, while those of corn and rye decreased beyond their low points of the year before. Through the five years to which these records apply, the same trend of prevalence has been followed by the leaf rusts of barley and oats in one instance, and of wheat and rye in another; but corn rust has had an individual trend, quite distinct from either of the two other groups. It is especially noteworthy that in no one year did the prevalence indexes of all move in the same direction. In contrast with the foregoing is the fact, illustrated in Figure 24, that through all of the four years previous to 1926 the general trend of destructiveness was downward, ranging from severe attacks in 1922 and 1923 to mild and insignificant attacks in 1924 and 1925. With the exception of wheat leaf rust, a general upward trend is apparent for 1926. © v S “4 % N ® & i R w g Q Fic. 24. DESTRUCTIVENESS OF THE CEREAL LEAF RUSTS, 1922-1926 The indexes of destructiveness computed from field data and given in tables in the text are shown graphically here. Since 1922, the general trend has been downward; but crown rust increased in 1923 and 1926, and barley leaf rust in- creased in 1926. DISEASES OF GRAIN Crops, 1922-1926 oo a) The Stem Rust of Cereals Caused by Puccinia graminis Pers. Although each of the cereal crops grown in Illinois has an in- dividual leaf rust, the stem rust is the same for all, attacking all but corn. Special races of the stem rust exist, however, which are so lim- ited in their ability to attack that each occurs on one crop only. The varied requirements of each crop in length of season and planting and growing periods present diverse conditions for the development of stem rust epidemics on each crop. Hence, it is not likely that the same phe- nomena of prevalence and destructiveness will be exhibited by this rust upon any two crops in a given year. It is necessary, therefore, to treat the stem rust on each crop as though it were a separate rust. The method of measuring the prevalence of stem rust is similar to that used for the leaf rusts. Instead of individual plants, individual stems are taken as units, and prevalence is computed according to the method described on pp. 6-8. Destructiveness is expressed in terms of stem area occupied by the rust pustules, and the standard shown in Figure 3 is used as described on pages 18 and 19 as a measure of stem area. THE STEM Rust ON WHEAT At the time field work was begun in 1922, stem rust infection was already widely prevalent on wheat. Its occurrence was demonstrated in the 30 counties shown in Figure 25. Although no definite records of prevalence or severity were secured from the southern territory marked on the map, data were taken from 17 fields in the northern part of the state, and the destructiveness indicated by them agrees well with thai shown by the specimens collected in the south. The earliest record of infection in 1923 was made June 4 in Jack- sen County. Isoated infections such as those subsequently found Tune 7 in Bond County, June 12 in Franklin County, and June 14 in Hamliton and White Counties served as foci from which, about June 16, disease dissemination began; and by June 22 the epidemic had become general. Data were secured from 72 fields distributed among the 39 counties shown in Figure 26. The extent of the territory from which the data were secured is particularly fortunate, in view of the intensity of the rust attack. During 1924 stem rust was more prevalent in the north than in the south. Data were secured from 61 fields parcelled among the 31 counties shown in Figure 27. The original infections took “place at least 8 days later than was the case the year before, and the period of moderate temperatures was so curtailed in the south that only a mild epidemic resulted there. So rare was stem rust during 1925 that only six records of it were obtained. The fields from which these records were taken were located 34 Ittino1is NAturAL History Survey BULLETIN Fics. 25-29. SouRCES OF STEM RUST DATA FOR WHEAT, 1922-1926 The black areas on these maps show the regions from which the data dis- cussed in the text were taken in each year. The fields from which records were taken during the five years contained 3,851 acres. (See page 33.) DISEASES OF GRAIN Crops, 1922-1926 35 in the counties shown in Figure 28. A recrudescence of stem rust oc- curred in 1926, which, by comparison with the light attack of the previous year, gave rise among wheat growers to grave fears of damage, fortunate- ly not realized. During the season data were taken from 27 fields located in the 19 counties shown in Figure 29. As in previous years, abundant infection was found less readily in the south than in the north. The variations in prevalence and destructiveness alluded to in the foregoing paragraphs are illustrated in the following table, in which the final figures arrived at in the statistical analyses of the data are brought together. | Prevalence: Calculated per- Destructiveness: Calculated | centage of diseased stems percentage of diseased stem area _ | Acreage 7 - Year | examined For the For the | For the county For the For the county | For the fields acreage State's fields acreage | State’s recorded repre- | acreage recorded | repre- | acreage sented | sented | 1922 256.5 “9 «2 22.06 1.8 32.8 17.8 1923 2,305.8 0 4 35.7 8.1 Meare: 8.0 1924 659.0 .0 sli ualeal me 0.5 0.6 1925 90.0 -8 4 14.9 2.1 0.6 1.2 1926 540.0 -8 35 ae ele he Bic | I The figures relating to the epidemic of 1922 are very inconsistent, showing much too wide a divergence in the separate columns of the table relating to both prevalence and destructiveness. This is due to exceedingly uneven weights given, of necessity, to the observations, in terms of the acreages to which they apply. It was to be expected, how- ever, that in the first season of quantitative measuring of disease abund- ance some such discrepancies would appear. Since the indexes of prev- alence and destructiveness secured for the acreage examined are more in harmony with those secured in subsequent years and with the general trend of the notes taken, they will be used in later discussions. The figures for the remaining years are generally consistent, not only for the acreage examined, but also for the county acreage repre- sented and for the State’s acreage. They illustrate variation in both prevalence and destructiveness, and they show in a very emphatic way the fact that, of the two wheat rusts, stem rust has been the less significant. THE Stem Rust oN Oats In 1922 stem rust was prevalent on oats only in the northern part of the state. Its presence was observed in the 17 counties shown in Figure 30, but usable data were secured from only 14 fie'ds in counties located in the extreme west and north. So rare was infection of oats during 1923 that not one specimen of stem rust was collected. No 36 Intino1is NAturAL History SurvVeY BULLETIN notes or data of any kind could be secured to show either its relative prev- alence or destructiveness. As more than 1,300 acres of oats were examined without a single stem rust infection being found, the indexes of prevalence and destructiveness may be considered as zero for the year. In contrast with the preceding year, in 1924 oats throughout the State were abundantly infected. The infection was particularly heavy in the northern half of the State. Fifty-eight fields distributed among the 34 counties shown in Figure 31 furnished data on prevalence and destructiveness. Again in 1925, the oats crop was infected throughout the northern half of the State. Data were taken from 8 fields in the seven counties shown in Figure 32. Although apparently inadequate in total acreage, the fields were widely distributed and were representa- tive, to that extent, of the entire oats acreage. Data were taken from 42 fields in 1926, these fields being scattered among the 29 counties shown in Figure 33. They were representative to a remarkable degree of the oat acreage of the State. Stem rust was very abundant, and quite destructive in the northern counties, as com- pared with previous years. The indexes of prevalence and destructiveness for the five years are brought together in the following table. — | Prevalence: Calculated per- Destructiveness: Calculated | centage of infected stems percentage of stem area occu- | pied by rust 2 Acreage j Year /examined For the | For the For the county For the For the county | For the | acreage acreage State’s acreage acreage State’s | examined repre- acreage examined repre- acreage sented sented | | 1922 232 27.7 54.7 56.9 14.6 25.8 29.0 1923 1,306 0 0 0 0 0 0 1924 1,079 41.6 38.1 45.5 8.8 13.8 13.8 1925 162 27.8 26.3 21.6 6.7 5.1 4.5 1926 728 85.5 B eee: notre 42.7 aes | Roa The variation exhibited by the indexes recorded above for 1922 is to be expected, partly because of lack of experience in measuring the quantity of rust and partly because of the very limited distribution of the fields from which data were taken. In their computation the southern part of the state was not represented. For the other years, the in- dexes, though modified in accordance with the extent of the territory to which the data are applied, are consistent and representative, giving by comparison with each other a fairly accurate depiction of the in- fections in each year. DISEASES OF GRAIN Crops, 1922-1926 w -~1 Fic. 30 1922 Fic. 31 1924 Fies. 30-33. SOURCES OF STEM RUST DATA FOR OATS The black areas on these maps show the regions from which the data dis- cussed in the text were taken in 1922, 1924, 1925, and 1926. No infection was found in 1923, though more than 1,300 acres were examined. The fields exam- ined in the other four years contained a total of 2,201 acres. (See page 36.) 38 Intinois NAturaL History Survey BULLETIN THE STEM Rust ON BARLEY Very few records of the occurrence of stem rust on barley have been made in Illinois south of the. north third of the State. So far as the annual epidemic on barley is concerned, only the northern third of the State needs to be considered, not only because of the rarity of the rust southward but also because of the scarcity of the crop there. Because of the limited range of the crop and the limited acreage devoted to it, records of its diseases are much fewer than those for more common and more widely grown cereals. In 1922 infection was found in the five counties shown in Figure 34. Data were obtained from eight fields which were representative of the barley district. Stem rust appeared to be completely absent in 1923, but in 1924 the infection became very general in the north. During the latter season, one barley field was examined in each of the 15 counties shown in Figure 35. In 1925, fields were examined in the four counties shown in Figure 36, and stem rust was found to be prevalent, though in a very light form, in each. By the time the observer reached the barley region in 1926 the crop had been cut and was standing in shocks. Although examinations made under these conditions are not wholly satisfactory, one field in each of the three counties, Boone, DeKalb, and McHenry, was given a very careful examination; and the data taken from them may be considered typical of the stem rust infection in the barley region. The indexes of prevalence and destructiveness secured from the computations made with field data are as follows: Prevalence: Calculated per- | Destructiveness: Calculated | centage of. stems infected with | percentage of stem area occu- stem rust | pied by rust = Acreage ; f Year |examined | For the | For the For the county For the For the | county For the acreage | acreage State’s acreage | acreage State’s examined repre- acreage examined | repre- acreage | sented | | | sented | | | | 1922 52 14.1 | 48.1 45.5 | 5.8 12).3 12.4 1923 ce 0 | 0 0 0 0 0 1924 194 5.6 | Ho) 8.0 ay -5 6 1925 65 Lit 11.3 iil al if 2 2 1926 60 100.0 Sse ete 28.7 | Be 3 The figures given above, which are reliable indexes of the serious- ness of stem rust on barley during each of the five years 1922-1926, indicate definitely the relative importance, in each year and throughout the period, of this rust and the leaf rust (see page 26) as agents in reducing the barley yield, stem rust being in the main much the less significant. DISEASES OF GRAIN Crops, 1922-1926 39 Fics. 34-86. SOURCES OF STEM RUST DATA FOR BARLEY The region from which data were taken in the years 1922, 1924, and 1925 are shown in black on these maps. In 1923, there was no stem rust infection. In 1926, 3 fields, one in Boone, one in DeKalb, and one in McHenry County, were examined. (See page 38.) 40 Ittinois NAturAL History Survey BuLLETIN Tue STEM Rust oN RYE In spite of the wide distribution of rye in Illinois and the ex- tensive use of it along newly placed hard roads, which might be ex- pected to aid in distributing stem rust infection on the crop, it has been possible to secure but very little data on stem rust prevalence in rye fields. In 1922 only two fields, one in Mason and one in Grundy County, were found infected. No infection was recorded in 1923. In 1924 data were secured from 10 fields located in the seven counties shown in Figure 37. During the two subsequent years, 1925 and 1926, no instance of infection was seen in any of the fields examined, though Fic. 37. SOURCES OF STEM RUST DATA FOR RYE IN 1924 In the seven counties shown in black, 10 fields containing a total of 70 acres furnished data on the stem rust attack of 1924. infected rye plants were found occasionally in wheat fields and along roadsides. The data on the severity of stem rust on rye for the years covered by the survey are as follows: Prevalence: Calculated per- Destructiveness: Calculated centages of stems infected percentage of rye stem area | with stem rust occupied by stem rust | Acreage | | Year jexamined’ For the | | For the For the county For the For the county For the acreage acreage State’s acreage acreage State’s examined repre- acreage examined repre- acreage sented sented 1922 70 50.0 50 50 28.5 22.5 25.5 1923 217 6 0 0 | 0 0 1924 70 (fet 18.1 25.9 3.9 S) al 13.9 1925 230 0 0 0 0 0 0 1926 23 0 0 0 0 0 0 DISEASES OF GRAIN Crops, 1922-1926 41 Comparison of stem rust infections on the cereal crops subject to its attack With stem rust, as with leaf rust, both the degree of prevalence and the degree of destructiveness have varied from year to year. These variations, which have not been of the same relative amounts for each of the crops, are best shown graphically. The indexes of prevalence on each of the cereals, for each year from 1922 through 1926, are shown in Figure 38. A common trend is shown by all except wheat. In 1922 stem rust was moderately prev- alent on barley, rye, and oats, but only mildly so on wheat. The fol- lowing year prevalence dropped practically to zero on the first three crops, but on wheat it increased considerably. The crop season of 1924 saw a marked increase on all the cereals except wheat, while in 1925 prevalence was less on oats and rye, but more on wheat and barley, S 8 a S % v aS v R G S Ng 2 Q N S Fig. 38. PREVALENCE OF STEM RUST ON THE CEREAL CROPS, 1922-1926 The indexes of prevalence computed from field data and given in tables in the text are shown graphically here. There is a greater uniformity of prev- alence trend from year to year on all crops than was true with the leaf rusts (compare with Fig. 23); but in contrast with the prevalence of the leaf rusts, stem rust reached its highest point in 1926. 42 Intinois NAturAL History Survey BuLLEeTIN than the year before. In 1926 it increased markedly on all except rye, reaching the greatest degree recorded during the survey. It is evident from an inspection of Figure 38 that the climatic conditions of any one year have not affected the prevalence of stem rust to the same extent, or in the same way, on every crop. The intensities of attack, as indicated by the indexes of destruc- tiveness calculated from the field data, are shown in Figure 39. Prac- tically the same tendencies are exhibited on all the crops, wheat alone showing a marked divergence. In 1924, when the trend of destruc- tiveness was upward on the three other crops, it declined very markedly on wheat. There has been a distinct parallel between prevalence and destruc- tiveness throughout the five seasons, the only break in it being the at- tack on wheat in 1923, in which year the increase in prevalence over the previous season was accompanied by a large decrease in destructiveness < v v S Hy y S S C > A w @ Q Fic. 39. DESTRUCTIVENESS OF STEM RUST ON THE CEREAL CROPS, 1922-1926 The indexes of destructiveness given in tables in the text are shown graph- ically here. The trend of destructiveness from year to year follows very closely the trend of prevalence (compare with Fig. 38), being greatest in 1926 and 1922, and generally very low in the other years. DISEASES OF GRAIN Crops, 1922-1926 43 CEREAL SMUTS All of the cereal crops are subject to diseases classed under the general name, smut; but the smuts, like rusts, are different on the dif- ferent crops, exhibiting different symptoms and being possessed of dif- ferent means of spread and infection. On wheat there are three; on barley, two; on oats, two; on rye, two; and on corn, one. According to their appearance, they can be classed as “loose”, “covered”, and “stripe” smuts. In general, “covered” smuts are much less abundant than “loose” or “stripe” smuts. The covered smuts of oats and bar- ley, because of their rarity, have not furnished sufficient data to de- serve inclusion in this discussion; and the limited range of the “stripe”, or “flag”, smuts on wheat and rye precludes their inclusion. The outstanding characteristic of all the smuts, except the one on corn, is that they nearly always destroy completely, either directly or indirectly, the head or the grain. The loose smuts replace the grain and the floral glumes with a mass of smutty powder, the covered smuts replace the grain and often the floral glumes as well, and the stripe smuts produce such malformations of the leaf and head that diseased stems rarely are productive. As a result, the prevalence of a smut is also a direct measure of its destructiveness. Wueat LoosE SMUT Caused by Ustilago tritici (Pers.) Rostr. This is the least important of the common cereal smuts. Though distributed throughout the wheat fields of the State and conspicuous enough to be classed among the common diseases, its means of ac- complishing infection, which is limited to the very short time the wheat flowers are open, prohibits it from becoming abundant, at least under Illinois conditions. For the same reason, the extreme fluctuations ex- hibited by other diseases will not be found with it. During 1922, loose smut was seen in wheat fields located in the 29 counties shown in Figure 40, Wheat harvest was already so far advanced when the examinations were made that only the northern fields furnished data. Data secured in 1923 from 81 fields located in the 38 counties shown in Figure 41 were representative of the loose smut infection of the season, not merely because of the large wheat-acreage from which they were taken but also because of their extensive distribution and _ their location in regions both of intensive and less intensive wheat culture. The most abundant data obtained in any of the five years of the survey were procured in 1924. In the 58 counties shown in Figure 42, 145 wheat fields aggregating 5,661 acres were examined. The wheat grown in the counties represented by the field records aggregates 1,754,835 44 Int1nois NaturALt History Survey BULLETIN Fic. 40 1922 Fic. 41 1923 Fies. 40-44. Sources OF DATA FOR THE LOOSE SMUT OF WHEAT, 1922-1926 The black areas on these maps show the regions from which data were taken in each year of the period. The fields examined in these five years contained a total of 16,425 acres. (See page 43.) DISEASES OF GRAIN Crops, 1922-1926 45 acres, which is slightly more than 76 per cent of the State’s acreage for that year. Data were obtained in 1925 from 51 fields located in the 26 counties shown in Figure 43. Although the acreage they contained was only about one third as great as in the previous year, the total county acreage of which they were representative constituted nearly 29 per cent of the State’s acreage. In 1926, data were obtained by. examining 48 wheat fields located in the 29 counties shown in Figure 44. Though somewhat less repre- sentative with respect to size of acreage and wideness of distribution than the records of the previous two years, the increased care employed in obtaining them makes them the most dependable of all the estimates obtained. During these five seasons, data have been taken from 549 wheat fields containing a total of 13,425 acres. The indexes of prevalence obtained from the analysis of the data compare as follows: | Prevalence: Calculated percentage of wheat heads | infected with loose smut | é | Acreage oes = — Year | examined | In the acreage | In the county In the | examined acreage represented , State’s acreage | | | | 1922 | 433 | BY | Ty | 89 1923 | 4,421 | 1.41 | 1 | 1-39 1924 | 5,661 | 44 | | 45 1925 | 1,725 | 67 | | 70 1926 | 1,185 | .94 | | Jos | | | Wueat Bunt Caused by Tilletia laevis Kuehn. Wheat bunt, known more commonly as stinking smut, is much less prevalent than loose smut in the wheat fields in [llinois. Usually only a comparatively small number of wheat fields in a county are infested, and they often are grouped together in a small region. In the in- fested fields bunt may be the most costly disease, for it not only destroys the heads on infected stems but gives so bad an odor to the harvest from the field that Jarge discounts, called dockage, from the market price are applied when the grain is sold. The field prevalence of bunt is not easy to determine. The heads on diseased stems, though often very characteristically malformed and discolored, are yet so nearly like the normal heads that even a trained eye does not recognize them readily. Moreover, the characters by which they can be recognized do not develop fully until a field is nearly ripe. As a result, data on prevalence rarely is obtained earlier than a 46 Inyinois Natura History Survey BuLLETIN few days before harvest. The fields in which it is found are, there- fore, both small in number and not representative in distribution, and the data obtained from them are, very probably, understatements of the amount of infection. The only means of supplementing the field counts is to obtain reports from wheat dealers on the marketing of smut in- fested wheat. In analyzing data on bunt prevalence, the procedure is not quite the same as for other diseases. The smallness of the amount of data secured from fields, together with their limited distribution, renders them incapable of complete analysis. As a rule the only figure which can be computed is an index of prevalence in the acreage known to have been infested. It can be considered only as typifying the amount of in- fection prevailing in the crop found by other means to have been in- fected. The most useful data on bunt prevalence have been obtained in re- ports from grain dealers. Circular letters were sent annually to the dealers in the State, requesting reports of the number of bushels pur- chased and offered that were smutted; and the replies received, which have been more numerous than is usual with circulars, are believed to be especially dependable because the dealers were asked to reply only when such lots had been offered them. The data secured in this way, being in terms of bushels rather than acres, require a treatment somewhat different from that accorded acreage statistics. The following short section taken from the analysis of the 1922 reports shows the method. h Percentage of Sheet County ous ets evereee County yield the county yield infested | 1 Adams 0 1,011,030 0 3 Champaign 0 4 Champaign 2,000 5 Champaign 0 6 Champaign 622 7 Champaign 0 2,622 518,315 -506 8 Douglas 1,500 ) {Douglas 0 1,500 392,632 -382 30 Piatt 2,000 31 Piatt 500 2,500 581,600 | .430 | 32 Putnam 2,000 203,381 .983 Total | 8,622 2,706,958 | .318 The dealers’ reports are assigned places in the permanent file with other disease records. These for each year are kept in separate folders, DISEASES OF GRAIN Crops, 1922-1926 47 the sheets being assorted by counties as are the other reports, and the sheets of each folder numbered serially. In the calculations made with the data, only one tabulation is made. In the first column, the number of the report sheet is entered; in the second column, the county from which it came; and in the third column, the number of bushels of smut- infested wheat. When this is completed, the number of bushels in- fested is obtained for each county and for all the reports by summing the items in column 3. In column 4, opposite each county total, the county yield given in the agricultural statistical reports already mentioned is entered. The total yield of all the counties concerned in the report is the sum of these entries. By dividing the county yields by the county totals of infested wheat, a percentage, shown in column 5, is obtained which represents the proportion of smut infestation for each county ; and by dividing the sum for column 3 by that for column 4 a per- centage is obtained which represents the average proportion of smut infestation for all the counties in the tabulation. The percentages are carried to the third place beyond the decimal for the reason that the per- centages dealt with in this disease are always very small and the maximum of accuracy is desirable. No further manipulation of these data is permissible, They must be considered as representative of the entire territory from which they came, and the complete lack of data from other territories prohibits further calculations. The figures secured by this method are empirical in that they rep- resent prevalence less directly than definite field data. A more definite conception of prevalence can be obtained if the results of field examina- tions and of dealers’ reports are taken together. For example, dealers’ reports show that, in 1922, .371 per cent of the State’s yield was in- fested, the fields in which the infestation occurred having, according to the results of field examinations, 1.2 per cent of the heads bunt-in- fected. During 1922 data on field prevalence were secured in six counties. These, together with dealers’ reports, gave information from the 17 counties shown in Figure 45. The infestation present in 30.8 per cent of the State’s yield of 55,432,000 bushels is represented. The field data secured in 1923 are the most extensive obtained dur- ing the survey. Definite records were taken in 40 fields located in 24 widely distributed counties; but the acreage of these fields—2123 acres in all—is less than .2 per cent of the total acreage in the counties in which they were located, emphasizing again the lack of general prev- alence. Grain dealers’ reports received from 48 counties, give data on 64.7 per cent of the yield of the State. The counties in which bunt was shown to have occurred, by field examinations and dealers’ reports, number 35 and have the distribution shown in Figure 46. From the two sets of data, it may be inferred that fields furnishing 317 per cent of the State’s yield were bunt-infested to the average extent of 2.5 per cent. Field examinations made in 1924 revealed the presence of bunt in 14 widely scattered counties Reports for this year were received from 48 ILLInois NATURAL History SURVEY BULLETIN Fic. 1923 Fic. 48 1925 Fies. 45-49. Sources OF WHEAT BUNT DATA, 1922-1926 The black areas on these maps show the territory from which data were taken in each year of the period. The data for this disease are obtained in part by direct examinations of fields, and in part from the reports supplied by grain dealers. During the five years of survey, data were taken from fields aggregating 2,785 acres. The dealers’ reports applied to from 30.8 per cent to 64.7 per cent of the State’s annual yields. (See pp. 45-47.) DISEASES OF GRAIN Crops, 1922-1926 49 grain dealers in 46 counties. The total distribution of bunt included the 34 counties shown in Figure 47. The lack of adequate assistance in the survey during the summer of 1925 made it inadvisable to circularize the grain dealers, but data were secured by carefully examining seven bunt-infested fields in the seven widely scattered counties indicated in Figure 48. Although the number of fields is small and their acreage almost negligible, their wide distribution and the variation in degree of infestation which they exhibited justify considering the data as representative. Field examinations showing bunt prevalence in 1926 were limited, including five fields, all of which were in four centrally located counties. However, grain dealers’ reports were abundant. Responses to inquiries were received from 193 purchasing stations, the crop directly repre- sented by these reports constituting a very large percentage of the State’s yield. The range of bunt infection for the year, compiled from dealers’ reports and field examinations, is indicated in Figure 49, which shows this disease to have occurred in 44 counties. Summaries of the data showing field prevalence and the infes- tation of harvested grain are given in the table below. Prevalence, as shown by: Field examinations Grain dealers’ reports Year ie l Acres Average Bushels of Fereentane! oF examined percentage of marketed wheat | wheat smut- heads diseased represented | infested 1922 107 1.20 | 17,085,896 371 1923 2,123 2.50 | 128,104 -317 1924 310 4.03 | 25,150,705 | 1.043 1925 105 1.43 Pa Ds erica tL aad a a mere roece 1926 140 Pipi en lee Ce Mmenenierrcoce re lla sve | Oats Loose SMuT Caused by Ustilago avenae (Pers.) Jens. The loose smut of oats, though having a life history different from that of the loose smut of wheat, appears much the same in the field. It destroys the spikelets, leaving in their stead masses of smutty powder. Its abundance is measured simply as the percentage of smutted heads. During 1922, dependable records of its prevalence were secured from 39 oat fields located in the 20 counties shown in Figure 50. It is unfortunate that all of these records should come from the northwest quarter of the State, but some dependence may be placed upon them because their number, distribution, and their varying acreages seem to indicate conditions typical of a very large part of the State. Data showing loose smut prevalence in 1923 were secured from 88 fields aggregating 1,695 acres and distributed among the 36 counties 50 ILLINOIS NATURAL History SuRVEY BULLETIN Fic. 50 1922 Fic.51 = 1923 Fic. 53 1925 Fies. 50-54. SourcES OF DATA FOR OATS LOOSE SMUT, 1922-1926 The black areas on these maps show the territory from which data were taken in each year. In all, fields totaling 7,667 acres were examined, the small- est acreage (723) being examined in 1922, and the largest (2,412 acres) in 1924. (See page 49.) DISEASES OF GRAIN Crops, 1922-1926 51 shown in Figure 51. The extent of the regions from which the records were taken make them much more representative than those of 1922. An acreage still larger than that of 1923 furnished data on oats smut prevalence in 1924. In all, 135 fields containing 2,412 acres were examined. They had the distribution shown in Figure 52, which in- cludes 57 counties so widely scattered as to be typical of the entire state. The acreage in these counties constitutes 64.7 per cent of the State’s acreage. The acreage examined for smut in 1925, though less than that of 1924, was close to 2000. In the 48 counties shown in Figure 53, data were taken from 104 fields, which may be considered typical of the in- fection throughout the state even though a considerable territory in the northwest is not represented directly. In 1926, 41 oats fields were examined for smut prevalence. Though their total acreage was small when compared with previous years, they were widely distributed and were directly representative of the oats crop grown in the 32 counties shown in Figure 54. These counties are so distributed as to be typical of the entire state. The indexes of prevalence, which in these cases are also indexes of destructiveness, obtained from the field data are given below for each of the 5 years. Prevalence: Calculated percentage of smut in- | fected oats heads Acreage | Z ey | ey ear |/examined For the | | For the For the county For the Forthe | county For the acreage acreage State’s acreage acreage | State’s examined repre- acreage examined repre- | acreage sented | sented | | 1922 193 8.84 2.54 2.43 Taare ie a ean 1923 2,164 4.22 5.65 Sieh Mieercicrcme eile miata eee RoE 3,166 6.18 4.16 TSC UEy ON ey el eran 9 125 16.36 84.74 21.20 14.51 34. 2 1926 435 WH ol Saco Ul Ne Sado 2.08 os | Ps 58 Intinors NATuRAL History SurvEY BULLETIN Fic. 65 1922 ais a a Fic. 69 1926 Fries. 65-69. Sources OF DATA FOR SCAB ON WHEAT, 1922-1926 The black areas on these maps show the regions from which scab data were taken by direct examination of wheat fields in each year. A very large number of fields were examined, data being taken directly from a total of 6,083 acres (see page 57.) on ~) DISEASES OF GRAIN Crops, 1922-1926 Scas ON Oats Although large acreages of oats have been examined in each of the years of the survey, but few data have been accumulated on scab in- fection. During 1922 one infested field was found in Stephenson County, and in 1923 an infested field was found in Logan County. In 1924 scab was sufficiently prevalent to show, on the basis of the data taken from 5 fields located in the four counties shown in Figure 70, an average preva- lence of .75 per cent and a destructiveness too small to be determined. The fields furnishing these estimates contained an even hundred acres. In both of the two seasons, 1925 and 1926, scab was so rare on oats that it was neither collected nor recorded. The prevalence may be stated for the five years as follows: Percentage of panicles Year Acres examined infected 1922 723 Trace 1923 1,695 Trace 1924 100 -75 1925 1,967 0 1926 870 0 Fig. 70. Source OF THE DATA FOR Fic. 71. Source OF THE DATA FOR SCAB ON OATS, 1924 SCAB ON BARLEY, 1924 The black areas on this map Although a considerable acre- show the regions from which scab age of barley was examined in each data were taken by direct examina- year of the period 1922-1926, data tion of oats fields in 1924. In the on scab were obtained only in 1924. 5,355 acres of oats examined during In the other years infection was the period 1922-1926, scab was prac- practically absent. tically absent, except in 1924. ScAB ON BARLEY As was the case with oats, infection has been very light on barley during the years of the survey. Only in 1924 was it possible to secure positive data on its prevalence. In this season, 30 fields were examined. ‘They were located in the 20 counties shown in Figure 71 and contained 60 Intinois NATurAL History Survey BuLietin a total of 392 acres. Their location in the northern counties of the State makes them typical of the barley region. In fact, the 209,780 acres of barley which they represented directly, were slightly more than 93 per cent of the State’s acreage. In these fields, the data indicate a prevalence equal to 13.43 per cent; in the acreage directly represented, they indicate an average prevalence of 12.77 per cent; and in the State, of 12.86 per cent. During 1925 and 1926 scab was so rare in barley fields that no rec- ords of it could be taken. ScAB ON RYE In contrast with the infections on oats and barley, scab on rye was most abundant in 1923, though the attack was too mild to measure. In the seasons of 1922, 1924, 1925, and 1926, infected rye was found only as mixtures in wheat fields. Summary of data on cereal scab The data obtained in field examinations, though much less voluminous than those for other cereal diseases, indicate the variations in prevalence among the individual crops from 1922 through 1926 and the intensity of the attacks in 1925 and 1926, The summaries of prevalence only, arrived at by methods previously outlined and given above for each of the crops, are compared in Figure 72. Besides indicating that, of the four cereals commonly attacked by scab, wheat and barley alone have had serious epidemics, Figure 72 /ndex i 70: v S LY S ry x Q Fic. 72. PREVALENCE OF SCAB ON CEREALS, 1922-1926 The prevalence indexes for scab calculated from field data and given in the text are shown graphically here. Wheat and barley have had serious infec- tions, and wheat alone is diseased every year. DISEASES OF GRAIN Crops, 1922-1926 61 shows that scab, like other diseases, finds conditions in a given year more favorable for spread on one crop than on another. Thus, in one season it may be very prevalent on wheat but practically absent from the other crops. Wheat appears to be the only crop consistently susceptible. There was an increase in prevalence on oats and barley in 1924; but, in contrast, the prevalence on wheat diminished. The slight rise in prevalence on rye in 1923 was accompanied by an increase on wheat. Except for these two coincidences, the tendency toward an increase in scab prevalence on one crop appears entirely independent of that tendency on another. LEAF SPOT AND LEAF STRIPE DISEASES Besides the common and conspicuous diseases just discussed, there is in Illinois at least one disease of each of the cereals, excepting corn, which attacks its host by entering the leaves, damaging the plants, and reducing yields by killing parts of the leaves. Barley is subject to a leaf stripe which: not only results in a reduction in the amount of leaf but also generally kills the stem it attacks. Wheat is affected by “speckled” leaf blotch, which shows first as small spots but later kills large parts of the leaf. Rye is subject to a leaf spot much like the wheat leaf spot, but its occurrence in Illinois is very rare. BARLEY STRIPE Caused by Helminthosporium gramineum Rabh. Stripe prevalence and stripe destructiveness are practically equivalent, for diseased stems die early, rarely maturing any grain. In obtaining data for this disease it is necessary, therefore, only to determine preva- lence. No data were taken in 1922 and 1923; but the lack of data from the many fields examined during these years should not be construed as showing the disease to have been absent. In the summer of 1924 data were taken from 43 fields containing 683 acres. They were distributed among the 21 counties included in the black area of Figure 73 and, as samples of the 215,275 acres of bar- ley grown in the area shown, were directly representative of 95.7 per cent of the State’s acreage. The records for 1925 were taken from five fields only, one in each of the five counties shown on Figure 74. Though containing a total. of only 80 acres, they were representative of 56,320 acres of barley—46.2 per cent of the State’s acreage. In 1926 data were taken from 6 fields located in the 6 counties shown in Figure 75. These fields, which contained 120 acres, were located mainly in the northeast corner of the state, in a region devoted to barley production, and may be considered as typifying the prevalence of stripe infection. 62 InLtinois NaturAL History Survey BuLLETIN L bE He = Ficre. 73-75. SOURCES OF BARLEY STRIPE DATA, 1924-1926 The black areas on these maps show the regions from which data were taken by direct examination of barley fields in each year. No data were taken in 1922 and 19238, but the fields examined in 1924 were representative of 95 per cent, and in 1925 of 46 per cent of the State’s acreage (see page 61). DISEASES OF GRAIN Crops, 1922-1926 63 The data accumulated show, when subjected to analysis, the follow- ing degrees of prevalence and destructiveness. | | Prevalence and Destructiveness: Calculated per- centages of stripe-infected barley culms Acreage Year examined | | For the acreage For the county For the | examined | acreage represented | State’s acreage | | | PLC vie ol ao 1924 | 683 1.69 | 1.90 1.76 1925 | 80 4.49 | 4.21 4.16 1926 | 120 2.25 | = “ | | | alerele | | | a The indexes in this table are representative of stripe infection, ex- cept that the index for 1926 is somewhat low, being unduly lowered through the influence exerted in the calculations by a large field of 40 acres in Macon County. Were statistics available for 1926, this index would approximate 3.37 per cent in the two columns now vacant. This figure will be used in the summary to be made later. SPECKLED LEAF Spot OF WHEAT Caused by Septoria tritici Desm. Wheat plants are killed by the leaf spot only in rare instances ; but in almost every season the disease is sufficiently abundant to cause serious damage to growing and maturing plants. Its prevalence is measured in terms of the number of stalks bearing spotted leaves; but since the spotting on the leaves varies in quantity, leaf by leaf and plant by plant, a special scale for determining destructiveness has been devised, a re- duced replica of which is shown in Figure 76. Such diagrams representing wheat leaves present, in a graded series, readily distinguishable degrees of leaf spot injury. Abundance of leaf spot infection, though in some measure correlated with the amount of injury, is not often the same, a fact explained through the ability of a spot located on the lower part of a leaf to cause the death of a large amount of leaf tissue extending upward beyond it. The examples in the scale indicate distinguishable degrees of injury as percentages of leaf area de- stroyed. They are also typical of types of injury commonly encountered in the field. In making use of the device, the observer collects a generous leaf sample at random, while he is making prevalence counts. As the sample will contain leaves with no infection, with light infections, and with heavy infections, it should represent the average amount of leaf injury present on disease-bearing stalks. Either then, or later in the laboratory, the parts of the sample—fresh in the field, but pressed and dried in the laboratory—are compared individually with the standardized diagrams by fitting each part between the two standards which it most closely resem- bles. The intermediate value of the sample part is not determined, for 64 Ittinors NAturRAL History Survey BuLLETIN to do so involves personal judgment to an extent certain to result in gross error. Instead, each part of the sample is considered as falling in the class represented by the scale diagram having the lower value of the two between which it falls. A record is made on the field data sheet of the number of parts of the sample falling in each class, and the average amount of leaf spot injury shown by the sample is determined in the manner described on page 19. An analysis of the data on prevalence and destructiveness then is made in the manner described in the first part of this paper (see pages 8-14). 2Ok 56% F¢S5% 56% 622% I#B Fic. 76. STANDARD FOR MEASURING THE DESTRUCTIVENESS OF THE SPECKLED LEAF SPOT OF WHEAT The black areas on each diagrammatic leaf represent the tissue killed by the leaf spot fungus. The area of the black spots has been measured and is given as a percentage of the entire leaf area for each diagram. Random samples taken in each field are compared with this scale, and the destructiveness of the disease is computed in terms of leaf area destroyed (see page 63). DISEASES OF GRAIN Crops, 1922-1926 65 Fic. 77 1923 Fic. 78 1924 Fic. 79 1926 Figs. 77-79. SouURCES OF THE DATA FOR THE SPECKLED LEAF SPOT OF WHEAT IN 1923, 1924, anp 1926 The black areas on these maps show the regions from which data were taken by direct examination of wheat fields in each year. During the period 1922-1926 fields containing a total of 12,787 acres were examined for this dis- ease, 862 acres showing none of it in 1922 and 3,225 acres having only a trace in 1925. 66 Itt1no1is NATuRAL History Survey BuLLeTIN Due in a large measure, perhaps, to the exceedingly heavy attack of leaf rust in 1922, leaf spot appeared practically absent from wheat fields. No positive data on its prevalence were secured that year. In 1923, however, a considerable quantity was obtained from 41 fields located in the 24 counties shown in Figure 77. The fields examined contained 2,428 acres and were representative of 40.3 per cent the State’s wheat acreage. The season of 1924 furnished the largest accumulation of leaf spot data of any of the seasons covered by the survey. Examinations were made in 149 fields distributed in somewhat varying numbers among 53 counties. They furnished a representative sampling of leaf spot preva- lence and intensity for the region shown in black in Figure 78. The fields themselves contained 5,667 acres, while the region which they represent grew 1,389,975 acres—60.3 per cent of the State’s 2,307,000 acres of wheat. Speckled leaf spot was rare in 1925. In 3,225 acres examined, only four instances of infection were found, one each in Clark, Crawford, Pulaski, and St. Clair counties. Though sufficient to give samples for laboratory diagnosis, they were so light that they could not be estimated, either in prevalence or severity. The infection for 1925 is to be con- sidered, therefore, as only a trace. In 1926, leaf spot was prevalent in fields throughout the central and southern parts of the state, but was not found in the northern third. Rec- ords of prevalence and severity were taken from 23 fields, which contained 605 acres and were located in the 14 counties shown in Figure 79. The data obtained were representative only of the infection in the southern half of the state, and the prevalence and intensity of the attack, expressed respectively by indexes of 11.0 and .39 calculated from these data, will be reduced considerably when 1926 acreage statistics become available for further calculations. The fluctuations in prevalence and intensity of attack, as shown by the field data when subjected to analysis, are as follows: | | Prevalence: Calculated per- | Destructiveness: Caleulated |}centage of wheat stalks with | Percentage of wheat leaf area diseased leaves | destroyed ay | Acreage | | ene Year examined | | For the | For the = | For the county For the | For the county For the | acreage | acreage | State's acreage acreage State’s | examined | repre- | acreage examined repre- acreage | | sented | | sented* rane oe x zi ca a. 1922 0 0 0 0 | 0 | 0 1923 2 88.7 88.3 89.2 26.2 | 23.2 21.8 Le | | 58.3 | ban 2 | 54.2 9.06 8.03 9.5 925. | | al T | “an ay 1926 | | ae -30 a | 2 | | | DISEASES OF GRAIN Crops, 1922-1926 67 Oats HALo BLIGHT Caused by Pseudomonas coronafaciens (Elliott) Stev. Though the symptoms presented by the halo blight of oats are quite different from those shown by the leaf spot of wheat discussed above, the method of estimating its destructiveness is much the same. Its preva- lence is determined, of course, as the percentage ratio of disease-bearing stalks. For estimating the intensity of the attack, a special scale, shown with considerable reduction in Figure 80, has been devised. The effect produced by halo blight in destroying leaf tissue appears to be consider- ably less than the similar effect of the wheat leaf spot. The degrees of destructiveness are more readily distinguishable, which permits the use SR 70% 90% Fic. 80. STANDARD FOR MEASURING THE DESTRUCTIVENESS OF OATS HALO BLIGHT The black spots on each diagrammatic leaf represent the tissue killed by the halo blight bacterium. The area of the spots has been measured and is given as a percentage of the entire leaf area for each diagram. Random sam- ples taken in each field are compared with this scale, and the destructiveness of the disease is computed in terms of leaf area destroyed (see page 69). of a larger number of individual standards in the scale and results in a considerably greater degree of accuracy in the eStimates. Otherwise, the methods of obtaining field data are the same as those previously discussed. During 1922, with halo blight of oats as with several other cereal diseases, data were recorded exclusively in the northern half of the State. Definite records were taken in 5 fields which contained a total of 9% acres and were located in the 4 counties shown in Figure 81. Al- though their combined acreage is not impressively large, their wide 68 Ittrnois NATturAL History SurRvEY BULLETIN Fic. 81 1922 Fics. 81-84. Sources OF DATA ON THE HALO BLIGHT OF OATS, 1922 AND 1924-1926 The black areas on these maps show the regions from which data were secured by direct examination of oats fields in each year. Fields containing a total of 4,198 were examined for this disease during the period 1922-1926, the 1,306 acres seen in 1923 showing only a trace of infection. DISEASES OF GRAIN Crops, 1922-1926 69 separation together with the constancy of the data endows them with a certain degree of dependability. In 1923 only two records of halo blight were obtained. A small field of 5 acres in Macoupin County, examined June 20, yielded the informa- tion that 65 per cent of the stems bore leaves having an average of 50 per cent of their area destroyed. In another small field of 3 acres in Fayette County, examined June 12, 3 per cent of the stalks bore leaves having 17.5 per cent of their area destroyed. In view of these facts, the prevalence and destructiveness of halo blight in 1923 were too light to be estimated. In 1924 data were taken from 78 fields which contained a total of 1,291 acres. They were distributed among the 43 counties which make up the black areas of Figure 82. The oats grown in these areas, 1,906,500 acres, make up 43.5 per cent of the State’s acreage. Again in 1925 abundant data were obtained. The fields examined, 56 in number, contained 1,189 acres and represented the infection pre- vailing in the 31 counties shown in Figure 83. These counties contained 2,237,510 of the State’s 4,724,000 acres devoted to oats production. The data, therefore, apply directly to 47.4 per cent of the State’s acreage. Much less abundant in 1926 than in the two preceding seasons, halo blight was, nevertheless, widely prevalent. Records were taken in the 9 counties included in the black areas of Figure 84. Prevalence and destructiveness, as shown by data obtained by the survey, are given in the following table: Prevalence: Calculated per- Destructiveness: Calculated centage of oats culms bearing | percentages of oats leaf area blighted leaves destroyed by halo blight s Acreage | Year |examined For the | For the For the county For the For the county | For the acreage acreage | State's | acreage acreage State’s examined repre- acreage | examined repre- acreage sented sented | 1922 97 77.90 78.30 67.70 14.20 | 14.80 | 13.60 1923 1,306 At | ait an im | uy | T 1924 1,291 61.33 46.45 47.87 8.27 8.27 | 7.30 1925 1,189 47.06 | 47.62 44.59 EGS YW dike | 5.76 1926 315 3.00 | A toGet AN a Sag cco rn [yeaa = I Bale eemia | | Summary of leaf spot and stripe data The variations in prevalence indicated for the individual diseases in the foregoing tables are brought into graphical comparison in Figure 85, while the differences in destructiveness are shown in Figure 86, So far as available data show, the trends of both prevalence and de- structiveness are the same for each disease; but there are marked differ- ences in these trends for the different diseases. In 1922, both in preva- lence and destructiveness, halo blight of oats stood high, while the speckled leaf spot of wheat was very low. In the succeeding year, 70 ILLINOIS NATURAL History SURVEY BULLETIN Prevalence Index S > S Destructiveness /ndex Fic. 86. DESTRUCTIVENESS OF THE LEAF SPOT AND STRIPE DISEASES, 1922-1926 DISEASES OF GRAIN Crops, 1922-1926 71 1923, their positions were reversed, the former being low and the latter very high. The summer of 1924 was marked by a sharp decline of speckled leaf spot and a sharp rise of halo blight, the two being very nearly equal in prevalence and in destructiveness. In 1925 both diseases stood below their marks of the previous years, but the decline of halo blight was slight and that of leaf spot great, leaving the former still serious and the latter insignificant. In contrast to these two, there was a slight rise in the prevalence of barley stripe. Finally, in 1926, halo blight and barley stripe exhibited declines in both prevalence and destructiveness, which contrasted sharply with the increase shown by the speckled leaf spot of wheat. SUMMARY OF ALL DATA SHOWING PREVALENCE AND DESTRUCTIVENESS All of the diseases considered in the previous pages have been of a kind which attacks and destroys above-ground parts of the plant. When considered in relation to their effects, they are of three types: destroy- ers of stem tissue, of leaf tissue, and of heads. One only, the smut of maize, commonly attacks all parts of the plant. Data on at least one of each of these types of disease have been given for each of the cereal crops for nearly every one of the five seasons. In any season an individual plant of any of these crops may bear one, and is likely to bear two or even more, types of disease. This fact is not particularly significant with respect to the prevalence of the several diseases, but it is very important in determining the destructiveness resulting from disease attack. The prevalence indexes previously given for the several types of disease are brought together in the following tables in closer relation to the individual crops. For each crop, the indexes of the several dis- eases are added together to give an index of total prevalence for each year ; and averages are obtained for the entire priod of the survey. This gives a fairly exact comparison of the five seasons. Prevalence: Disease in 1922 in 1923 in 1924 in 1925 in 1926 Average : | i | eno | See Leaf rust | eS oat) | 0 68.30 52.60 97.24 | Stem rust 22.06 0 1 S00 14.90 | 57.80 | Loose smut 89 39 Pa al 70 | Oe al Bunt 1.20 | 50 4.03 | 1-43) |] 745. | Seab 2 43 82 =| 3.46 | 21220) *| 6.50 | Septoria 0 20 | 54.20 -} ty | TOONS if | ee ee lle fe (est | | | . Total 120.68 | 227.31 141.54 | 90.83 | 133.89 | 142.85 | | | On wheat, as shown in the first table, the total prevalence, as well as the prevalence of each disease, fluctuates from year to year. The season | 72 Ittinoris NaturaL History SurvEY BULLETIN of 1925 ranks lowest, 1922 next, then 1926 and 1924, and finally 1923 at the peak with a total prevalence of 227.31. The prevalence of oats diseases is given in the following table: Prevalence: Disease wel | in 1922 in1928 | in1924 in 1925 | in 1926 Average | a , Crown rust 67.00 | 83.10 64.3 27.00 | 70.40 62.36 Stem rust 56.90 0 45.5 21.60 85.50 41.90 Loose smut 5.62 3.08 5.2 3.49 3.40 4.58 Scab ay 1 15 0 0 .15 Halo blight 67.70 ya 47.87 44.50 3.00 32.63 : | Total 197.22 86.18 | 163.62 96.68 162.30 141.20 | | The average prevalence of disease for the survey period is 141.2, which, when compared with the index for wheat, 142.85, shows how similar in average prevalence the diseases of the two crops are. The variation in prevalence, season by season, is as evident as in the case of wheat diseases, and the differences in prevalence shown by the in- dividual diseases are also evident. The barley data, though in general much less abundant than those of wheat and oats, furnished indexes of prevalence which compare as follows: Prevalence: Disease 7 1 in 1922 | in 1923 in 1924 in 1925 in 1926 Average | = | | Leaf rust 25.0 106.0 100.0 34.6 76.10 67,14 Stem rust 45.5 0 8.0 ifs) il 100.00 32.92 Loose smut See 5.30 1.64 411 5.00 4.01 Scab ee tak eA ee 12.86 T T 4.29 Stripe oa an'| even ees 1.76 4.16 2.25 2.72 | | | | | | | | | Total 70.5 105.3 124.26 53. 97, 183.35 107.47 | The prevalence indexes of rye diseases, though computed like those for barley, from rather limited data, give the following comparison. Prevalence: Disease ] in 1922 | in1923 | in1924 | in 1925 | in 1926 Average | | | | Leaf rust S)8) cal 50 3 22.2 | 44.5 | alisy al 47.04 Stem rust 50.0 | 0 25.9 | 0 | 0 | 15.18 Scab T | “ay | TT | T | T “a | | | | | | | | | tg | Total 149.1 | 50.3 48.1 | 44.5 | uGyeal 62.22 ! | | DISEASES OF GRAIN Crops, 1922-1926 73 Although only three diseases are considered, instead of the five or six diseases of the crops just discussed, similar seasonal variations in prevalence are evident. For corn, the number of diseases treated is of necessity small, and the information secured concerning them, due to conditions imposed, has often been inadequate. Yet the indexes of prevalence obtained show the following comparisons : Prevalence: Disease l = aT in t922 | inJt923 | in 1924 in 1925 | in 1926 | Average a | Ehren y|| (Faas Tianna | | ee Rust 34.6 | 3.0 | 62.6 | 33) 3 11.4 28.98 Smut 5.33 | 11.56 | 4.33 3.16 | 2.9 | 5.46 | | | | | ir at | ary | Total 39.93 | 14.56 | | 14.3 | 34.44 | | | > a © w a i a In order to show clearly the fluctuations from season to season of the total infectiqns by the diseases discussed, the totals from the above tables are shown in Figure 87. The same lack of agreement is evident when the prevalence of the diseases attacking one crop is compared with those attacking another. Of the five years covered by our sur- vey, there is not one in which disease prevalence was uniformly either o v S v N N Ss \ v N Q S iS KR Fic. 87. TOTAL DISEASE PREVALENCE FOR EACH CROP, 1922-1926 There was not one year among the five in which disease prevalence was uniformly high or low on all the cereals, nor was prevalence constant in amount on even one crop throughout the period. 74 Ittinoris NAturAL History Survey BuLLETIN heavy or light on all of the five cereals. The closest approach to such a condition occurred in 1925, the total prevalence of disease in that year being, for each of the five crops, less than the year before. Begin- ning with the wide range of total prevalences displayed in the season of 1922, the trend was downward for rye, corn, and oats diseases, but upward for those of barley and wheat’ in 1923; down for wheat and rye diseases but up for those of oats, barley, and corn in 1924; down for the diseases of all five crops in 1925; and in 1926 down for corn and rye, but up to relatively high points for wheat, oats, and barley diseases. The average total prevalence over the period of years covered by the survey is remarkably characteristic for each of the five crops. This fact is illustrated in Figure 88, in which the five-year index averages given in the foregoing five tables are shown graphically. The high prev- alence of infection on wheat and oats is indicative of the fact that these crops suffer most from diseases of their above-ground parts. The Corn hye 14/2 Oaps Wher i 20 W 60 80 M720 0 Prevalence /ndex Fig. 88. AVERAGE DISEASE PREVALENCE FOR EACH CROP The indexes of prevalence given in the text for the diseases of each crop have been added and averaged in order to show the normal prevalence of dis- eases on each crop in Illinois. lesser prevalence shown for barley and rye result, in part at least, from the limited range of culture of the first crop and from the scattering cultivation accorded the latter. In the case of corn, however, the very low average prevalence may be considered as directly correlated with the relatively minor ranks held by smut and rust-among corn diseases. It is not possible to gain a clear-cut conception of the destructive- ness of diseases through the simple process of adding the indexes, as has been done for prevalence. The types of injury caused by the various DISEASES OF GRAIN Crops, 1922-1926 75 diseases are dissimilar and, therefore, require a more complicated treat- ment. © From the data previously given to show the comparative intensity of attack, those relating to wheat are selected and shown together in the following table: Destructiveness: 1922 1923 1924 | 1925 1926 Disease | 2 3) BP Felis Bel et Blog lop |e SOI peo Se | 5/2/38] 8/2) 8) 8/2/48] 2/2] 8] 2] 2/8 Paci leees Sees |e Se (rae ay Se eee a eran }elelol] ele] s].ele/slele/]3zlelels RS PSI Se JS WR WO a ta A a Bes a me ae | ae} a | age: Hh ea rpel ue fa ae ] | hal ] ] | Pemeriat shee tb0. 8). |2o 180-8). 0.\. GT. foe Tle ces Been inter) eee Stem rust |i7.8]....|.... ee eee BG | apd Beet Tar feel es lit PE alee TETGIE (Se 9a (RR al Se | TS Ue | ee ae -| .94 Bunt Shes [ero PURE) occ Pomel COE Y(t beer Fle .| 145 Scab Seve aera ME a eee The We ATM ace P ep Bi aea| airs Leaf spot as soe fae let Re 9.5]. ae eis eee | | | | Total ]17.8|50.3]2.09 soa a}2.89 -6/28.6|/4.75 fo Disease attack injures or kills parts of the wheat stem, leaf, or head, thereby interfering with the ability of the plant to produce grain. The degrees of disease severity shown by the totals in the above have more or less commensurate effects upon the ability of the wheat to yield in each year; but a real understanding of the total destructiveness in one year with that in another is not readily attained by examining the table. In order to gain a clearer picture of the meaning of the figures, one may imagine, first, a wheat stalk, unattacked by disease, with stature and proportions of leaf and spike such as those illustrated by the standard in Figure 89. The effect of disease attack upon such a stalk, through the injury it causes, would be to cut down the amount of stem, leaf, and spike in proportion to the severity of the attack, leaving only the healthy parts to produce the harvest. Yield from a diseased stalk might be expected to compare closely with the yield of a healthy stalk having the same proportions as those left healthy on the diseased stalk. The effect of disease attack may be appreciated, then, by imagining five wheat stalks, one for each of the years covered by our survey, reduced in the size of their parts, as shown in Figure 89, in the exact proportions (inso- far as they can be depicted) indicated by the figures in the foregoing table. 76 ILninois NATURAL History SuRVEY BULLETIN Standard 1925 1924 1925 1926 Fic. 89. DESTRUCTIVENESS OF WHEAT DISEASES, 1922-1926 The effect of disease attack upon the stems, leaves, and heads of wheat, as indicated by the indexes of destructiveness given in the text, is shown for each year of the period 1922-1926 in comparison with an average healthy stalk. Standard 1922 19235 1924 1925 1926 Fic. 90. DeESTRUCTIVENESS OF OATS DISEASES, 1922-1926 The effect of disease attack upon the stems, leaves, and panicles of oats, as indicated by the indexes of destructiveness given in the text, is shown in com- parison with an average healthy stalk. See the text on page 75 for further explanation. DISEASES OF GRAIN Crops, 1922-1926 77 The destructiveness of the diseases of oats, barley, and rye may be regarded in the same way as the diseases of wheat. A statement of their destructiveness may be made, consequently, by omitting summarizing tab- ulations like that given above for wheat diseases and using, in their stead, illustrations similar to Figure 89. In Figure 90, the total effect of disease attack on oats, as indi- cated by the indexes of destructiveness given in previous pages, is illustrated for each year in comparison with an undiseased stalk of aver- age proportions. The stature of the stalk is shown reduced 29 per cent by stem rust attack in 1922, not at all in 1923, 13.8 per cent in 1924, 4.5 per cent in 1925, and 42.7 per cent in 1926; the normal leaf complement is illustrated as being reduced 40.9 per cent by the com- bined attacks of crown rust and halo blight in 1922, 30.6 per cent in 1923, 19.2 per cent in 1924, 6.4 per cent in 1925, and 9.9 per cent in 1926; and the spikelets are depicted as reduced 5.62 per cent by scab and loose smut in 1922, 3.08 per cent in 1923, 5.95 per cent in 1924, 3.49 per cent in 1925, and 3.4 per cent in 1926. The destructiveness indicated by the indexes given previously for barley diseases is shown in Figure 91. In comparison with a barley stalk Standard 1922 1925 1924 1925 1926 Fic. 91. DESTRUCTIVENESS OF BARLEY DISEASES, 1922-1926 The effect of disease attack upon the stems, leaves, and panicles of barley, as indicated by the indexes of destructiveness given in the text, is shown in comparison with an average healthy stalk. See the text on pages 75-77 for further explanation. 78 ItLinois NATurAL History Survey BULLETIN of normal proportions, stem rust is shown to have reduced the stature 12.4 per cent in 1922, not at all in 1923, .6 per cent in 1924, .2 per cent in 1925, and 28.7 per cent in 1926; the normal leaf complement is re- duced 5 per cent by the combined attacks of leaf rust and stripe in 1922, 5 per cent in 1923, 6.16 per cent in 1924, 9.16 per cent in 1925, and 9.25 per cent in 1926; and the heads are reduced 5.3 per cent by loose smut in 1923, 1.64 per cent in 1924, 4.11 per cent in 1925, and 5.0 per cent in 1926. The destructiveness effect of rye diseases is illustrated in Figure 92. In comparison with an undiseased stem of average proportions, the dia- gram illustrating the disease injury of 1922 has 25.5 per cent less stem and 55.1 per cent less foliage; for 1923 the stem is normal and the foliage 8.2 per cent smaller for 1924 the amount of stem of 13.9 per cent less, and the foliage 2 per cent less; for 1925 the stem is normal, the foliage .9 per cent less; and for 1926 the stem is normal but the foliage is 19.1 per cent less. In every season, the heads are drawn at normal size, as the data accumulated for head smut, scab and ergot showed no appreci- able general reductions from their attack. No similar depiction can be given of the effect of smut and rust on corn, for no satisfactory method of estimating their destructiveness has been devised. Standard 1923 1924 1925 1926 Fie. 92. DESTRUCTIVENESS OF RYE DISEASES, 1922-1926 The effect of disease attack upon the stems, leaves, and panicles of rye, as indicated by the indexes of destructiveness given in the text, is shown in com- parison with an average healthy stalk. DISEASES OF GRAIN Crops, 1922-1926 79 SOME RELATIONS OF DISEASE TO WEATHER AND CLIMATE There is abundant evidence in the experience of the farmer and the disease specialist that a vital relation exists between the occurrence of disease epidemics such as those described in the preceding pages and the accompanying weather conditions. Particular combinations of tempera- ture and rainfall have been observed to accompany—even to condition— severe attacks, and the absence of them generally is attributed to a cor- responding absence of favorable weather. The climate of a region, also, appears to determine to a very large extent what the relative import- ance of particular diseases shall be, or whether any disease shall be important. In the main, these interrelations have not been defined. With respect to weather, they have been generalized into the four categories, hot and wet, hot and dry, cold and wet, and cold and dry, each combina- tion being reported to have a particular influence over particular diseases. Since they refer, almost without exception, to departures from the aver- age conditions of localities or limited regions familiar to the observers who make the statements, it is not surprising that a list of their reported effects contain incongruous diversities of opinions, among which the only apparent agreement often is that weather has had a dominating influence. This applies particularly to diseases which attack plants above the ground ; for a number of diseases that are soil borne or attack the parts of plants that are in the soil have been subjected to extensive investigation in the laboratories of the Wisconsin Agricultural Experiment Station*, where many of their relations to temperature and soil moisture have been as- certained. But, with diseases attacking as well as spreading to and from aerial plant parts, the conditions which govern infection are chiefly those of the atmosphere, though it must be recognized that concurrent soil conditions may so hasten or delay the plant’s growth that even un- der ideal atmospheric conditions heavy infection does not occur. The difficulties which attend the artificial duplication of out-of- door weather in the limited space of a laboratory demand that the main facts of the disease-and-weather relation shall be determined by obsery- ing the two as they occur naturally. The conclusions arrived at may be subjected later to experimental verification and refinement; but the principles worthy of practical application to the problems of the farm certainly will be those derived by observing natural phenomena. It is not within the scope of this paper to define exactly any of these principles, for the chief intention has been to describe ways of measuring disease phenomena; but a small contribution may be ‘made by showing some of the ways in which disease data may be correlated * Jones, L. R., James Johnson, and James G. Dickson. Wisconsin studies upon the relation of soil temperature to plant disease. Wis. Agr. Exp. Sta. Research Bull. 71. 1926. 80 ILLINOIS NATURAL HISTORY SURVEY EULLZT:N with weather. As this material is presented mainly by way of example, it will be limited to the leaf rust of wheat, leaving the fuller treatment of it and other diseases to later papers. RELATION TO MEAN ANNUAL TEMPERATURE AND TOTAL ANNUAL RAINFALL The yearly history of wheat leaf rust may be considered to extend from about the first of July to the end of the following June. During this time, there are various periods of rest and active growth, the sum of which is expressed in the degree both of prevalence and destructive- ness reached by the rust at harvest. There is, first, a period of meagre existence in shocks, on stubble, in straw stacks, and on volunteer plants. Following it there often is a short period of very rapid multiplication upon the young, fall-sown wheat, which is terminated by the arrival of the winter months with their low temperatures. Finally, there is the spring and early summer, when the rust that was overwintered, aided by an accretion of wind-blown infection from the south, develops with exceeding swiftness, step by step with the wheat, to harvest. The success with which the rust-producing organism passes these various periods is determined by many factors, including temperature, rainfall, humidity, wind, and light, each of which is changing continually and independently. While varying greatly in individual seasons, the most important of these factors—temperature and rainfall—vary remark- ably little, as a rule, from year to year. The normal yearly mean tem- perature for Illinois, according to weather records extending back to 1878, is 52°, and the average yearly rainfall is 36.42 inches. During the years covered by the disease survey reported here (1922-1926), the mean temperature of a year has never been more than 2.3° above nor more than 1.4° below the normal mean, and the rainfall of a year has never been more than 1.57 inches above nor more than 3.59 inches below the normal total. Striking correlations ought to exist, therefore, between very small annual departures and the large annual variations in rust attack. The indexes of wheat leaf rust are given in comparison with the mean tem- perature and total rainfall for each rust year, that is for the period July through June rather than January through December, in the fol- lowing table: Rea | Prevalence ‘Destructive-| Mean temperature of} Total rainfall of index | ness index | the rust years the rust years 1922 94.1 50.3 | 54.8 | 41.73 1923 89.7 31.3 53.1 32.69 1924 68.3 19.1 | 51.9 38.74 1925 52.6 ileal 53.0 31.15 1926 57.2 11.2 51.3 35.15 DISEASES OF GRAIN Crops, 1922-1926 81 No complete parallels exist between either phase of the rust at- tack and mean temperature or total rainfall for year-long periods, but they are observable when temperature and rainfall are considered to- gether. In 1922, when the rust indexes were highest, both mean tem- perature and total rainfall were highest; while in 1923 the rust indexes, the mean temperature, and the total rainfall were distinctly lower. The destructiveness index was greater in 1925 than in 1926, and the combina- tions of mean temperature and total rainfall for these two years stood in the same relation. These facts, and the deductions to be drawn from them, are shown more clearly by diagram in Figure 93. The horizontal scale represents inches of total annual rainfall; the vertical scale, degrees of mean annual temperature. The heavily-lined axes are drawn from the points of aver- age mean annual temperature and average total annual rainfall for Illinois. The points labeled A, B, C, D, and E are the combinations of temperature and rainfall listed in the preceding table for the consecutive years 1922-1926. In the upper half of the diagram, a trend of rust increase from points B and D to point A is indicated by a dotted line; and in the lower half a similar trend is indicated by the dotted line drawn through points E and C. These two lines are nearly parallel, Rartall ip inches 30 35 45 Fic. 93. RELATION OF COMBINATIONS OF MEAN ANNUAL TEMPERATURE AND TOTAL ANNUAL RAINFALL TO DESTRUCTIVENESS OF THE LEAF RUST OF WHEAT The hyperbolic lines, drawn as explained in the text, pass through all the combinations of mean annual temperature and total annual rainfall capable of producing rust attacks with destructiveness indexes of 17.1 and 31.3, When enough data have been obtained, hyperbolas can be determined for every degree of rust attack, and the facts so learned can be used in predicting the intensity of attack in a given season. 82 IrLinotis NATURAL History Survey BULLETIN running upward at an angle very close to 45°. The trends which they indicate suggest strongly that rust destructiveness increases when both the mean annual temperature and the total annual rainfall increase. Although these lines are determined by a very small number of points, the fact that they run upward at an angle so close to 45° is strongly indicative of a certainty of correlation between increasingly heavy rust attacks and combinations of increasingly high mean annual temperatures and totals of annual rainfall. If it is assumed that this correlation is perfect, the line F-G may be drawn at a 45° angle through the intersection of the temperature and rainfall axes. Starting at the lower end, it should pass through points representing combinations of temperature and rainfall which would result in rust attacks with indexes rising steadily from 0 to 100. Certain of the indexes theoretically included in this line are shown, however, actually to have been produced by temperature-rainfall combina- tions not crossed by the line, thus suggesting that rust attacks measured by a given index may result from an infinite number of such combina- tions. To determine them exactly requires data for a period of years much greater than is now available; but a method for determining them approximately is suggested in the following: Point D is so situated that a line drawn from it to the intersection of the axes stands nearly at a right angle to the line F-G and, when continued, cuts the dotted line E-C at H. The point H hes about at the place between E and C where an index of 17.1 would be expected from in- spection, and it may be given that value. By rotating either point D or point H about the intersection of the axes in conformity with the known values indicated by points already placed, a hyperbolic line may be drawn through the points D, K,,and H, which theoretically runs through all the possible combinations of temperature and rainfall resulting in a rust attack having an index of 17.1. A line drawn from point B to the axis intersection departs at an angle of 55° from the temperature axis. If a line is drawn from the in- tersection, departing from the line F-G at tre same anzle, to cross tne line E-C, it will determine the point L, to which may be assigned the in- dex of point B, 31.3. By rotating either point B or point L as directed above for D, the hyperbola L, M, B is obtained. which runs through all of the combinations of temperature and rainfall capable of producing a rust attack of the index 31.3. From so small a number of points, the proper location of the hyper- bolic lines can be only suggested; but with the accumulation of data year after year, it will be possible to determine them with great pre- cision for every magnitude of rust attack. Practically, the delineation of a set of hyperbolic bands for predetermined ranges of rust indexes will be more serviceable than hyperbolic lines in predicting intensity of rust attack, for the absolute regularity of the line, which is determined DISEASES OF GRAIN Crops, 1922-1926 83 only by temperature-rainfall combinations, will be shattered by the oc- currence of varied atmospheric saturation deficits, light intensities, and other minor factors not readily subjected to quantitative measurement. RELATIONS OF DISEASE TO SEASONAL TEMPERATURE AND RAINFALL It has been pointed out that the leaf rust of wheat exists under quite diverse conditions during different periods of its year. Since these periods correspond to a certain extent, but not wholly, with the seasons of the year, it is necessary to visualize the points of difference and similitude among various years in order to determine the extent and characteristics of the rust seasons. Making use of diagrams constructed according to the method sug- gested by Taylor’, the mean temperature and total rainfall for each month of the years included in the survey may be so represented as to be com- pared easily, year with year and month with month. This is done in Figures 94-99, in which the vertical scale represents Fahrenheit degrees of mean monthly temperature and the horizontal scale, inches of total monthly rainfall. The combination of mean temperature and total rain- fall occurring in any month is shown by a point placed at the intersec- tion of the proper temperature and rainfall lines, and the month is desig- nated by an arabic numeral (1 = January, etc.). Figure 94 shows the progress of a “normal” year in Illinois, beginning with July and ending with the following June, the normal mean annual temperature and the normal total monthly rainfall for the state being indicated by the heavy, dotted lines. . Figures 95-99 are diagrams of “the years 1922-1926, in which, to facilitate comparison, the mean annual temperature and total monthly rainfall of a normal year are indicated as in Figure 94. These diagrams show that no one of the years with which we are dealing approaches a normal year very closely. The outstanding fact illustrated by all of them is that the rust year is divided roughly into halves, the first of which is characterized by falling, and the second by rising, temperatures. This we may take to be a characteristic of every rust year, to which we should attach only this very broad and obvious significance : From July through December the rust organism is being suibjected to increasingly rigorous temperatures and is decidedly on the down-grade, while from January through June the general upw ard trend of temperature has an increasingly favorable influence upon its rate of propagation. Lacking definite names, the terms “fall trend” and “spring trend” may be given to these periods. When a fall trend or a spring trend in any one of these years is com- pared by means of these diagrams with its counterpart in any other year, distinct differences are evident. Keeping in mind the variations in rust attack stated previously, the observable differences suggest at once that 1The settlement of tropical Australia. By G. Taylor in Geog. Rev. Vol. 8, pp. 84-115. 1918. 84 Intinors NaTurAL History Survey BuLLETIN F°| Rainfall iv inches \ F"\ Kairtall in inches 2 3 4 Ss Co 4 4 ZF J Ap Raintal/ in inches Ae Nae ae FN Fics. 94-99. TEMPERATURE-RAINFALL DIAGRAMS OF A NORMAL WHEAT LEAF RUST YEAR AND OF THE RUST YEARS 1922-1926 IN ILLINOIS The rust year begins with July, after the previous crop has been harvested, and extends through the following June. The trends of temperature and rain- fall, given as monthly means and totals, respectively, are shown for a normal year and for each year for which rust data were procured. These diagrams show that each rust year consists of two parts, the first of which has falling, DISEASES OF GRAIN Crops, 1922-1926 85 rust abundance is related to the mean temperature of the fall trend and the total rainfall of the spring trend rather than to the rainfall of the fall trend and the temperature of the spring trend or combinations of the two. The following table emphasizes these points. Mean temperature Total rainfall See Destructive- Year ness index Fall trend | Spring trend Fall trend Spring trend 50.3 49.3 es 47.0 | 19.1 44.9 17.1 49.9 11.2 16.4 No parallel can be found between the variations in rust destructive- ness and either the spring temperatures or the amounts of fall rain given in this table, or between combinations of the two, whether the years be taken successively or grouped according to high and low rust indexes. Variation in the mean temperature of the fall trends and in the total rainfall of the spring trends, however, follows very closely the rise and fall of the rust indexes. How closely they follow one another is shown better by Figure 100. 7020 530 90 50 54° 56° Sa" OO" 5” to” 15" Destructiveness Index | Mean Temperature Total Rainfall duly- December danuary - June Fic. 100. COMPARISON OF RUST INTENSITY WITH JULY—DECEMBER TEMPERATURE AND JANUARY-JUNE RAINFALL, 1922-1926 and the second rising, temperatures (see page 83). The rust year may be divided also into three parts: an autumnal season, July-September; an hiber- nal season, October—March; and a vernal season, April-June (see page 83). 86 Intinois Naturat History Survey BuLLetTin Practically, we are lead to believe that, whenever a fall trend has rain exceeding 15 inches in amount, abundant rust is probable the follow- ing spring, if the mean temperature of the fall is 59°F. or more; but if the temperature is around 56°, light rust is to be expected. A spring trend with a mean temperature of 45° or more may be expected to be productive of a heavy rust epidemic when it follows a fall trend of 59°, if its rainfall is in excess of 17.5 inches, and of a light rust attack when it follows a fall period of 56°, if its rainfall is less than 16.2 inches. Records of the weather in Illinois are available since 1878, making it possible to estimate the frequency with which years favorable and unfavorable to leaf rust may be expected to occur in the future, on the basis of their occurrence during the past 48 years. Favorable, intermed- iate, and unfavorable fall and spring trends, alone and in various com- binations, have occurred the number of times shown in the following table: 5 é 4 N . i Combinations of temperature and rainfall, ties oe eine classified with respect to rust development ari RT ies é | in 48 years occurrence Fall trend alone PAW OG DD le e.U ss. cspeacs hiebatncols pl ttt eusecieftnevennye milsus caesar 7 f femme Gia WEL sxe paren taba siete ensue haus chanurre tauren over ate oatete rai?— nee 23 1/1.086 WabAMeAWKY 55 Gtieehanid anata co oon anaoe oad at 18 Spring trend alone rife TyiCoyre IG Sian er cd tedls o Ginrp op bs aang ay Diko ceo oemig Ot aemenoln 32 1/1.500 aN ole aglem(XoKENH Sy Mr aM Bhs ria Noho Go-cRMANhG ne eo ean OBES Oo 6 1/8.000 TINH OEU DIG Sacre ster savttepel see ner oa seer eae ohana eye Ue encan ens 10 1/4.800 Both fall and spring trends fa V OLAV ace seer tee) eit ea anat Te erRP yey ter ee pee 4 1/12.000 haley bg akere NKeM oon” Weed lel le Pech ort Oncnc AA cick aan: GeO Ocha Botun 3 1/16.000 unfavorable ....... Bin oshats coco coe son Hone a 6 1/8.000 Fall trend favorable Springyatrend wantermlediart circa) karst iieieUslsiete meets « 0 0/48 .000 spring: trend unfavorable... ............:0..+6. | 3 1/16.000 Fall trend intermediate Spring? trem farvioralbll ery. wey wi nte ein «+ ekstenseateecs aterahass 19 1/2.526 Springs. trend mPa voraoleye acts ss les tereiai=t= mG erat © 1 1/48.000 Fall trend unfavorable Sjopmuokers jnasvaGl pniziivord-Noll aos bang oeerdhs Goda Otero 9 1/5.333 spring trend intermediate................... A 3 1/16.000 Stated more concretely, the expectation with respect to any fall is only 1 in 7 that it will be favorable to rust, nearly 1 to 1 (even chances) that it will be intermediate, and only 3 in 8 that it will be unfavorable; and with respect to any spring the chances are 2 in & that it will be favorable, 1 in 8 that it will be intermediate, and 1 in 4 that it will be unfavorable. The probability of a favorable spring following a favor- able fall is only 1 in 12, and of an unfavorable spring following an unfavorable fall only 1 in 8; but the likelihood of intermediate falls and DISEASES OF GRAIN Crops, 1922-1926 87 springs cccurring together is approximately 4 in 5. Stated in terms of leaf rust attack, it is probable that on an average only one year in twelve will be productive of a severe epidemic and only one year in eight of a very light epidemic, while four years in every five should have moderate rust attacks. This statement, however, should not be expected to apply rigidly to any small number of years; it is significant only for a period of half a century or more. Referring again to Figures 94-99, three divisions of the year may be distinguished, including first the months July, August, and September, next the months October through March, and finally the months April, May, and June. For convenience, these periods may be designated re- spectively as aestival, hibernal, and vernal, these terms applying not only to periods of the year but also to distinct phases in the rust otganism’s history. The mean temperatures and total precipitation of each of these periods for the years during which rust observations were made are com- pared in the following table, with the indexes of rust destructiveness. | Aestival period Hibernal period Vernal period : Destruc- | A Year tiveness | Mean | Total pre- Mean Total pre- Mean Total pre- index | tem- | cipitation | tem- cipitation | tem- cipitation | perature | ininches (perature! ininches perature in inches reir ye | eae ] i j 1922 | 50.3 | as | 13. 39)./0° 18.02 Hom owaio” 2] 10.13 1923 | 31.3 | 4 | Tho |» cisely | llsyee ts) | Gl. 7) 10.27 1924 eeeLO Aste (omitted (eSTMD esas |eOese | al2e5s 1925 | alr (al | 3 | nl 39.38 | 10.50 | 64.2 | 9.08 1926 | alae sana 10. eae) 15.18 59.8 =| 9250 | | | | | The variations of the rust indexes is not corre!ated throughout the five years with either the temperature or precipitation of any season; but the heavy and light rust years, as groups, find striking counterparts in the heavy and light precipitations of their corresponding vernal seasons. It is evident, also, that the effect of precipitation in these seasons is intimate- ly related to that of temperature. The 15.18 inches of rainfall in the hibernal season and the 9.51 inches in the vernal season of the light rust year of 1926 approach very closely the corresponding amounts in the heavy rust year of 1923, but the expectation of heavy rust from this cause is counterbalanced by low mean temperatures in both seasons. An illustration of the opposite relation occurred in the light rust year of 1925, when the mean temperatures of both the hibernal and the vernal periods. which were almost as favorable as those of the heavy rust year of 1922, were offset by very low precipitation totals. The relative effects of various mean temperatures and totals of pre- cipitation upon the amount of rust infection could be determined by mak- ing numerous comparisons like the foregoing; but at the present stage of our inquiry the details in our possession are not sufficiently abundant 88 Ittinoris Natura History Survey BuLLetirn to furnish satisfactory conclusions. We might assume, for example, that the influences of temperature and rainfall are cumulative and that their total effect is expressed in the amount of rust eventually produced. On this basis, we could develop a linear equation for each year and, by comparing the equations, arrive at average effects to be assigned to each degree of mean temperature and each inch of rainfall for each of these seasons. Actual tests of this process with the data at hand have yielded results which, though very suggestive, are still too indefinite to be presented, ex- cept in generalizations. They suggest that there is a well defined mini- mum temperature below which rust infection can not occur, and that above this threshold the amount of rust produced increases more and more rapidly as the temperature increases. The months of May and June should be regarded as the most criti- cal of the year in the development of a leaf rust epidemic, for at this time the infections that have survived the rigors of the previous months begin to grow anew, producing new spores and starting the new epidemic. As the days pass, infection is increased not only from the local sources of spore supply but also by spores blown in on the wind from fields to the southward. Even under the most adverse circumstances, sufficient infec- tive material is present in the fields of this State to produce a very de- structive epidemic. Whether it remains mild, as it did in 1925 and 1926, or becomes serious, as in 1922, 1923, and 1924, depends very largely up- on the spring temperature and rainfall. A comparison of rust indexes and the weather of May and June is given below. | Veather conditions of May and June Destructiveness | Year index | | | | Mean temperature | Total rainfall 1 z ee aye ieea | ui 1922 | 50 3 | 70.2 | 5.08 1923 | 31.3 | 67.0 | 7.88 1924 | als yeuf | 63 4 | 10.35 1925 | UGhsit | 67.0 | 6.42 1926 | an) { 66.5 | 6.39 | | | It is evident that neither temperature alone nor rainfall alone in these months is related to heavy or light infections. The mean tempera- ture in 1925, the year of lightest rust, was the same as in 1923, when there was a rather heavy rust attack; and the rainfall of 1922, the year of heaviest rust, was less than in either of the two light rust years, 1925 and 1926. The degree of rust attack must be determined, consequently, by the condition produced by the mean temperature and total rainfall combined. It is not possible to see, in the foregoing table, what inter- relations such combinations may have, but if a diagram, as in Figure 101, is drawn and the different years properly plotted upon it, they may DISEASES OF GRAIN Crops, 1922-1926 89 be made clear. The normal mean temperature for the May-June period in Illinois, 67.1°, is shown by the heavy horizontal line, and the normal total rainfall, 8.08 inches, by the heavy vertical line. The point at which these lines cross represents the normal mean temperature and total rain- fall condition for the May-June period. The actual combinations for the years in question are shown on the diagram, circled dots marking years of heavy rust and circled crosses years of light rust. It is remarkable that the points representing heavy rust lie in a nearly straight, diagonal line running from the upper left to the lower right corner of the diagram, while those for light rust lie close together near the middle of the upper part of the cold, dry quarter. The number of seasons for which there are records are far too few to permit complete acceptance of the relations the diagram suggests; but in view of the principles underlying mathematical correlation, it is quite probable that the general trend, at least, of the May-June mean temperature-total rainfall combinations likely to produce heavy rust at- tacks is indicated. Rainfall in inches Ory Cold Fic. 101. CorreLatioN BETWEEN THE DESTRUCTIVENESS OF WHEAT LEAF RUST AND THE MEAN TEMPERATURE AND TOTAL RAINFALL OF THE MAY-JUNE PiRIOD Cire’es mark the May—June weather in years of destructive rvs: and circled crosses in years of light rust. The line connecting the circles suggests that, contrary to the usual opinion, dry, hot weather will produce the heaviest at- tacks. Damp, cool weather produces moderately serious disease, and rather dry weather with usual temperatures results in mild attacks. 90 Itinrnors NAturAL History Survey BuLierin The geographical occurrence of dates of first spring infection, and the temperature relations governing the uma development of an epidemic It has been said that there is always sufficient infective material pres- ent to produce a destructive epidemic if conditions are favorable, Al- though, as has just been shown, several distinguishable parts of the year, as well as the year as a whole, influence very definitely, the intensity of disease attack, the fact remains that each year’s epidemic is inde- pendent, in a measure, of all the seasons of the year except’ the spring, for then spores of the rust organism blown from distant places,by strong winds serve to introduce new infection. For this reason, it is worth while to inquire into the time when spring infection is likely to occur and the conditions under which various grades of intensity are developed. The earliest appearance of rust in Illinois, as shown by our Survey records, varies considerably according to locality. The late start on field work in 1922 failed to furnish any such records for that year, but'in the years 1923, eee and 1925 a number of dates of earliest infections were secured. In 1923, five such observations were made; in 1924, 8; and in 1925, 11: eee roughly from south to north, they are given by counties in the following table under the “observed date.” | Observed | Theoretical Observed | Theoretical County Date date County Date date 1923 1925 Bond June 5 Madison June 4 Coles | June 8 | June 7- 8 Greene June 4 | June 4- 5 Macon June 9 | June 9 Clark June 9 | June 8-9 LaSalle June 15 | June 14-15 Coles June 10 | June 9-10 Cook June 30 | June 18 Edgar June 10 | June 10-11 || Macon June 12 | June 9-10 1924 || Piatt June 11 | June 10-11 Calhoun June 6]| June 4- 5 Champaign | June 11 | June 11-12 Jersey June 6) June 4-5 || Logan June 12 | June 10-11 Macoupin June 4] June 4-6 || McLean June 13 | June 12-13 Champaign June 15 | June 14. | Iroquois June 19 | June 15-17 Moultrie | June 17 | June 11-12 || Piatt | June 17 | June 12 | Kankakee June 25 | June 18-19 || Will | June 25 | June 19-20 || | Upon inspection of this list, it is apparent that, though the dates for comparable localities differ year by year, the first rust infection is always earlier in the south than in the north and for, the same latitude, earlier in the west than in the east. This suggests that rust infection occurs in close conformity in the spring with Hopkins’ Bioclimatic Law', which 1 Hopkins, A. D. Periodical events and natural laws as guides to agricultural research and practice. U.S. Dept. Agr. Weather Bureau, Monthly Weather Review. Supplement 9, 1918. eS a DISEASES OF GRAIN Crops, 1922-1926 91 states, essentially, that ‘‘other conditions being equal, the variation in the time of occurrence of a given periodical event . . . is at the general aver- age rate of 4 days to each 1 degree of latitude, 5 degrees of longitude and 400 feet of altitude, later northward, eastward, and upward in the spring and early summer, and the reverse in late summer and autumn.’ In accordance with this view, the State of Illinois has been divided into the sections shown in Figure 102, which represent theoretical time variates of periodical events in harmony with adjacent states. The slant- ing longitudinal lines represent a difference of approximately four-fifths AN Fic. 102. THEORETICAL TIME-VARIATE LINES FOR ILLINOIS, ACCORDING TO HOPKIN’S BIocLIMATIC LAW The earliest wheat leaf rust infection occurs in the south, and at a given latitude infection occurs earlier in the west than in the east. The seasonal progress of infection is in the northeasterly direction taken by the longitudinal lines. The horizontal lines represent, from south to north, a difference of one day, and the longitudinal lines a difference of four-fifths of a day, from west to east, in the appearance of first rust infections. When the first infection is observed in the south, the date of its appearance in any more northern region can be predicted accurately. 92 Intinois Naturat History Survey BuLLETIN of a day, and the somewhat slanted horizontal lines a difference of ap- proximately one day in the occurrence of a given event. Selecting the first date given in the foregoing table for each year, it is possible to compute from Figure 102 a theoretical date of first in- fection for the other counties listed. As an example, in 1923 rust was first seen in Bond County June fifth, but it was not seen in Coles County until June eighth. Referring to Figure 102, it is readily determined that, by the provisions of the law just stated, rust should have appeared through the southern part of Coles County June seventh and through the northern part June eighth. There is a practical coincidence of ob- served date (June 8) and theoretical date (June 7 and 8). Theoretical dates so determined are given in the preceding table for each of the observed dates. A comparison of the observed and theoretical dates shows in all cases a very close agreement. The statement seems warranted that, when the appearance of rust has been observed in the southern part of the State, an accurate prediction can be made of the date on which initial infections will occur in any part further north. The dates of spring infection influence the total amount of disease subsequently produced. If they are early, there are longer periods of multiplication; but if they are late, the periods of multiplication are shorter. This, however, is probably much less important than the tem- perature and rainfall of the multiplication period, for it is commonly observed that low temperatures inhibit the development of infection, though prolonging somewhat the growing period of wheat, while high temperatures not only inhibit infection but greatly curtail the growing season of the crop and consequently the multiplication period of the dis- ease. As temperature appears to be the controlling factor, it is to be expected that certain average temperatures occurring through periods of given extent should result, other conditions being equal, in definite amounts of infection. These other conditions will not be equal, of course ; but when a large territory is included, the variations they cause should fluctuate about the general trend of the temperature effects. The amount of rust observed at a certain time in a certain field may be considered, therefore, to be in the main an expression, somewhat modified by other factors, of the effect of the temperatures accumulated from the time of the initial infection to the time of examination. A statement of the accumulated temperatures may be obtained by adding the daily mean temperatures recorded by the nearest Weather Bureau station. In the following table, these totals as well as the average mean daily temperature during rust development are given in connection with amounts of rust observed in 1926. It should be stated that the first infection was observed June 2 at Paris. From it, theoretical dates of first infection were determined, by the prediction method just described, for instances not definitely observed. —- DISEASES OF GRAIN Crops, 1922-1926 93 OBSERVED Rust INFECTIONS, COINCIDENTALLY ACCUMULATED TOTAL MEAN DAILY DEGREES, AND AVERAGE MEAN DatILy TEMPERATURES FROM FIRST INFECTION TO DATE OF EXAMINATION Aver- ; Aver- age | age mean || ec De- Mean daily || De- Mean yale | struc- daily | temper- | 5 | struc- | daily | temper- Re ee ces face [ae | | ness. |aceum: | tare s ac a uring | ss ) ace = ring index | ulated Het i index | ulated aurte devel- || | devel- opment | } opment | ks | 5 Boone 14.0 4,105.0°) 66.2 Macon 2.0 | _ 453.5°| 64.8 Champaign 33.6 2,051.5 70.7 Madison | 6.0 | 2,040.0 | 68.0 Champaign 20.0 2,209.5 (alae Marion trace’ | 2529-5) | o7228 Champaign 25.0 2,478.0 70.8 Marion | trace bis) n5: 71.6 Clark 10.0 1,019.5 67.9 Marion | 1.0 1,529.5 72.8 DeKalb 15.0 3,373.5 68.8 Marshall 30.0 3,589.0 70.3 DeKalb 10.0 2,934.5 68.2 McDonough | 35.0 3,379.0 1.8 Douglas 32.0 | 2,012.5 67.1 McHenry |) S150 SHS nso) 8.4 DuPage 11.0 3,149.0 68.4 | Menard 30.0 | 3,407.5 2.5 DuPage 17.0 3,512.0 67.5 Monroe trace | 1,007.5 Peg Edgar 32.0 2,055.5 70.8 || Morgan trace | $26.0 68.8 Edgar |. 32.0 2A. 70.5 Moultrie trace | Saye eel Effingham | 5.0 | 846.0 70.5 Moultrie 16.6 5 68.1 Fayette 6.2 | 544.5 68.1 Piatt 35.0 5 73.2 Grundy 16.0 | 3,758.0 | 70.9 Randolph 10.0 | 2 i5h | gges Iroquois ily et) 2,313.9 71.9 || Saline 17.0 SR Grrl Iroquois 17.0 PRS IB VRE, 71.9 Sangamon trace 25) }) on. 6) Kane 15.0 3,272.5 66.7 St. Clair trace | -b | W124 Kane 29.0 3,200.5 66.6 St. Clair ee 5 72.4 Lawrence 4.5 372.5 74.5 Schuyler 20.0 iT hp 6 ea! Livingston 30.0 3,653.0 70.0 Vermilion 25.0 sails wieleed Livingston 60.0 | 4,154.5 | 72.8 | | | | | | Upon examining this table, many wide discrepancies may be observed between the amounts of rust developed and the accompanying accumu- lated temperatures. For example, the dev aac of a 32 per cent in- fection in Edgar County required from 2,055° to 2,115°, while south- ward, in Saline County, a much greater Sos era 2,778°, was. re- quired for a 17 per cent infection; and northward, in McHenry County, 3,355° were required for a 15 per cent infection. In Edgar County, however, the average mean daily temperature was 70.5° to 70.8°, in Sa- line County it was 75.1°; and in McHenry County, 68.4°. This dines that, in the field, there is a certain mean daily temperature, apparently between 70° and 71°, which may be termed the optimum, at which the rust organism can develop and spread most rapidly, and that if the mean daily temperature for any considerable number of days either falls much below or greatly exceeds this optimum the dev elopment and spread of the rust will be correspondingly inhibited. The items in the preceding table fall into three groups, correspond- ing in the main to geographic sections of the state. In the south and in the north large accumulations of temperature are required for small per- centages of infection because the mean daily temperatures are in excess of and less than the optimum, respectively ; but through the central part 94 ILtinois NATURAL History SURVEY BULLETIN of the state mean daily temperatures are close to the optimum. For con- venience, these parts of the state may be designated as lying south of the line numbered 41 in Figure 102, between lines 41 and 43, and north of line 43. The relation between the rapidity of rust development and accumulated temperatures in these districts is illustrated in Figure 103. These differences in rapidity of rust development may be explained further, in view of their geographic locations, on the seasonal character- istics of the region in which they occur. Spring and summer come earlier and endure longer in the south. There, optimum temperatures for rust development may occur before the wheat can be infected readily and may be succeeded by temperatures above the optimum before the epi- demic has progressed appreciably. In the central section, optimum tem- peratures appear somewhat later and endure through much of the grow- ing season. Northward, unfavorably low temperatures, characteristic of N wy 8 Cy S S a % v s » 5 i ° Xx S © S) u ~ % v S 3ao 1000 7500 2000 2500 J000 35500 4000 Jotal accumulated mean day-degrees of Temperature Fig. 103. HErrecr oF TEMPERATURE UPON THE DEVELOPMENT OF A WHEAT LEAF RUST EPIDEMIC, FOLLOWING THE OCCURRENCE OF FIRST INFECTION The destructiveness indexes given in the table on page 93 are shown graphically here with their corresponding accumulations of mean daily degrees of temperature. They fall into the three rather distinct groups indicated by the three curved lines. The line of greatest rustiness is obtained from observa- tions made in central Illinois; the intermediate line, by observations in southern localities; and the line of least rustiness, in northern localities. es ee) Ee DISEASES OF GRAIN Crops, 1922-1926 95 the early growing season, are succeeded for a short period by optimum temperatures as the crop nears maturity, and immediately are followed by the high temperatures of summer. The curves shown in Figure 103 suggest that a more complete analy- sis (not possible with the data we now possess) would show that tem- peratures could be classed as effective or non-effective in the development of an epidemic and that exact values could be assigned, in terms of ve- locity of disease development, to effective temperatures, which would make it possible to predict with a high degree of accuracy the ultimate intensity of attack in any season. This problem, however, requires data much more extensive, detailed, and complete than have been obtained thus far. SUMMARY AND CONCLUSION With strikingly few exceptions, attempts made heretofore to esti- mate variations in disease attack have resulted, with respect to com- mercial crops, in statements so patently generalized, both as to prevalence and damage, as to be far from convincing. Based on inexact observa- tions and evaluated from memory or from too brief and inadequate notes, they have dealt too much with reductions in yield and money losses, neither of which can be estimated fairly with our present knowledge. While such estimates have been, as a rule, far too conservative, placing losses inordinately low, the fact remains that an abundant yield is de- termined chiefly by soil, weather, and proper cultivation. It is only in the exceptional season that yield is determined by disease attack alone. The methods for collecting data on disease outlined in the preceding pages take into account the effect of disease upon the individual plant and its parts rather than upon yield. Disease prevalence and disease destructiveness have been observed directly, in accordance with definite rules, in fields selected at random, in order that representative samples might be secured; statistical methods of a relatively simple nature have been devised and used in evaluating the data thus secured; and indexes have been computed which represent the disease attack as it actually occurred. Because they do not involve the necessity of comparing or evaluating indirectly estimated reductions in yield or money losses, these indexes furnish the most satisfactory means now available for comparing disease attacks, year with year, or region with region. They also provide a means of visualizing the effect of disease upon the crop subjected to attack, as was illustrated in Figures 89-92. The use that is to be made of exact data collected by studying and measuring epidemics under natural conditions has been exemplified, though briefly, with some of the wheat leaf rust data. It has been shown that there is a well defined relation between intensity of attack and annual mean temperatures and yearly totals of rainfall; that in the July-Decem- ber period of the year temperature has a greater influence than rainfall, 96 Intinois NAturAL History Survey BuLLEeTIn while in the January-June period rain is the more important, in determin- ing the destructiveness of a year’s rust attack; that there is a possibility of predicting with reasonable accuracy the date upon which the first spring infection will occur in any part of the State in any year; that dur- ing the months of May and June the correlation between disease develop- ment and weather conditions lies mainly with temperature; and that the degree of destructiveness which an epidemic, once started, is likely to attain may be predicted from the rapidity with which degrees of mean daily temperature accumulate. Such results as these outline only the broadest of the principles which underlie the yearly development of disease epidemics on the crops grown on the farms of Illinois. Although they have no immediate application to the problems of the farm, they are the general laws from which the rules of practice must be drawn. What has been learned in the case of wheat leaf rust must be learned also for the other diseases of wheat, and for the diseases of other crops; the laws pertaining to all must be refined by further observations and analyses; and the practical rules at last determined must be subjected to final tests, before the task is finished. . STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVIL BULLETIN Article II. A Manual of Woodlot Management BY Cc. J. TELFORD PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS November, 1927 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVII. BULLETIN Article II. A Manual of Woodlot Management BY C. J. TELFORD PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS November, 1927 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. SHELTON. Director BOARD OF NATURAL RESOURCES AND CONSERVATION A. M. SHELTON, Chairman WILLIAM TRELEASE, Biology Joun W. Atvorp. Engineering Henry C. Cowtes, Forestry Cuartes M. THompson, Representing Epson S. Bastin. Geology the President of the University of WitiiamM A. Noyes, Chemistry Illinois THE NATURAL HISTORY SURVEY DIVISION STEPHEN A. Forses, Chief ScHNEpP & BARNES, PRINTERS SPRINGFIELD, ILL. 1927 69643—3,000 CONTENTS PAGE SPRMPATRGCNTCL NEVI TAINED) “SURMMESIVELIY yoo acts che eS s}useie’ ais vais eye Siete o"= icv) cuaceis.c oe wie os Was pene 101 WTAE ASNT 11 CACHONNE see et syope kc Sin Bin. o ls i 0) 6. w iS Tesla! Ce eqe ops .cieyw Re eels se wis IS Be & ayanciene 103 TT ITS Pe a OT) ee es ae a nea eae hae 105 The woodlot as a source of fuelwood, posts, and lumber for the farm... 105 (Table I, Required renewals of untreated posts, p. 106) OOORDTIGS TRCEC DO ee Re See Se Ol GS DUNE DIC eae OS eee Oe ERR rao es 109 (SGN A Ang aig co Reno Sars ot ican ee aCe ra arate acne eee ae perso 109 Bere eRe een See Iett Seki Is) ayes dn ereiasrasioin she Soe Siw es splasneaneas 109 PMBGCISEANC TUNE OUSMGISCASES: | 2)/jwestsesd)s(e re a oyoieiah sieiareveys sbaecdes-s sve esia reson oie 110 Adaptation of trees to soil.............. Pea cinee so eee has Srapetel nce eee 111 (Tables II-VII, Average growth rates, pp. 112-117) (Table VIII, Lists of species recommended, pp. 118-122) BEA APE eS YSLCI TOLL SU VACHIL EEG sraic cis ina aie wiaie wail a inte) wleo\aie cin iain oa Setaiy fetes 123 Development of an even-ared stand: .. .. 2 swede eee tne seers cle 125 TERPS E) Sha ton AT OCT iis Goes A OS ke) SER Role ES Pe an 126 (Table IX, Average yields from even-aged stands, p. 127) FTES Te Tb ee rans eet teria arc ease mae Gass 9) oars nic sukrarsi ou win aya ue a 126 RESENSrANIONMICOO SPLOULS GTS oni s 5 ete ace'n cote oe oh ieee ae ee eet 126 TereneraiOon mieOMe SCCM emule piece ees meters ste yertaim cst vm yecit occa. ceie ticle Shiga ee we 141 (Table XI, Number of seeds to sow to secure 15 hardwood seedlings to the foot, p. 141) [itrrine. op ogOnen his She SI So ODO DRISIniC CPOROOIG DIES IO Cat acrcr scien Sear eae 143 Commercial aspects of reforesting cleared land...................... 143 Plantations) tor production. Of SAWw-lOZS is. 22. ~ ccm cece eee eee ae een 144 Growme Conilerous, planting’ -StOCK. i .): . sien c ces wee twee Meee 145 (Table XII, Number of seeds to sow to secure 100 conifer seedlings per square foot, p. 145) Terris TERETE” Se SO 56 © COIS OOS IC IEE IS OLE CEE epee Saecn 147 GENILEr MIANTATIONS (ONG SADOS ciao 15 . 152 (Table XIII, Yield per acre for fully-stocked cottonwood, p. 155) Period for most profitable, harvest ....0. «0. 22). os «ests Ree 156 Plantations for post production. 32)... fee +. © «.1) ole erci ele nee ... 156 Catalpa 2. sr ike saecd cue: 2 Pacatie eystyeye, tele ea a Sesie buss eect sel eoalc i 157 Blacks OCUSE 1 .¢2)s {ste Aisi sates waters sosiahader« Wi clis arses fies Garr 160 OSBZO OTANI ES i ois apecae siden cho feea cle & Mian Gost cues, Aleve wha ieee 162 Summary of points on seed and tree planting.................-ee000- . 163 Measuring and marketing woodlot products.............200c eee eeeteerecs 164 Choiceno£ PrOdUCts 521 WF ies oleh ce oavele donors Sieve isle 8s otal ade 164 (Table XIV, Shipping distances determined by the margin between average sale price and average manufacturing cost, p. 166) (Table XV, Net returns per acre as influenced by kind of product and shipping distance, p. 167) Sa WIGS Se eh OL SR alate cot dad ceca owas Abe eat eure eta 168 Histimating: ‘standing: “timbers: . - : t peer ee > 2 ~ ‘ae ‘ S - a hy at ss . . % ‘ s F ‘ . AFTER THRESHING COMES SAWMILLING VoLUME XVII. ARTICLE II. A MANUAL OF WOODLOT MANAGEMENT Cc. J. TELFORD This manual is addressed to those landowners who have woodlots or idle land. It is assumed that they appreciate the intangible benefits accruing from the woodlot as a refuge for wild life, as a local modifier of dry and cold winds, as a protection to the sources of local water supply, as a means of enhancing the beauty of the landscape, and as a place for recreation; and that they also appreciate the service to the nation rendered by productive forests. Our purpose is to define the true forest lands in Illinois, to outline the methods for the proper man- agement of the woodlot, and to give the general returns to be derived from the managed production of wood. The point of view throughout is the growing of a wood crop as a producer of revenue. The broad essentials of woodlot management are outlined briefly, the methods which are adapted to the growing of timber under different conditions of site and market are discussed at some length, and the methods of measuring and marketing the product are described in detail. SuMMARY OF GENERAL MEASURES IN THE MANAGEMENT or NatuRAL WoopLots The broad essentials of woodlot management may be summarized as follows: (1) Put the soil in condition to support the best growth by de- veloping and maintaining a good leaf mulch. Since fire, grazing, wind, and sunshine destroy this mulch, keep out fire by eternal vigilance, stock by fencing, wind by leaving a dense wall of bushes on the borders and small trees within the woods, and sunshine by growing enough trees to provide a complete shade. (2) Stock the area with the most rapidly growing species suited to the products in view. In Table VIII (page 118) are listed the species recommended for the specified products under definite soil conditions. Work out the worthless trees, such as decayed, broken-topped, crooked- or short-boled, very limby ones of all species, and all trees of those species classed as weed trees and listed on page 118. Observe the seed bed conditions which favor the seeding in of trees of the species desired— shade or sunlight, leaf litter, humus or mineral soil—and create such 102 InLinois NaturAL History Survey BULLETIN conditions at the time when the desired species promises to bear good seed crops. If suitable restocking can not be attained naturally, plant seeds or small trees where reenforcement is necessary. (3) Develop and maintain light conditions favoring the rapid growth of trees of good form, Enough trees should be grown so that tall clear-boled trees are produced. This type is secured when the trees during their early stages of development get direct sunlight only from overhead and none on the lower branches. This crowding, intended to force the tree to discard the lower limbs, must be done when the trees are young. The naturally pruned tree should be so developed as to show a tall straight stem, with the crown bunched at the top when it has attained a diameter of 6 to 10 inches and is passing the period of most rapid height growth. After this period, there will be progressively less stem added to the top from which branches can grow, and continued crowding cramps the crown. At this stage, therefore, thinnings should be initiated to supply space for lateral crown expansion. Such thinnings should be light, removing just enough live trees to give the select trees the space which they will fill up in five or six years. When crowding again occurs, another thinning is made. In even-aged stands, these thinnings can be done somewhat systematically at regular intervals. In an all-aged stand containing trees of different sizes, the process of regeneration, the crowding of immature trees to improve their form, thinnings to give additional space to the crowns of select trees, and cuttings incident to harvesting the crop, are carried on simul- taneously. Very frequently one operation can be carried out only by sacrificing some of the rules outlined. If a raw mineral soil is necessary for seedling regeneration, obviously the heavy leaf mulch can not be retained; if undesirable trees have usurped a large part of the area, these can not be removed without letting in sunlight; if the underbrush consists of weed trees, its removal gives access to the wind. In forest management, judgment rather than rules must be followed. A MANUAL OF WoopLoT MANAGEMENT 103 LAND CLASSIFICATION Land is classified according to its suitability for certain uses. The guiding principle usually is that lands should be put into the most pro- ductive group to which they lend themselves. Permanent classification is impossible—the swamp of yesterday, if drained, becomes productive cropland to-day, and may be the site of a town to-morrow—but at present almost nine-tenths of the area of Illinois is given over to the business of farming, so that a classification based upon the use of land for farming applies to practically all of the State. The farm owner generally classifies his land by answering two ques- tions: (1) Does the land lie so that cropping is possible? (2) Is the quality of the soil good enough to raise paying crops? Any part of the farm which seems unlikely to produce crops at a profit is leit in forest or is considered waste land. Some areas are undeveloped because they do not lie so that cropping is possible. The slopes may be too steep for tillage or they may be badly gullied. Similarly, rock-strewn fields discourage cultivation. Other areas are not farmed because the quality of the soil is not good enough to raise paying crops. This class in- cludes extremely compact hardpan soils, extremely loose sandy soils, worn-out cropiands, and soggy bottomlands. Some of this non-cropped land is potential cropland in the sense that by terracing, by draining, or by soil treatment it can be developed to produce crops, but there is no reason to believe that the economic conditions which have forced a decrease in the cropland area in Illinois during the past 15 years will improve enough to make profitable the immediate redemption of these marginal lands. The steep hillsides, gullied, rocky, or worn-out fields, sands, hardpan soils, swamps, and flood bottoms, it is generally agreed, should be in forests. From the viewpoint of the production of wood at a profit, this definition of the true forest lands is inaccurate. There are lands in the above list which can not produce any kind of wood crops at a profit, and there are certain lands now returning a profit in crops which would show a higher profit from forests. The farmer can not get a profitable wood crop from all lands too poor for general crops, nor does he need to confine his woodlot to areas unsuited to other crops. Considering, first, the lands listed above as unsuited to ordinary farm crops, we find that the revenue to be derived from either natural or planted forests on the hardpan soils (post oak flats) is less than the cost of management; that sands can usually produce acceptable timber crops only when planted to conifers; that the loams on steep slopes and on gullied, rocky, or worn-out fields usually prove acceptable for either native hardwoods or conifers; and that the floodlands are well suited to hardwoods. 104 ItLtinois NATURAL History SuRVEY BULLETIN Considering, next, the arable lands which are commonly considered as true croplands, we find that wood production is financially justifiable on such lands only when the sustained net returns from wood crops equal or exceed those from other crops which can be produced on them. There is very little conflict between wood crops and other farm crops on high-grade arable land. Aside from very limited areas: devoted to fence post or Christmas tree plantations, such land can not produce re- turns from wood crops comparable to those from the ordinary farm crops, and it should not be in woods. Low-grade arable land and unimproved pasture return net revenues comparable to those from pro- ductive forests. The net returns from the rough hillside pasture aver- ages about $1.25 per acre annually. The same kind of land in well- stocked hardwood forests yields a net return up to $1.60 per acre annually. Certainly, there is no economic justification for developing a pasture or low-grade cropland where woods are already well estab- lished and will give a better return, but, if they are once cleared, the very considerable cost of forest restoration more than offsets the higher revenue accruing from the forest. Keep such forested land in forest. The time has not yet come in Illinois when land already cleared, suit- able for and devoted to untilled pasture, will give sufficiently greater returns if restored to forest to justify the change; and such land, there- fore, should te kept in pasture. The detailed classification of farm land to determine the area of true forest land is most important and often difficult. Very steep hill- sides or frequently flooded bottomland can readily be classified as forest land, just as well-located, fertile prairie loams fall into the division of true arable soils. The need of information which can be used in classifying the marginal soils between these extremes becomes apparent in the survey of the farm. Should any of the improved lands be given over to forest? A proper system of accounting will show if the field in question is giving a net return. Lacking such records the classification becomes a matter of guesswork and is seriously liable to error. What slopes are too steep for cultivation? ‘The erosion of a given area is dependent upon the volume of water passing over it, the velocity which the water attains, and the character of the soil. The amount of water is influenced by the area drained and by the structure of the soil and soil cover, and the velocity is determined by the gradient. Heavy, compact clays absorb but little water and, when stripped of cover, readily wash at gradients as low as 6° in Hardin County. The open, ab- sorbent, deep loess soils in parts of Jackson County produce alfalfa on slopes greater than 20° without eroding; yet the open mixed sand and loess soils in parts of Whiteside County gully seriously when cleared. A MANUAL OF WoopLotT MANAGEMENT 105 These instances are advanced to show that no fixed ruling about de- gree of slope can be given*. If erosion has developed to such an ex- treme stage that gullies are forming, the land is true forest land; but areas may be in this class where erosion has not reached the gully phase. Actually less loss to farm soils results from gullying than from a general surface washing resulting in the steady removal of the surface soil particles, the consequent impoverishment of the soil, and the relegation of the area to the worn-out crop-land class. The effect on the soil of this surface washing is much more ruinous than is generally appre- ciated and reduces the fertility of soils to a greater degree than the demands of the crops for plant food. Thus arable slopes which do not gully may become true forest areas because they no longer produce profitable crops, and the classification is dependent upon crop records and costs. Torat AREA oF WoopLot Careful classification of the land on a given farm may show both wooded areas and cleared areas which should be forested. The total of these areas of true forest land naturally varies for individual farms. If the woodlot comprises all non-arable parts of the farm, it is evident that its size may bear little relation to the needs of the farm. The first aim in woodlot management, however, should be to supply the farm with those products which can be grown in the woodlot. In many 1n- stances the woodlots will also produce a surplus, and they must be man- aged with a view to marketing this surplus in the most profitable form. THE WOODLOT AS A SOURCE OF SUPPLY FOR THE FARM The wood consumed on farms in Illinois consists largely of fuelwood, posts, and lumber; it averages, as standing timber, 704.8 cubic feet per farm annually. The average rate of growth for fully-stocked stands is estimated at 41.1 cubic feet per acre annually, and the area of the woodlot required to supply this wood to an average farm is 17.1 acres. Considering these three major forms of wood used, the woodlot should in all cases supply the posts used on the farm; it should in most cases furnish the lumber; and it should supply the fuelwood only when this can be secured by utilizing tops and other materials which can serve no higher purpose. White oak fence posts cost on an average $0.24 each, and an average acre should pro- duce 38 posts annually, a total value of $9.12. The farm woodlot can usually supply all the rough lumber used on the farm. The operator will be dependent upon outside sources for the bulk of the surfaced lumber; for, although the woodlands of Illinois will produce crops of pine and other woods suitable for *For a discussion of erosion see Circular No. 290. ‘Saving Soil by Use of Mangum Terraces”, and Bulletin No. 207, ‘Washing of Soils and Methods of Prevention”, University of Illinois Agricultural College and Experiment Station. 106 I_tinois NarurAL History SuRVEY BULLETIN finished lumber, the process of manufacturing into siding, flooring, ceiling and similar finished products requires equipment not available to the woodlot owner. The fully-stocked average acre in Illinois should produce an average of 180 board feet of hardwoods annually, having a gross value of $8.10. The production of fuelwood as the chief crop is not an economical use of forests. To supply annually wood equivalent to one ton of coal requires nearly 2% acres of average woodland. With an average cost of coal of $6.60 per ton, the gross returns from such woodland devoted to cordwood are but $2.71 per acre annually. No greater mistake is commonly made than converting into eordwood the timber which is suitable for higher uses. The following information is given for the benefit of the woodlot owner who wishes to compute the woodlot area required to supply his farm. He may cal- culate from Table I the number of posts which will be needed annually to keep up his fences. TABLE I ReEQuiIRED RENEWALS OF UNTREATED Posts * Number of untreated : Number of untreated posts that must be | posts that must be Species | renewed annually | Species renewed annually ; in each 100 posts | in each 100 posts in fence | | in fence Osage orange .. 216 White oak ...... 10 Mulberry ...... 5 Sassafras ....... ial Black locust .... 5 1D bon aeoreehs aaa eee 16% Catalpa ..2...4.. 634 Black or red oak 20 Cedar ys: t)sebes 634 ASDA G sek attrne.s tact 20 Burr oak ....... 8 IWiaipLey Metra tiene cetone 2245 Post Oak ince ee 9 | Cottonwood .... 281% Walnut «223345 9 WT Olwe wee siete 28% | Each post is equivalent to 1.08 cubic feet in the standing tree. To get the total cubic feet required for posts, find from Table I the number required annually and multiply by 1.08. To get the total cubic feet required for rough lumber,divide the annual board feet requirements by 4.4. There will be approx- imately one cord of fuelwood in the tops for each 1000 B. F. of lumber taken out. If additional fuel wood is cut, the amount in cubic feet is found by multi- plying by 80 the number of additional cords required. The average annual growth in peeled stems for fully-stocked woodlots is as follows: A MANUAL oF WoopLot MANAGEMENT 107 Upland Cubic feet per acre HMI fin «3 Ssac5 eon dteuetee Seon Oconee pcos Debomeo Rone 15.8 Silky dhe 8 é5ong Gop eo saban Gnigae co aaeos Oompa copier 28.6 SEPT Rees Ciera fexaye CE Sie ys Ter wia luis) we wivic) oe vais waebe mele we cree 36.4 Bottomland BGakehickorys eli sashis ct. -e oe fehon e.cefesaeisieemaresies 45.0 Sycamore, soft maple, cottonwood, sweet gum, locust... 100.0 To find the approximate number of acres required to supply the farm, first find the total number of cubic feet required and then divide by the average annual growth per acre of the type in question. Example: Assume that the farm has 135 acres with a total of 844 posts. If the posts are white oak, there are required for renewals 10 posts for each 100 in service (Table I), or 85 posts yearly. Each post is equivalent to 1.08 cubic feet of standing timber, so that the annual drain on the woodlot for post material is 85 X 1.08, or 92 cubit feet. Assuming that the consumption of rough lumber on the farm is 1000 B.F. annually, and that there are 4.4 B.F. in each cubic foot of the standing tree, then the drain on the woodlot for lumber is 1,000 divided by 4.4 or 228 cubic feet. Assume that, in addition to the cord of fuelwood in the tops of the trees cut for sawlogs, there are cut 4 more cords per year. Each cord is equivalent to 80 cubic feet; hence, this drain for fuelwood equals 4 times 80, or 320 cubic feet. The total annual drain is then to be calculated thus: ADIN CDs Se ayes at ap c= 228 cubic feet Vit) ot Meeaeeepes Ae kare ae aes 320) Ve BOSS iat miteieraeterehate 52s se Ocal aarteracme Gl0he < If the woodlot is entirely on the hardpan soils, only fuel and posts can be 412 produced. To supply the 412 cubic feet needed for these, requires 5 OF 26.1 acres. 15.8 If the woodlot is on sands, the fuel, lumber, and post requirements of 640 640 28.6 ecubie feet can be supplied by = 22.4 acres. 640 Similarly, on the upland loams the requirements will be met by using 364 od. —17.6 acres; the oak, hickory, elm, ash bottomland type, by using 640 ___— 14.2 acres; the sycamore, soft maple, cottonwood, locust, sweet gum 640 type, by using —__= 6.4 acres. The gross value of the 1,000 B.F. of lumber, 100 5 cords of wood, and 85 posts is approximately $92, so that the woodlot on sand gives a gross return of $4.10 per acre annually, the upland loam type $5.23, the slow-growing bottomland type $6.48, the rapidly-growing bottomland type $14.38. oe i in are aie aia lil ILLINOIS NATURAL History SURVEY BULLETIN 108 NRE ie ae ; GRAZED WOoopLot. Young trees cleaned out, ground covered with turf. Natural replacement impossible. A MANUAL OF WoopLorT MANAGEMENT 109 WOODLOT PROTECTION The method of establishing and of harvesting a stand usually differ in even-aged and all-aged forests, but the same degree of protection must be given to each against grazing, fire, and attacks of insects and diseases. Grazing. The injury done to the Illinois woodlots by using them for pasture is greater than injury from all other sources. Throughout central and northern I[linois, woodland is not only being injured; it is being converted to cleared land by grazing. To appreciate the damage resulting from grazing, we must under- stand that grasses and trees are conflicting kinds of vegetation. A very slight agency in this region is able to upset the balance between them and determine whether a forest or a sod shall hold the contested site. The forest’s defenses against grass consist in shade and in a leaf mulch com- pletely covering the earth. This blanket of leaves and partly-decayed vegetable matter serves the very vital purpose of readily absorbing mois- ture and checking evaporation; in addition, it serves to cultivate and fer- tilize the ground, as it supports bacteria which are the agents for chemical reactions of the greatest importance in building up the soil fertility. The first effect of grazing is the injury to the small trees. A grazed woodlot is strikingly free from underbrush. More sunlight reaches the ground, and sunlight is as effective as fire in destroying the leaf mulch. Its destruction, coupled with the increased sunlight striking the forest floor, paves the way for the occupation of the site by grasses ; and the formation of a sod, in addition to effectively preventing tree seedlings from be- coming established, uses up the moisture. The effect of the very variable moisture conditions which result from the destruction of the mulch of humus and the compacting of the soil by the trampling of stock, is shown as the larger trees begin to die at the top and eventually drop out. First, the grazed woodlot becomes clear of underbrush, then grasses appear and a sod forms, the tops of the large trees die, eventually these trees drop out, and the area is cleared. If you wish to retain any area wooded, you must keep out live-stock. Grazing and wood production can not be prac- ticed on the same area except to the material disadvantage of each and the lessening of total returns received from the area. Fire. It is universally understood that fire is very destructive to our forests. The ordinary farm woodlot in Illinois is relatively small, usually isolated from extensive woodland, and can readily be protected by the owner. The reasons why fire protection is imperative are much the same as those given under grazing. The smaller trees are usually killed outright, and the larger trees suffer wounds which offer ingress to rot fungi, but the greatest injury comes in the destruction of the !eaf mulch. A single burning may destroy the accretion of years, and repeated burnings, like grazing, result in the formation of a sod. 110 Intinois Narurat History Survey BULLETIN Insects and fungous diseases. The application of insecticides and fungicides and other measures feasible for the protection of valued orna- mental and fruit trees are not ordinarily practicable in the woodlot. If a disease or insect attack takes on the proportions of an epidemic, the woodlot owner as an individual usually can not successfully combat it. Such epidemic conditions occur throughout the country both as disease infections and insect infestations. The attacks of a particular disease or insect are generally limited to a certain tree species or genus; they vary in intensity, and in an extreme form they may affect every tree of the species in the region. Disease epidemics on native chestnut are spreading throughout the range of this species so completely that native chestnut seems sure to disappear from our forests. No successtul method has been found to combat it. In sections of the Northeast, Lake States, and Northwest where the white pine blister rust has caused serious loss, organized protective measures have been adopted. Insect epidemic con- ditions are also common and often destructive. In the Northeastern States losses through infestations of the brown-tail and gypsy moths have reached millions of dollars; throughout the range of eastern larch, periodic epidemics of the larch sawfly eliminate this species from the for- est; in the West and South, the devastation of bark beetles destroys im- mense acreages of pines. In Illinois diseases have not reached such de- structive intensity as to eliminate completely any important species. In- sect damage, however, has been serious enough to restrict the use of cer- tain affected species. The black locust borer is so universally destruc- tive that the use of black locust for post production is advisable only under exceptional conditions. Trees of the black oak group are being killed by a flat-headed borer. Ash and cottonwood are dying in large numbers as a result of the attacks of scale and bark-boring insects. Where marked disease and insect injury are present in our woodlots, it is usually a result of poor forest conditions. The remedies lie in practicing forest hygiene and in destroying diseased trees and those which harbor borers. It should be the rule to remove trees as soon as they show evidences of weakness and stagnation. If bark borers are present in a living tree, it should be cut and peeled, and the bark and tops burned. Identification of diseases and recommendation of remedial measures will be made upon receipt of a specimen by the pathologist of the Natural History Survey, Room 219, Natural History Building, Urbana, and of insects by the entomologist at the same address. A MANUAL OF WoopLoT MANAGEMENT 111 ADAPTATION OF TREES TO SOIL To get the highest production from the woodlot, it is essential not only that the trees should be given protection so that they can be carried to harvesting maturity but also that they should be suited to the site and market demands. The average growth rates of different species of trees vary greatly, even when they are growing under similar conditions. Once the choice has been made as to what form the output of the woodlot should take, the woodlot should be managed with the object of favoring those most rapidly growing species which are suitable for the manufac- ture of these products. Studies of growth rates correlated with soil types made by the Natural History Survey,* show the relative values of the commoner soil types for tree growth and the relative growth rates of the species commonly found on each soil type. ‘ The best soils for timber production in this region are the bottom- land sandy loams, followed by the bottomland heavy loams, the upland loams, the sands, and finally the very compact loams or hardpan soils. If we give the least productive—hardpan soils—a rating of 1, the rela- tive productiveness of the other soils for unmanaged tree growth charac- teristic of each soil type is in about the following ratio: sands, 1.8; up- land loams, 2.3; bottomland clay loams, 2.8; bottomland sandy loams 6.3.. The above ratings, representative of unmanaged forests stocked with species whose presence in the stand is the result of natural forces, are probably very conservative for stands under management. In the latter, only the more rapidly growing species will be permitted to grow. The growth rates on the poorer soils are uniformly low, but with improved soil conditions not only do the growth rates increase, but there is also an increased number of the more rapidly growing species from which to choose. The prospects of raising the production on the hardpan soils through management of the woodlot are not encouraging, but on all other soils the managed woodlot is clearly capable of producing much better returns than the unmanaged. Tables II, III, IV, V, VI and VII show the average growth rates on these five general soil groups at 20-year periods in Illinois. The growth rates are indicated by the diameter inside the bark on the stump, by the height, and by the cubic feet of stem exclusive of bark. In a managed woodlot the growth rates should be more comparable to the even-aged figures as shown in these tables than to the all-aged figures. * Bulletin Vol. XVI, Art. I, Third Report on a Forest Survey of Illinois. (1926.) 112 TABLE II. AvERAGE GrowrH RATES ON UPLAND SANDY LOAMS IN ILLINOIS A and E indicate all-aged and even-aged stands, respectively Ittinois NaturAL History SURVEY BULLETIN HOO WABOHHARMD : 5 5 oto tmMoMmormMon ma WW “NO ‘euNpoA ALS SoRWAANAA H as) ec is} o te Hod HHOKBHOAND a Wi ‘WWSIOH ABH ADDAWAODO 2.|_ = Hat SOSSOHNCO ‘ul “q"t'd 19S DASIDIBANH NA Nninnnin NOODODAMWMOSS : a 4 co MANO MADD aS UUTOAS Ris N wesc eA n i S MHMOOHDOMODNS 2 WH ‘OsIeH DHE EHD~-CHOEEE WD o oo AHONAMNOMOOC OM 4 Wie * feel Soot a HOHE MHNNSCRAMA 2 Aninnnnninn MM romoaNn ont “qr 0 ‘aunjoA ela Re Cee Gebel eo Cait ee. wn H = AMO EAKLNCAnHMMMNDON ss 11 ‘Slo DOODODOONDODNONOSH ro) <— ANDDMDONDONONING “Parca |e ee ws icy oles oa ee cea eS i ar ee bon! HOM OWMOrwo “4a NO ‘eunjoA RM aAnNamdANdd n a cake s ARO HOIDM DIN WHA 2 “LA ‘T3190 EMO DAHHHOHO HHA So a ANtNMOMOANtE-OnHON ‘ul “q ‘td Td HOw His Hin co 09 ‘ Min tHOMMANA He “VND ‘eunjpoA wa SVP ia tee 2 8b NS” Satna er tare n mA _ 4 is} co) Ey in HOOCMAMHOHEO oH pb WI ‘WUS1I0H MANNAANANNAANAANT a ul “q‘1-a OMHAAINONAHDIMHO : He HABANA AGK Aq a qedadtddaqaid Ron pean ENDO sae RS n a eatraee Eruibiciclic. tes ceaa Rene a ine iets Pa ara ~ . . . . . . . o BMS, mins Use emcee: oy, = eerie Meme rarer a ee St a es eee B: ° ° ae aoe ay PCHES eins] eee cet tol ees oe Oe lo Sie Gi fs nakogo aos On n lt 1) Meo F eaattam oa ae etl ii te sl TABLE III. ILLINOIS IN Sirr Loams_ A and E indicate all-aged and even-aged stands, respectively AVERAGE GROWTH RATES ON UPLAND YELLOW AND YELLOW-GRAY A MANUAL OF WoopLotT MANAGEMENT | oOo © OD co 60CON 8 "7" ‘ Gtk Geb a) o m0 fF ey paol BUETITON S|) Si gar ee eR H Sal Gr eee ae a | coal CO . 4 WCOMME-NMORHAHTHM Ss Wi no ouINn[oA es . . . iy: . . . . - . n = a = =! 3 ie re AONHMHAMMANDSS S 147 ‘VQ3I0eH NAMANANAAHRHANHAN —} = aq - F WODOONDORMOWr ON HH UNE GI DOANMAMMHANHHON B@4A4t the dqaddae 2 Be SS n ae Dye h esac Sos 2 aoe 0 . : . 5 ;. c =| a 3 4. 3 eae A > 3 : ea as oy oe a ey Oe : : Bae n ene: Maa ON te at a. ry . i ° oo tS) ‘ Ss g o ) S) a Oo 2B Sy Pak RE uses So CP e@ue HO DK og so ra) ee} kn = Bam And oe 113 ie 5 a 5 is} re a > i 5 n m S fo) a x =| 3 E 4 a a 5 gq S| fe 114 | ; aad | LG OPT 9°&T $S 8°0T ra OF 9°) a GZ re W er yeo yovig | G° OF e) TLL L'9L 09 $ IL aa se gig et Cine se eee ms 0 eel « ele ee oo ee sae ysnool yor[q | 9°9T 29 0°IT ey LF e°8 ZL 92 Lt le PIC ECCI CECE RCICE Aa aC aC ECnCnC HC nC EC . eurd ou ys See seedee be | see ce ee lea ca |S Bee ees ee Ea oe el Bo RF i) ra = & ) © a 3 2 oy 5} sotoeds s1vod 08 S1vak 09 - SlBO0d OF sivok 0% ATPATJOedSaI ‘spue}S Pase-usA9 puB paseV-[[e e}vOIPUL FT pue VW SIONITT] NI GNVG NO SALVY HIMOUD IDVAGAV “AIT GIavL TABLE V. A MANUAL OF WoopLot MANAGEMENT AVERAGE GROWTH RATES ON HARDPAN IN ILLINOIS A and E indicate all-aged and even-aged stands, respectively baal at TN ‘OUINTOA s a 4 ee me ‘ tS a "Wa ‘TUS1EH 1S o a % “uy “q"t-a = seh ee = Ww ‘eunyjo, oS a baal a 2 Wa WUSIEH i518 o co S ~ ur “q"t-a nc = no WIND ‘euNjoA | ds + n 3 iS yw ysey | S35 3S =: Caer uqia| sax “wng ‘eumyoA se z n ~ = ANS > “Ml FUSTOET ||) => S — . ae . . aan Cie Es Cl aly esnesics “Yq no ‘eunypoA oS n a g qi VsIeH | ASS o N i . . Nox “ul “q ‘Td eo oS aR< ——~—m n e = 5 S) a a A nN oo hee $3 oe ® 6 Am A 115 eo a Intinois Natural. History Survey BULLETIN 116 ee | per | PL | 16 |/s°9 | OL |e9 |lo°e | 09 Ios Jjat | we jor |lF GLa aul victaces wets eieeeses dice | 0°eg gL eoevel|[ eevee &F eneee ice ewe cere s ens e[deur qos 9°ZET| LOT |8°Se |\e°F6 | OOT [8'Te |le-9S | 96 |z7zT |jo°oT | 29 Jes |W ccc aLOW BIAS | 6°Z2E| 800 12°72 ||2°9S | 96 ear ||m poomuo}}09 < | a e} < ef |} te} < ae] |S) S | 16 |8°9T |16°9F | G8 (2° 9T ||\2° Se | 69 Ih CT EL 8h |8°8 8° Go ECAH Nfaeee Orta ak See Eee qsv S'SOT! G6 |8°&s |/G° GL | 98 |9'Te |/0°8é 08 |0°9T ||2°OT | && |0°0T 6° 1Ké OF Whee oat eat uld | 9°16 | 88 |6°FS ||}9°09 | €8 [8° 6T |/F Te | co |8 eT GS | FE 87S || ¥ | 1°86 | 06 |h°S% |}0°SS | 08 |8°LT |/9°9E | 9 |e TE || LT | Pe OS a Woe oe “+ g[devur ajos S°9TT] 28 19°96 ||T'T9 | G8 [0°08 |]2' Te | $9 |F ET 0° | &€ De Ve “** ysnoo, AouoH 6° LP | 08 ee 6 Sa | 89 — 9) FE 0°S | LF Gok, |" "7" YSMOOT 19}B AA a et eae en eee Sete ae le (eu lue alee ae ee ae = ; = : | B 5 E Boke Beeb eet ote) a) aes ieee Heme ee | ee Nes Beaclacre att Ye | 5B |e |e oral EGAN mI ARs, eae GL OT sie gl ape gO Ue Sea erect |e eceue ae a >| 5B yy B 5B =] =) yj i=) Soloeds BAU doe ecaleeuies leauleenh ae) [reclaee!< Be] bl 2 | 3 by ¢ sf cts mel | a sived (OT sivak 08 | sivak 09 s.lBeak OF | sieak 0Z A]@PAT}OadSai ‘spuy}S pase-usaAe pue pase-[[e a}vOIpul WY puRe W SIONITIT NI SIUOG AAVA_ ANVINOLLOg ‘TIA SIdV.L NO SGLVY HEIMOUD AVUGAW 118 Intrnois NaTurRAL History SuRVEY BULLETIN An inspection of these growth measurements emphasizes the importance of eliminating the slow-growing species. The following list contains those slow-growing or otherwise undesirable species which are least suited to a place in the Illinois woodlot. WEED TREES Box elder Hackberry Black gum Elm Hard maple Redbud Hop hornbeam Ailanthus Buckeye Dogwood Shortleaf pine Jack pine Shadbush Persimmon Aspens Crabapple Pawpaw Beech Scrub oak Tupelo gum Birch Butternut Cypress Hickory Red cedar Arbor vitae Table VIII is a compilation of those species which are recommended because they have high growth rates and have the mechanical properties necessary for the production of the given product. The fastest growing species are listed first. Tasie VIII List oF SPECIES RECOMMENDED FOR SPECIFIC Sor CONDITIONS AND PRODUCTS FOR BOTTOMLAND Flooded for long periods j Not flooded for long periods Light Soils Heavy soils Heavy soils Light soils For Production of High-Grade Veneer Logs Red Oaks | Red oaks | Black walnut | White oaks White oaks | White oaks | Red oaks | Red oaks 4 : i | White oaks | For Production of Posts Catalpa Catalpa Catalpa | Catalpa White oaks White oaks Mulberry | Mulberry | White oaks White oaks | | Black walnut | Sassafras A MANUAL OF WoopLoT MANAGEMENT 119 FOR BOTTOMLAND—Continued. Flooded for long periods | Not flooded for long periods | Light Soils | Heavy soils Light soils Heavy soils | | For Production of Piling Pin oak | Pin oak | Pin oak | Pin oak Red gum | Red gum | Sycamore | Sycamore Sycamore | Sycamore | Red oak | Red oak Red oak | Red oak | White oak White oak White oak White oak | Black oak Black oak Black oak Black oak | Shingle oak | Shingle oak Shingle oak Shingle oak | Ash Ash Ash | Ash | | For Production of Ties Sycamore Sycamore | Sycamore Sycamore Ky. Coffee tree Ky. Coffee tree Black walnut Ky. Coffee tree Honey locust Honey locust Ky. Coffee tree | Honey locust Pin oak Pin oak Honey locust Pin oak Red oak Red oak | Pin oak Red oak White oaks White oaks Red oak White oak Black oak Black oak | White oak Black oak Shingle oak Shingle oak Black oak | Shingle oak Ash Ash Sassafras | Sassafras Shingle oak Mulberry | Mulberry Ash Ash For Production of Lumber Cottonwood Water locust Cottonwood Sycamore Water locust Sycamore | Sycamore Soft maple Sycamore Soft maple Black walnut Coffee tree Soft maple Coffee tree | Soft maple Honey locust Ky. Coffee tree Honey locust | Coffee tree | Pin oak Honey locust Red gum Honey locust Red oak Red Gum Pin oak Tulip White oak Pin oak Red oak Pin oak | Black oak Red oak White oak | Red oak | Ash White oak Black oak White oak Shingle oak Black oak Ash Basswood | Ash | Shingle oak Black oak Shingle oak Ash Shingle oak | 120 Ittinois NATuRAL History SuRvEY BULLETIN FOR BOTTOMLAND—Concluded. Flooded for long periods | Not flooded for long periods | i ; | | | ; Light Soils | Heavy soils | Light soils | Heavy soils | | For Production of Mine Timbers Sycamore Sycamore Sycamore .- Sycamore Coffee tree Coffee tree Coffee tree Coffee tree Catalpa Catalpa Catalpa Catalpa Honey locust | Honey locust Honey locust Honey locust Red gum | Red gum Red gum Red gum Pin oak Pin oak Black walnut Pin oak Red oak | Red oak Pin oak Red oak Black oak Black oak Red oak Black oak White oaks White oaks Mulberry White oak Shingle oak Shingle oak Black oak | Shingle oak Ash Ash White oak | Ash Shingle oak Ash For Production of Slack Cooperage and Average Veneer Logs Cottonwood Sycamore Cottonwood | Sycamore Sycamore Water locust Sycamore | Soft maple Water locust | Soft maple Soft maple | Coffee tree Soft maple Red gum Coffee tree Honey locust Coffee tree Honey locust Honey locust Ash Honey locust Coffee tree Willow | Red gum Ash Tulip | Willow Basswood | Ash Ash | For Production of Cordwood Cottonwood Sycamore Cottonwood Sycamore Sycamore Water locust Sycamore Soft maple Water locust Soft maple Soft maple Coffee tree Soft maple Coffee tree Coffee tree Honey locust Coffee tree Honey locust | Honey locust Pin oak Honey locust Red gum Black walnut Red oak Red gum Pin oak Pin oak White oak Pin oak Red oak Red oak Black oak Red oak White oak | Willow | Shingle oak Willow Black oak Tulip Ash White oak Ash Magnolia Black oak Shingle oak Basswood Ash Black oak Shingle oak White oak | Shingle oak Ash A MANUAL OF WoopLoT MANAGEMENT Tasre VIII—(Continued) 121 List OF SPECIES RECOMMENDED FOR SPECIFIC Sort CONDITIONS AND PRopUCTS FOR UPLAND Sandy Loams | Silt Loams | Sand | Hardpan | | For Production of High-Grade Veneer Logs Black walnut Black walnut | | Black cherry Red oaks | Red oaks White oaks | White oaks | Black cherry | For Production of Posts Catalpa Catalpa Sassafras Post oak Mulberry Mulberry | Black locust Black walnut Black walnut Osage orange White oaks White oaks | Sassafras | Sassafras Black locust Black locust White oak For Production of Piling White oak Black walnut Ky. Coffee tree Honey locust Cherry Red oak Black oak Shingle oak White oak Sassafras Mulberry Black locust Ash For Production of Ties Black walnut Ky. Coffee tree Honey locust Cherry | Red oak Black oak Shingle oak White oak Sassafras Mulberry Black locust Ash Red oak Black oak Black locust White pine Black walnut Tulip Magnolia Black cherry Coffee tree Honey locust Red oak White oaks Black oaks Basswood Ash Shingle oak For Production of Lumber White pine Black walnut Tulip Magnolia Black cherry Coffee tree | Honey locust Red oak White oaks Black oaks Basswood Ash Shingle oak White pine Red oak Black oak ILLINOIS NATURAL History SuRVEY BULLETIN FOR UPLAND—Concluded. Sandy Loams Silt Loams Sand Hardpan For Production of Mine Timbers Black walnut Black walnut Red oak Red oak Coffee tree Coffee tree Black oak Black oak Honey locust Honey locust Sassafras Post oak Catalpa Catalpa Black locust Sassafras Sassafras Red oak Red oak Black oak Black oak White oaks White oaks Mulberry Mulberry Ash Ash Black locust Black locust For Production of Slack Cooperage and Average Veneer Logs Coffee tree Honey locust Tulip Magnolia Basswood Ash Coffee tree Honey locust Tulip Magnolia Basswood Ash Black walnut Coffee tree Honey locust Tulip Magnolia Black cherry Sassafras Red oak Black oak White oak Mulberry Basswood Ash Black locust For Production of Cordwood Black walnut Coffee tree Honey locust | Tulip Magnolia Black cherry Sassafras Red oak Black oak White oak Mulberry Basswood Ash Black locust Sassafras Red oak Black oak Black locust Red oak Black oak Post oak ——— OO A MANUAL OF WoopLoT MANAGEMENT 123 EVEN-AGED SYSTEM OF SILVICULTURE A silvicultural system is a broad plan of management under which a forest is reproduced and developed. The two general types of forests which can be developed are even-aged and all-aged. LEven-aged forests contain trees of approximately uniform size, all of which reach harvest- ing maturity and are cut at approximately the same period; all-aged forests, as the name implies, contain trees of varying ages and sizes. No system based upon the idea of clear cutting is well suited to our Illinois woodlots. One important function of the woodlot is to supply the farm requirements for certain wood products. A clear-cutting system results in the formation of an even-aged stand, incapable of yielding any products until it has passed through the sapling stage. The returns from the even-aged stands are periodic, and the interval between periods of returns is so long that the interest compounded on the maintenance costs— protection, taxes, cleanings—may completely absorb all proceeds. To il- lustrate the influence of compound interest where returns are deferred: if taxes of $0.50 per acre per year are paid for 30 years while the stand is going through the sapling stage, the actual outlay for taxes totals $15, but the interest on these payments compounded at the rate of 5 per cent totals $18.44. On the average upland soils, at least 60 years are required to produce hardwood trees large enough for ties or small sawlogs. At $0.50 a year, the total outlay for taxes is $30 per acre, but the interest on this amount, when compounded over this period at 5 per cent totals $146.79. On this basis of calculation, only trees of exceptionally rapid growth and high value can show a profit when grown in even-aged stands. A discussion of the even-aged system follows. Even-aged woodlots are common throughout central and northern Illinois. The economic conditions by virtue of which such stands orig- inated and developed are rapidly altering and should force the complete clearing of these stands on the high-grade agricultural land-and should lead to their alteration to all-aged stands on the true forest lands. During the three decades prior to rail transportation when the tide of immigrants settled the prairies, there was a tremendous drain upon the local forests, amounting almost to clear cutting. The plow at the same time stopped the sweep of destructive fires, and the removal of the old forest and the cessation of fire was closely followed by the natural reestablishment of young trees. With the advent of the railroad, these young trees were permitted to grow, since construction materials and fuel requirements were supplied from other regions. Pressure for cleared land has sub- sequently resulted in clearing arable areas occupied by this second growth, thus incidentally supplying the farm with certain wood products, but very little cutting has been done in the stands which remain. The major- ity of these even-aged stands grow on upland sites and are between 60 and 90 years in age, and the diameters fall between 8 and 18 inches. ULLETIN YB LD URAL History SuRV INOIS NAT ILi 124 *se01} JO puvjs AAvoy Aq popeys [[9M PUL SALE, YIIM Pojodieo punoy ‘NVQ FLIHM PNOOX JO GNVLG GaDV-NGAG A MANUAL or WoopLor MANAGEMENT 125 As the timber famine becomes more acute, the farmer will draw up- on these woodlots for his requirements, gradually changing them to all- aged woodlots. But since the even-aged type usually follows clear cutting or the natural and planted reforestation of abandoned fields, there will always be stands of this character. The practice of growing wood crops in even-aged stands is more applicable to bottomland than to upland regions. On the bottomlands sub- ject to inundation, natural regeneration after a clear cutting is a cer- tainty, although it is very difficult to control the kinds which seed in, because the floodwaters deposit seeds from outside sources and carry away seed from local sources. Plant growth on such bottomlands is usually rank—weeds, vines, and worthless trees are very aggressive—and under an all-aged, or selection, system constant work is necessary to prevent the useless species from suppressing the useful. The unbroken canopy of the even-aged stand offers less favorable conditions for climb- ing vines. Certain useful bottomland species have very rapid growth rates; yet these trees are often intolerant of shade, developing better in even-aged stands. Finally, tall straight stems suitable for piling can best be developed in even-aged bottomland stands. Under these condi- tions it may be expedient to use an even-aged system. The management of even-aged stands is less complex in many re- spects than that of all-aged stands. The process may be divided into (1) development of the crop, (2) harvesting, and (3) reestablishing of a new crop. The proper development of the crop is attained through pro- tecting the area so that an abundance of trees may grow and through the judicious use of the axe so that the maximum growth may be con- centrated on the trees which are carried to the final harvest. The natural reestablishment of a new crop can usually be secured by observing a few rules at the time of harvesting the old crop. DEVELOPMENT OF AN EVvEN-AGED STAND The stand on the well-stocked acre starts with several thousand small trees. In a few years these become a thicket of saplings. The struggle for light at this stage is very intense, as each tree races upward in the effort to overtop its neighbor. When the polewood stage is reached, there are approximately 400 trees per acre, ranging in diameter from 2 to 10 inches. The increasing height brings added difficulty in transporting supplies from root to crown, and the height growth slows down. At this stage, trees must have room to expand laterally in order to make the best growth; hence, thinnings should he made. This is the oppor- tunity to insure the representation of desirable trees in the final crop by cutting into the following classes: (1) undesirable species (see p. 118). and (2) trees of desirable species but poor form. The forest tree should be tall and straight with a relatively short crown and a Jong stem. The thriftier trees of the desirable species which should be carried to maturity 126 Ittrnors NAtTuRAL History Survey BULLETIN are less than half the number present, but the rule should be to thin lightly, cutting only those trees which are directly interfering with the development of the select trees. In general, not more than a quarter of the trees should be taken out in any thinning, and the crowns of the trees left should close the canopy in 5 or 6 years. All material which can not be utilized should be left on the ground to decay. It should not be burned except in the emergency of insect or disease attacks. When it is evident that the trees are again suffering from crowding, other thin- nings should be made. The average numbers of trees per acre on un- managed even-aged stands at different decades are shown in Table IX. The heavy mulch of leaves and humus, a characteristic of good for- est conditions, can not be maintained if excessive thinnings occur. The appearance of grass and weeds in abundance after a thinning is evidence that it was excessive. Even-aged stands are often free from an under- story of bushes and shrubs, and if not, the owner considers it good prac- tice to clear them out. Such an understory should not be cleaned out. It protects the forest floor by its shade and retards the movements of drying air. Indeed, it is advisable to provide a thicket of bushes along the southern and western borders of the woodlot exposed to dry winds prevailing from these points. HARVESTING THE CROP Under the even-aged system a stand may be harvested in a single operation or by a series of cuttings. Such cuttings should not be ex- tended over too long an interval—more than 20 years—since young trees usually appear after each cutting and the succeeding stand loses its even- aged character. REESTABLISH MENT Following the removal of an even-aged stand, the area may be re- stocked by sprouts or seedlings or both, or restocking may fail completely ; therefore, a knowledge of conditions favorable to regeneration is essential to intelligent management. REGENERATION FROM SPROUTS Common Illinois hardwoods show a capacity to send out sprouts when trees are cut under certain conditions. These sprouts grow rap- idly for several years, but trees developing from them do not eventually attain the dimensions of trees grown from seedlings, and rot commonly enters the sprout through the decay of the stump to which it is attached. The, sprouting capacity weakens and is lost as the tree matures. For these reasons, stands of sprout origin are not well suited to the develop- ment of trees for the larger logs, nor can stands be renewed through sprouts from these larger stumps. This method of regeneration is, however, silviculturally suited to stands handled on a short rotation for the production of posts, cordwood, and mine timbers. The trees should be cut during the dormant season; ~1 A MANUAL OF WoopLor MANAGEMENT 12 TasLe IX. AVERAGE YIELDS FROM EVEN-AGED STANDS IN ILLINOIS ] | | = No. of | Height |D.B.H. of, Basal Yields mer Average Age trees | of domi- average area eos = annual in- Years per inant trees. trees | per acre ae = crement acre Feet | Inches Sq. Ft. eheae el ae oi | | (Upland) Post Oak Type. (Based on 14 Plots) 20 1,025 22 2.8 45 | 250 | 12.5 30 | 775 | 29 | 3.6 56 | 420 | 14.0 40 605. 35 | 4.4 63 | 610 | 15.2 50 470 | 40 5.1 67 775 15.5 60 360 43 5.9 69 | 950 | 15.8 70 285 46 } 6.8 71 | 1,150 16.4 80 235 49 7.5 73 | 1,360 | 17.0 90 195 | 51 8.4 75 | 1,550 | 17.2 100 170 52 921 art 1,780 | 17.4 (Upland) Scrub Oak Type. (Based on 23 Plots) 20 1,035 25 2.9 47 450 | 22.5 30 670 | 36 | 4.0 59 | 775 | 25.8 40 400 | 46 5.6 | 68 1,075 | 26.9 50 260 54 ues 75 | 1,400 28.0 60 180 61 91 81 1,750 29.2 70 120 67 11.6 88 2,075 | 29.7 80 90 72 | 13.8 93 | 2,375 | 29.7 90 75 74 ae | ae ] 2,650 29.4 100 65 77 Sos ets | 2,920 | 29.2 (Upland) Upland Hardwood aa. (Based on 34 Plots) 20 1,010 3.6 72 | 810 40.5 30 630 47 4.8 79 | 1,175 39.2 40 j 400 55 6.5 84 | 1,520 38.0 50 250 61 8.1 | 89 | 1,870 37.4 60 185 66 9.5 94 2,175 36.2 70 155 70 11.0 99 2,500 35.7 80 130 73 12.5 103 | 2,825 35.3 90 110 | 75 13.9 106 3,125 34.7 100 100 | 78 15.6 | 109 | 3,425 | 34.2 (Bottomland) Rapidly-Growing Species. (Based on 8 Plots) Cottonwood, Sycamore, Soft Maple, Honey Locust, Sweet Gum 20 450 | 75 6.0 | 87 | 2,450 | 122 30 290 82 8.6 118 | 3,400 } aus 40 230 } 87 10.2 130 | 4,180 | 104 50 205 | 90 | 10.9 137 | 4,930 | 99 60 | 190 92 | aha Deny 143 5,600 | 93 70 165 94 | 12.7 146 6,150 | 88 “(Bottomland) Slow-Growing Species. (Based on 11 Plots) Oak, Elm, Ash, Hickory 20 1,100 42 3.5 7 1,075 | 54 30 | 530 53 5.4 84 1,560 | 52 40 330 62 fdiset: 92 2,000 | 50 50 250 69 8.5 98 2,375 | 47.5 60 200 | 76 Hare | 104 2,675 45 70 170 81 10.8 | 109 | 2,950 | 42 80 145 85 12.0 } 113 | 3,225 | 40 90 125 88 13.0 116 3,500 | 39 100 110 91 14.0 118 3,750 | 37.5 128 Ittinois NATURAL History SURVEY BULLETIN the stumps should be low, and it is preferable to cut the top of the stump on a slant to allow water to drain off. Trees cut during the growing season exhibit a weakened sprouting capacity, and the sprouts are fre- quently killed by the autumn frosts before the tender tissues harden. Sprouts from low stumps are usually more vigorous, and conditions are less favorable to the decay of stems than in trees growing from high stumps. The sprouting capacity varies for different species, but, in gen- eral, stumps should not be more than a foot in diameter for good re- sults. It usually happens that too many sprouts develop and a thinning becomes necessary. ‘This should be made in the early sapling stage when the crowns are closing and crowding each other. The object is to leave plenty of thrifty stems to form the stand but to cut out the less desirable ones which are crowding the others. Frequently the thinning is cheapened by lopping off the tops of undesirables with a machéte or a bush hook sufficiently to check them and permit the desirables to get above them. REGENERATION FROM SEED In case the stand is carried past the period of vigorous sprouting— about 60 years for most species—, provision should be made for seedling reproduction or for replanting. The two different methods of securing natural seedling regeneration are as follows: 1. When the old crop is removed in a single cutting, the operation should take place after the trees have matured a heavy seed crop. Since heavy seed years vary somewhat for different species, best results are attained by selecting the species which is sufficiently well represented to insure the proper amount of seed production and which is the most desir- able tree to grow, and then by clear cutting the area immediately after this species has matured a heavy seed crop. The layer of leaves which covers the ground under normal forest conditions is very favorable to the es- tablishment of heavy-seeded trees, such as the oaks and vuther nut trees; it is unfavorable to the seeding in of elm, ash, tulip, and otlier light- seeded trees. In logging the area, the ground will be torn up somewhat, making spots favorable for the establishment of seedlings. The device of burning this leaf carpet will secure excellent results for light-seeded species if a favorable seed year is followed by a moist growing season; but this combination can not be assured. Therefore, as a failure to re- establish the forest under natural seeding is irrevocable after the seed trees have been cut, a burning is not recommended. 2. In order to positively insure the satisfactory restocking from the trees of the crop to be harvested, the stand can be harvested in two oper- ations. The first cutting removes about 40 per cent of the total number of trees and, by opening up the stand, creates light and heat conditions favorable to the establishment of seedlings. The trees removed in this first cutting are those of undesirable species or form; the 60 per cent left should give character to the succeeding stand. When seedlings ap- pear abundantly in the openings, these remaining trees are removed. Since a a a Se a A MANUAL or WoopLor MANAGEMENT 129 all seed trees are not cut until seedlings are established, this is the safest method of securing seedling regeneration from an even-aged stand. Un- der this system a light burning previous to the falling of the seed crop is justified where the leaf litter is heavy and where it is desired io secure seedlings from light-seeded species. APPLICATION OF THE EVEN-AGED SYSTEM Species suitable for production of piling Temporary piling includes any sound timber that will stand driv- ing, such as ash, beech, birch, cherry, sap cypress, sap white oak, red oaks, maple, black gum, and sycamore. In the application of the even- aged system to the production of piling, the object is to grow tall straight trees. Trees of this form can best be produced on fertile bottomland sites. Red gum, pin oak, and sycamore, especially in youth, develop a long narrow crown, and the main stem continues to the top. A great number of trees of this form can be grown per acre; consequently, for piling production these species rate high. Planting, or artificial regeneration, is not economically justifiable ; hence, dependence must be placed upon natural regeneration. An abund- ance of seedlings can be secured on cleared bottomlands if light and soil conditions are favorable; a full stand is assured on all cleared, unsodded floodlands, but usually the stand is a mixture of many species. To produce tall straight stems, the trees should crowd each other dur- ing the sapling and Spolewaod stage, so that no heavy side branches are formed. Thinnings can usually begin when the larger trees of the stand are a foot in diameter breast high (12 inches D. aE els) ie Pin oak on fertile bottomlands produces a 30’ to 35’ pile in forty years, and unmanged stands contain as many as 60 trees to the acre suitable for piling. Intolerant species, exemplified by cottonwood Those tree species which are not shade-enduring are classed as “intolerant”. Sycamore and soft maple belong in this class, but the Carolina poplar, or cottonwood, is the outstanding example of a rapidly- growing intolerant tree which should be grown in even-aged stands. Cottonwood trees make phenomonal growth on all but the heaviest bottomland soils, the logs find a ready market at excellent prices at mills specializing in fruit and egg containers, and the cordwood fur- nishes 50 per cent of the pulpwood grown in Illinois. Cottonwood has been successfully grown in plantations by the prairie farmer, has been developed into a profitable commercial project in South America, and is being developed commercially on Illinois bottomlands. There is no wood crop in Illinois which promises better returns than this species. 150 Intinois NATuRAL History SuRVEY BULLETIN Cottonwood seeds in naturally on bottomlands where the moist mineral soil is exposed to full sunlight. It does not seed in on ground covered with a layer of leaves or a heavy growth of weeds, nor will it survive if planted under the shade of other trees. Pure stands have come in naturally on river bars and similar deposits and on patches of abandoned plowland. The embankments of levees and drainage ditches are quickly marked by a line of cottonwoods. This species grows best on the alluvial sandy-silt loams; it grows well on alluvial sands and loams, but poorly on ill-drained alluvial clays. Although well able to grow on the floodlands subjected to repeated inundations, cottonwood does not grow in swamps where water stands continually or on the very poorly drained clays otherwise well above water level. Cottonwood matures an abundant crop of seed practically every year during the latter part of May and the early part of June, but these seeds must find favorable seed-bed conditions immediately, for they begin to lose their vitality within a week and are dead within a month. The pistillate, or seed-producing, flowers are borne on different trees from the staminate flowers. At maturity the pods open and liberate immense quantities of tiny brown seeds. Each seed is provided with a tuft of long silky hairs which enables it to be readily carried long distances by the wind. Ripening at a period when the larger rivers are at flood, the seeds are also transported long distances by water; but floods may also submerge an area past the germinating period of the seed, thus effectually keeping cottonwood out. ‘This, together with the aggressiveness of weeds on open bottomland areas, has led to the practice of planting such areas to cottonwood rather than depending upon a natural seeding. The methods of planting are outlined on pp. 152-154. When light and soil conditions have chanced to be just right, cot- tonwood has come in on bottomland sites in immense numbers; but since it is a tree which requires abundant sunlight throughout its life, only a very few of the most vigorous trees survive the sapling stage; the stand then opens up, and less valuable but more tolerant trees grow as an understory. A bad cutting practice of harvesting all trees above a merchantable diameter has been developed to conform with market conditions. A few years later some of the survivors have reached a merchantable size and are cut. Meanwhile, the shade has been sufficient to keep out cottonwood seedlings, but insufficient to keep out elm, soft maple, hackberry, and other less valuable trees. This cutting practice should be changed to a single clear cutting followed by a fire which thoroughly cleans off the ground cover in order to cre- ate seed bed conditions favorable for another crop of cottonwood. A MANvuAL or WoorLor MANAGEMENT 131 SELECTION SYSTEM OF SILVICULTURE The system generally best suited to the woodlot is termed the se- lection system. It consists in harvesting trees singly or in small groups and in regulating the cuttings so as to bring the stand to produce about the same number of mature trees in each cutting period. In the fully- stocked woodlot the total amount cut at any time should balance the total amount grown since the previous cutting was made. Under in- tensive management the mature trees are harvested annually; hence, the total amount of wood per acre removed should equal the annual growth of the acre. The usual practice is to fix a minimum diameter limit and to cut each year all trees which attain this limit, carrying on at the same time such cuttings in the lower-diameter classes as may be necessary to facilitate the growth of the trees to be carried to maturity and to free the stand from undesirable trees. Under this method the woodlot contains trees of many sizes; thus the diverse requirements of the farm can at all times be supplied. Since some trees are har- vested annually, the value of these can be balanced against the annual maintenance costs—protection, taxes, cleanings—, and there is no com- pounding of interest over long periods. GENERAL CULTURAL MEASURES Whether the woodlot be managed for the production of the small products, such as cordwood, posts and mine timbers, the intermediate products, such as ties, piling, ordinary sawlogs, or the large products, such as veneer logs, the general cultural measures are similar. The first concern should be to insure proper conditions for regeneration. This means, first of all, the absolute protection of the area from fire and grazing. Under natural forest conditions, where fires and live-stock are kept out, the layer of leaves gives place to a rich, moist layer of partly- decayed organic matter, under which is the mineral soil. Small seeds to some extent sift through the layer of leaves; the sprouting acorn or nut can push through to the rich humus and finally to the mineral soil. The removal of this layer of leaves and the exposure of the humus or bare mineral soil is usually highly conducive to the establishment of seed- lings, but the leaves should not be removed, because satisfactory regenera- tion can usually be established with the leaves present and because the injury to the soil through the destruction of leaves and humus outweighs all benefits. Where fires have repeatedly run through the woodland or cattle have freely grazed, the conditions are quite different. Instead of a mellow moist soil, there is hard dry surface or, if sufficient sunlight, a sod. Keeping fire and cattle out will usually bring back the forest trees if there is no sod; but, if a sod has formed, more intensive measures are Irninors NATURAL History SURVEY BULLETIN ED, OR SELECTION, TYPE. ALL-AG Abundance of trees. Ground carpeted with leaves. A MANUAL OF WoopLoT MANAGEMENT 133 necessary to restore the forest, as germinating seeds can not establish themselves under such conditions. Any agency which breaks up the sod, be it harrow or hogs, is useful; but the best means and often the only sure method of securing regeneration is to plant seed or seedlings in spots from which the sod has been removed. Where the woodlot is managed for the production of small products, satisfactory regeneration can be secured largely from sprouts. When managed for the production of medium and large products, this method can not be depended on, as the larger stumps do not sprout vigorously and the trees which develop from sprouts, although growing rapidly until the polewood stage is reached, do not develop into mature trees as large as those from seed- lings. After the woodlot has been managed under the selection system for a period long enough to secure good forest conditions, abundant natural reproduction is a practical certainty, and management will con- sist largely in trying to insure the establishment in sufficient numbers of the most desirable species. The rather common practice of marketing the valuable species from the woodlot without taking any positive steps to reestablish a valuable successor has resulted in a two-fold evil. The un- merchantable or low-grade species practically dominate the mature classes and deluge the area with seed. Thus the trees remaining in the woodlot have a low value, and these inferior species will perpetuate themselves and make up the succeeding stands. Management aims to correct this condition by weeding out the inferior species, thus lessening the seed supply and decreasing their representation in the reproduction, and by securing the establishment of desirable species, even resorting to planting when natural reproduction is not wholly successful. Since, under the selection system, the aim is to manage the wood- lot so as to bring about the same number of trees to cutting maturity each year, the area occupied by each age class should be approximately the same. If the average time required to grow trees suitable for mine timbers, cordwood and posts is 40 years, then each age class would occupy one-fortieth of the area. In actual practice this exact adjustment of age classes can not be attained, because of irregularity in regeneration and variation in growth rates, and because the annual yields from small areas often are insufficient to justify an annual cut. Although in theory the area occupied by each age class is the same, the number of trees in each age class is not. On average upland loams there will be something like 42 one-year-old trees and but 10 forty-year-old trees on the acre. In the case of such small products as mine timbers, cordwood, and _ posts requiring 40 years, only 400 out of 1000 trees are brought to maturity. In the case of sawlogs requiring 80 years, there are 600 trees per acre, 130 of which are carried to maturity. In the case of veneer logs requiring up to 150 years, only 80 would be carried to maturity out of a total of 36% trees. Since from 60 to 80 per cent of the total number of trees fail to reach maturity, it is not necessary to have more than half the repro- duction of desirable species. Thus, for small products, it would be 134 Intrno1is NATURAL History SURVEY BULLETIN considered satisfactory regeneration if 20 trees per acre of a desirable species were established annually; for logs, 4 trees; and for high-grade veneer, one tree of a desirable species per acre properly located will suffice. The young trees of the desirable species should, of course, be located in the openings formed by the removal of the older trees. Frequently, well-located young trees, which have become established before the older trees are removed, provide satisfactory successors to the matured trees. Commonly, young trees in abundance will appear in any opening; but if these are wholly of undesirable species or if, as in rare cases, reproduc- tion fails, it is advisable to plant seed or seedlings. Methods of planting seed and young trees are described on pages 138-142. The establishment of desirable trees in sufficient numbers is half of silviculture ; the other half consists in creating light conditions such that the trees to be carried to maturity will require the shortest time consistent with the production of trees of good form. Openings will always be made in the forest by the removal of mature trees and of other trees of un- desirable species, but one of the cardinal principles of cuttings should be to make as few openings as possible where the direct sunlight can reach the forest floor. Although from 60 to 80 per cent of the trees which start will not be carried to maturity, these trees perform the useful service of shading the forest floor and preserving moisture conditions decidedly beneficial to soil enrichment as well as to tree growth; and, in addition, by lateral crowding of the select trees during their immaturity, these others force them to rapid height growth and development into trees of good form, On the other hand, the competition for growing space be- tween all trees is keen, and, if unaided by thinnings, many of the de- sirable species will be crowded out by less desirable ones. Hence it is advisable to let all trees grow until such a time that the proper develop- ment of the select trees can not continue because of lack of crown space, and then to cut the undesirable trees which are competing with the select ones. The number of trees per acre or the regularity of spacing of the trees does not indicate whether the stand should be thinned, but rather the growing space available to the crown is the factor determining the necessity of a thinning. The critical examination is overhead. The rule should be to make light cuttings often rather than to depend upon heavy thinnings at longer intervals. Only through experience can the individual develop the skill and judgment by which he determines when crowding ceases to be a stimulus to height growth and becomes a check to proper development. Unutilized tops of felled trees should not be piled and burned, unless burning must be resorted to in order to check insects and fungous diseases. The brush should be scattered to lie close to the ground in order to facilitate decay. In woodlots managed for the production of cordwood, posts, and mine timbers, such thinnings would give products of little value; but in woodlots managed for the pro- duction of ties and logs, these thinnings should provide posts, cordwood and mine timbers. A MANUAL OF WoopLot MANAGEMENT 135 FIXING THE DIAMETER LIMIT The diameter of a standing tree is customarily taken outside the bark and at a point 4% feet from the ground. This is known as the diameter breast high, or D.B.H, and affords a convenient basis of classification. If the stand is kept fully stocked in the smaller-diameter classes, and if the area occupied by each class is approximately the same, then, by fix- ing a diameter to which the select trees must grow before they are harvested, equal quantities can be harvested each year, yet the cut is automatically balanced by growth. Not only are there certain products which give higher returns than others, but also the returns per acre, even for a given product, vary with the diameters of the trees harvested. The individual tree is unmerchant- able for a definite period of its immaturity; after it attains merchantable dimensions, the value increases rapidly as the tree increases in size. The higher value is due to the added growth and to the higher quality of growth. This increase in value continues as long as the tree remains sound and continues growth. Offsetting this increase in value as the individual tree gains in size is the fact that fewer large trees can be grown per acre. A refinement of management consists in fixing the diameter limit at the size which gives the greatest returns per acre. The accurate defining of the correct diameter limit for any given product and region requires a knowledge of the average time required to grow a tree to each diameter, the number of trees of any given diameter which can be grown on an acre, the quantities of the product which are produced per tree and per acre for each diameter class, and, finally, the net value of the product. The problem is further complicated by the constant increase in the value of forest products, an increase which often justifies holding trees beyond the time dictated by factors of natural growth. The local influence of market conditions, together with the vari- ation in the composition of different stands, permits the application of only very general statements to individual woodlots. It is a fact, however, that the smallest diameter at which a tree becomes merchantable almost never corresponds to the diameter at which the tree would give the best returns. It is not wise to cut thrifty trees of the lower-diameter classes which may be merchantable. ADVANTAGE OF LARGER DIAMETERS The rapid increase in value of the individual tree after it enters the mer- chantable class is brought out in studies of black oak on upland loam in Illinois Such a tree having a D.B.H. of 10” averages one tie worth $0.50; a 12” tree averages two ties worth $1.60; a 14” tree, four ties worth $3.80; a 16” tree, four ties worth $4.90; an 18” tree, five ties worth $5.70. It takes 52 years to grow 136 ILLinois NaTuRAL History SurRvEY BULLETIN the tree producing the $0.50 tie, and 103 years for the tree producing the $5.70 value. If the 10-inch tree is cut, the gross annual returns per tree approximate one cent; if the tree is allowed to grow to 18 inches, these returns are approx- imately 5% cents per tree. No information exists as to the number of trees per acre which can be grown to 10” D.B.H. in 52 years under the selection system, or to 18” D. B.H. in 103 years. In the absence of reliable data on the average number of trees per acre of a given diameter which can be matured yearly where the selection system has been practiced, recourse must be had to the data collected from fully-stocked even-aged plots. Table X gives data for such plots on upland loams in this State, the tabulation being in terms of the average D.B.H. of the stand. The average D.B.H., made up from all trees on the plot, includes trees of several diameters, and the yields assume that all trees which have attained a merchantable diameter will be cut, whereas in the selection system only those trees which reach the diameter limit chosen as the most desirable will be harvested. In order to make the data from even-aged stands directly applicable to a selection cutting, the rather doubtful assumption must be made that the number of trees on the even-aged plot of a given age and average D. B. H. is equal to the number of trees actually brought to this diameter in a selection forest over the same period. The number of ties which can be harvested from the larger tree until the 15-inch class is reached more than makes up for the decrease in the number of trees per acre. Above this diameter the increase in the number of ties per tree is not enough to offset completely the decrease in the number of trees per acre, and the total tie yield per acre decreases. Converted to gross returns, however, it often happens that the increase in value due to the higher quality of ties which can be secured from the larger-diameter classes may carry opti- mum gross returns into a larger-diameter class than that for the maximum num- ber of ties. The interplay of quantities and quality, as measured by gross annual returns per acre for ties shown in column 6, indicates that under average conditions of growth the upland woodlots give the highest gross returns on a 15-inch diameter limit. At this diameter these returns per acre are 1.65 times those when a 10-inch diameter limit is used. The same general principle, that it is not profitable to cut the low-diameter classes merely because there happens to be a market for them, holds for other products. Rather limited studies of black walnut on sandy loams in this State indicate that 1.58 trees averaging 14 inches on the stump can be matured per acre annually. Such trees average 50 years in age, and the average annual yield per acre is 63 B.F. of lumber logs worth $3.15 at the mill. If trees are carried until they attain a 26-inch diameter, only .57 trees per acre can be matured annually, and such trees average 140 years in age, but the average annual yield per acre is increased to 214 B.F. of veneer logs and 16 B.F. of lumber logs, totaling $23.54 at the mill. Thus the acre managed on the 26-inch diameter limit gives a gross return of 7.47 times that from the acre on the 14-inch diameter limit. A MANUAL OF WoopLotT MANAGEMENT TABLE X, 137 Yretp oF TIES PER ACRE ON UPLAND LOAM UNDER VARIOUS DIAMETER LIMITS No. of trees No. of é Height of | | annually ties ei Dominant Age | reaching annually Tree diam. harvested limit per A. Inches Feet Years | Ber A: 10 67 63 | 2.78 2278 11 70 70 ages 3.24 12 72 77 | Tet5 03.64 13 74 84 | 1.43 3.83 14 76 91 ie Saleal 3.98 15 77 97 Hel 06 4.02 16 78 104 0.95 3.92 17 78 | 111 0.86 3.80 18 79 | 117 0.80 3.73 | AV. annual gross re- turn per A Co Go Co Go Oo Oo Co IS bo annual gross re- turn per tree 138 Ittinois NaturAL History Survey BULLETIN PLANTING TO REENFORCE HARDWOOD STANDS Up to this point in the discussion of woodlot management, it has been assumed that natural reproduction is possible and advantageous, but there are conditions where planting must be resorted to. Tree plant- ing on the farm may be divided into two classes: (1) reenforcement planting within the woodlot, and (2) planting of cleared areas. The first of these will be discussed here, and the second on pages 143-163. The principle to be followed in reenforcement planting within the woodlot is to use those species which are not only adjusted to local soil and climatic conditions but which are also able to compete successfully with the associated native trees and to reproduce naturally under forest conditions. The conifers do not qualify for reenforcement planting among all-aged hardwoods in Illinois, because those having a sufficiently high rate of growth and value are intolerant of shade and are not well suited to woodlot conditions, nor will they reproduce and hold their place in a hardwood mixture. Black walnut, basswood, and red oak are recom- mended for woodlot reenforcement on those soils and sites adapted to these species as shown in Table VIII, p. 118. To these may be added tulip poplar in the southern part of the State. Brack WALNUT Black walnut is by far the best native hardwood for reenforcement planting. The tree can easily be grown from nuts, the wood is suitable for farm requirements, and the growth rate is relatively rapid. Logs of black walnut command a price virtually double that of any other na- tive hardwood, and good markets are accessible. A large percentage of the walnut now being marketed is coming from open-grown trees, and the practice is general of leaving seedlings which spring up in vacant places along fences or in pastures. Farm owners have found that walnut trees set out in plantations on high-grade arable land do not give re- turns at all comparable to those from ordinary crops, but that trees standing individually or in groups along roads, fences, streams, and hol- lows, or scattered about in the permanent pasture, are a source of revenue and warrant the slight positive effort necessary to increase their repre- sentation in such waste places. A walnut takes up no more room than an elm or hackberry and has a much higher market value. Black walnut is rather exacting as to soil requirements. It grows best on deep, fertile, well-drained loams with a stable moisture supply, such as are found along the flood-plains of the smaller streams, or in hol- lows and sheltered coves receiving the wash from adjacent uplands. It makes exceptionally rapid growth on sandy loams. It grows well on the moderately fertile, yellow and yellow-gray, silt loams characteristic of the A MANUAL oF WoopLor MANAGEMENT 139 rolling uplands of the timbered regions, and on well-drained, dark, prairie loams. It does not grow on sands or hardpan soils where acidity is high and moisture conditions are variable, nor on swampy areas. This species is also somewhat exacting as to light requirements. The seedling can persist under an overwood but requires full overhead light to develop; therefore, in reenforcement planting in a hardwood stand, walnut should be started in openings large enough to insure such light. This species should be used to supplant other trees which are removed, but there is a limit to the number which should be grown on an acre. It is a space-demanding tree, for the long branches extend almost at right angles to the axis. The canopy is also relatively open, so much so that in pure walnut stands enough light comes through to support grass. It can be grown in groups, but not more than half of the stand should be of walnut if proper forest conditions are retained. When grown in the open, the tree has a short trunk and wide-spread- ing crown. A tree developing a long clear bole can be produced by prun- ing off the lateral branches close to the trunk while the tree is in the sapling stage, or by pinching off the new lateral shoots as they develop during spring. Tutre PorpLar AND BAsswoop Tulip poplar and basswood are not valuable for ordinary farm re- quirements but are special-purpose woods, and should be grown in those woodlots tributary to a market. Good markets for tulip logs exist in southern Illinois and for basswood logs in both southern and northern Illinois. The natural range of tulip is limited to the southern part of the state, while basswood is of state-wide occurrence. Tulip is slightly more exacting as to soil and light requirements, but both species occur on all but extremes of sands and hardpan soils, and each can naturally establish itself and grow in hardwood mixtures. Tulip must have direct over- head light, being very similar to walnut in this respect. Basswood is rather shade-enduring, and can grow on heavier clays and wetter situa- tions than tulip or walnut, commonly being found on the stream banks as well as on the uplands. It is not advisable to plant basswood or tulip seed directly in the Wwoodlot, because the germination of the former is often delayed until the second year and the germination of the latter is uncertain. Other less desirable seedlings meanwhile establish themselves. Seeds should be planted in a seed bed as described on pp. 141-142. The proper time for sowing is in the fall. The proper number of seeds per foot of row is shown in Table XI (p. 142). In order to produce sturdy stock well able to compete in the woodlot, it is advisable to let the young trees grow two seasons in the seedbed, after which they can be transplanted to the woodlot. 140 Intinois NaturAL History SuRvVEY BULLETIN Oaxks Red oak, although it is a wood of only medium value for either farm or market purposes, is recommended as a sort of general-purpose tree, because it is one of the most rapidly growing oaks, because it can be easily grown on a wide range of soil conditions, and because its wood has so many uses that markets exist everywhere in the State. It is sub- ject to destruction through the attacks of a flat-headed borer and should not be used in those localities where this insect is killing the black and red oaks. Reenforcement can be made by planting acorns during the spring. METHODS OF PLANTING The term reenforcement planting has been used for planting done in openings where natural reproduction is not assured. On such blanks, once the desirable species is planted, there is but little danger that repro- duction of undesirables will crowd it out. But woodlot improvement does not stop with the operation of filling up the blanks with seedlings of valuable species. Such seedlings can be established where an abund- ance of reproduction of an undesirable kind exists. In this case the un- desirable reproduction must be cleaned away from the valuable in order that the latter may properly develop. Such a cleaning should occur at the time when the planting is made and be repeated at any stage of the competition when the undesirables overtop the planted trees. When the nut trees and oaks are used, the better method consists in planting the seed where the trees are needed. For basswood, tulip, and other light-seeded trees, the better method is to transplant seedlings where trees are needed. The acorns of the white oaks germinate in the fall and must be planted at this season; spring is the best time to plant acorns or nuts of the other oaks and nut-bearing trees, as fall-planted seeds are sub- ject to rodent destruction. The seed should be collected in the fall. It is a good plan to place acorns in a vessel of water and discard those which float buoyantly, as this minimizes the number ruined by insects. To store nuts or acorns over winter, place them outdoors in a small heap on a slight elevation where water will not stand, and preferably on well-drained sandy soil. Place a layer of straw or leaves over them and then throw dirt on this, but leave places where the straw ends project out at the side of the mound to insure ventilation. Freezing does not injure them, but as soon as the frost leaves the ground in the spring they must be planted, because acorns especially will quickly sprout at this time. Most of the black walnuts sprout the first year, but some walnuts will carry over and sprout the second year. In planting, two or three » a a ara A MANUAL OF WoopLoT MANAGEMENT 141 nuts are placed in a slight excavation where the tree is to be grown, and about 2 inches of soil packed over them. If squirrels are troublesome, it is advisable to make several seed spots where ultimately but a single tree may stand, or to protect the nuts by covering each one with a tin can from which the lid has been removed. ae ee a ND Se ee a I eS ee ne ge STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVIL BULLETIN Article IV. The Plankton of Lake Michigan BY SAMUEL EDDY PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS November, 1927 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol) XVII. BULLETIN Article IV. The Plankton of Lake Michigan BY SAMUEL EDDY PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS November, 1927 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. SHELTON. Director BOARD OF NATURAL RESOURCES AND CONSERVATION A. M. SUELTON, Chairman WILLIAM TRELEASE, Biology Joun W. Atvorn. Engineering Henry C. Cow es, Forestry Cuartes M. TuHomrson, Representing Epson S. Bastin. Geology the President of the University o} WitrttaM A. Noyes. Chemistry Illinois THE NATURAL HISTORY SURVEY DIVISION STEPHEN A. Fores, Chief ScHNEpP & BARNES, PRINTERS SPRINGFIELD, ILL. 1927 73484—1200 Illinois State Natural History Survey Bulletin Vol. XVII Art. IV. ERRATA es 208, 211, 214, 219—for Bacellariaceae read Bacillariaceae. 209, e 211, e 213, 215, e 218, 220, 224, 228, middle of table—for oligactus read oligactis. fifth line in table—for Aphanotheca read Aphanothece. first line in table—for oligactus read oligactis. fourth line in table—for acuminata Ehr. read acuminatum (Kutz.) Cl. sixth paragraph—for Aphanotheca read Aphanothece. fifth paragraph—for acuminata read acuminatum. fourth line from bottom—for Pandorin read Pandorina. Omit last line and read Traverse Bay region. fifth line from bottom—for Antario read Ontario. ee ee = VoLtuME XVII. ARTICLE IV. THE PLANKTON OF LAKE MICHIGAN SAMUEL EDDY The minute organisms constituting the plankton of the Great Lakes have been studied previously more in connection with investigations of their inter-biotic relations rather than from the primary aspect of the plankton. Perhaps the largest amount of work has been done by inves- tigators who were interested chiefly in the relation of the plankton to the white-fish industry. This is one of the most important phases of plank- ton work, because the white-fish as well as other fishes of the Great Lakes is dependent upon the plankton for food in its early life (Forbes, 1883 )— a fact which has made the study of plankton and plankton production most valuable. Other investigators have made fragmentary studies of the plankton of the Great Lakes for taxonomic purposes; Kellicott, Jennings, and oihers, for example, devoted their attention to the occurrence of certain groups of organisms and to the number and description of species in those groups as found in the Great Lakes. The chief purposes of this paper are: (1) to present a general pic- ture of the plankton of Lake Michigan, (2) to determine the relative abundance of its constituent organisms, and (3) to incorporate and sum- marize the facts now known relating to the plankton of the Great Lakes. Very little work of a quantitative nature has been published on this subject within the last twenty years. Previous to this period a number of qualitative investigations were made on the plankton of Lake Erie, Lake St. Clair, Lake Michigan, and Lake Superior ; and a very important work of both quantitative and qualitative character was done on Lake Michigan in the Traverse Bay region by the Michigan Fish Commission (Ward, 1896). In the latter investigations, which covered both bottom and plank- ton organisms, the gross quantity of the plankton was estimated from silk-net tows, and some idea of the general character of the plankton was obtained from the relative abundance of the constituent organisms. MeEtTHops AND MATERIALS The data for the present paper were obtained from two series of col- lections made from Lake Michigan in 1887-1888 and 1926-1927. Fifty silk-net tows (Table I) were made by the Illinois State Laboratory of Natural History from November, 1887 to November, 1888 from the break- water at Chicago. Quantitative silk-net and filter-paper collections (Table Il) were made October 16-17, 1926 at Indiana State Dunes Park and Michigan City, Indiana, and near Sawyer, Michigan. Quantitative collec- 204 Ittinors NaturAL History SurvEY BULLETIN tions (Table III) were also made May 14-15, 1927 at Dunes Park and Gary, Indiana, and July 10, 1927 at Chicago, Illinois. All of these were surface tows near the shore, so that the material in this paper relates only to surface and in-shore conditions. No investigation has been re- ported on the plankton or the conditions in the central area of the lake. The material of the older series of collections, which had been pre- served in formalin and glycerin, was found to be in excellent condition. Unfortunately, the accession numbers on some of these collections had be- come illegible, so that it was impossible to secure definite information in regard to the months of January, February, and March of the year 1888. The collections which were assumed to cover these months showed very little variation in the constituent organisms from those of the other months. PHYSICAL CONDITIONS Lake Michigan offers a very stable habitat for the production of plankton. Because of its large size and the lack of strong currents, the physical conditions of the water vary but slightly from year to year; therefore, the same constituent organisms may be expected in the plankton over a long period of time. Forbes (1883) found that the conditions of life in Lake Michigan were remarkably uniform throughout the sea- sons and from year to year and that both plant and animal life exhibited there a regularity and stability in remarkable contrast to their fluctuations in smaller bodies of water and on the surrounding land. There was little change, he found, in the relative number of individuals of the various species or in the absolute number of each. Shelford (Ward and Whipple, 1918) pointed out that Lake Michigan, being a large and deep lake, had none of the seasonal temperature changes extending to the deeper parts. Consequently, as only the surface temperature fluctuates, one would ex- pect the deeper portions to exert a more stabilizing influence on the sur- face waters than would be found in the waters of more shallow lakes. The stability of the lake as a biotic factor is strikingly demonstrated by our comparisons of data covering a period of forty years, for little or no change has occurred in the composition of the plankton over this long period. Many of the constituent species, though showing slight seasonal variations, are rather constantly abundant throughout the year. The south end of Lake Michigan is composed of gently-sloping sand beaches exposed to considerable wave action. In the northern portion of the lake there is some rocky shore line. Areas of mud flats and aquatic vegetation are rare. All these conditions are characteristic of a primitive lake. There is little variation in water level or shore line from year to year, and ‘overflow conditions are practically unknown. Cooley (1913) gives the following figures covering the water level for the years 1560- 1913: Greatest yearly range of Lake Michigan........ 1.94 ft. Least 7 ret a ae Ne Sn et ae ae .O9 ft. Average a se eaee ie Us Fite MAGN eiaas 1:21 ft ST THE PLANKTON OF LAKE MICHIGAN 205 At the south end the sandy character of the beaches and the strong wave action prevent the growth of vegetation with its consequent influ- ence on the conditions and life of the water. Practically all the plankton, therefore, must originate within the limnetic area. Shallow breeding areas such as Kofoid (1908) found in the backwaters of Illinois River are practically unknown, Adventitious species so common in the plank- ton of the shore and bottom areas of rivers and shallow lakes are rare. Stable conditions are insured still further by the extremely slow re- moval and renewal of the water in the lake. Speaking generally, Ward (Ward and W hipple, 1918) stated that great depth in a body of water and a large inflow in proportion are anfavorable to the abundant production of plankton, and Ward (1896) computed that there is a change of about one- eigh’ieth of the entire volume of Lake Michigan in one year. In other words, there are no extensive outflows to upset the conditions of life in this lake. The suspended organic matter and silt so common during overflows in rivers and other plankton-bearing waters—and so detrimental to the production of plankton organisms—seem to be at a minimum in Lake Michigan. (The turbidity was not recorded when the collections were made, but it never seemed to be very high.) All things considered, the conditions for plankton production in Lake Michigan approach those of the sea as near as do those of any body of freshwater. GENERAL CHARACTER The gross bulk of the plankton in the water, determined from the collections made in 1926-1927, is quite large. Ward (1896) reported that the plankton in the pcr two meters in the Traverse Bay region ranged from 8.9 to 14.12 c.c. per cubic meter, and that the abundance of the plankton gradually divibaiched(s in the lower levels. His data were ob- tained by allowing the silk-net collections to settle in a graduated cylinder and computing the volume of the plankton per cubic meter. The same method when used on the recent collections showed an even greater bulk for is surface plankton. The collections of October, 1926, averaged 10 c.c., and those of May, 1927, 40 c.c. per cubic meter. Some differ- ences in bulk may be due to time, locality, and seasonal variations. The heavy bulk of the May, 1927, plankton may be due to a spring condition, as Ward’s collections were made in summer. In general, the plankton of Lake Michigan is that which character- izes large and deep lakes. Its specific character consists principally of diatoms ca the genera Asterionella, Striatella (Tabellaria), and Fragilaria. Limnetic algae are not very conspicuous. Zooplanktonts are generally scarce in numbers, but always present to some extent. In the 1887-1888 collections the zooplanktonts, particularly those of the larger sort, were much more abundant than in the recent collections and sometimes com- prised nearly half the total number of organisms present. The absence of the smaller organisms in the older series makes it reasonable to as- 206 Intinors NATuRAL History SuRVEY BULLETIN sume that a coarser net must have been used, which would account for the loss of many of the smaller organisms and for the relative abundance of the larger forms. As quantitative methods were not used in making the 1887-1888 col- lections, it was impossible to calculate the total volume of plankton at any time during that period. Qualitatively, however, the older series was very similar to the recent series. At all times in the silk-net collections, the phytoplanktonts greatly outnumbered the zooplanktonts; the latter, however, made up for their smallness in numbers by their much larger individual size. Because of their spines and other peculiarities of shape, the plant species actually oc- cupied a great deal less space than they seemed to at first glance, or than their numbers would indicate. Careful measurements, with an ocular micrometer, of the average actual bulk of the various silk-net organisms showed that the zooplanktonts, although present in much smaller numbers than the plant species, often comprised nearly one-half the total bulk. Considerable variation of this ratio between the animal and plant con- stituents was shown in different collections, depending on seasonal and other factors. This ratio would not apply to the total plankton of the lake, because not enough data were obtained in regard to the smaller organisms (nannoplankton), some of which escaped through the net but were found in the few filter-paper collections. In all, 119 species were found, most of which were typical plank- ton species. More data on the nannoplankton would undoubtedly greatly increase this number. Sixty of these species were phyto- planktents and fifty-nine were zooplanktonts. This is only about one- fifth of the total number of the species listed in the various reports of previous investigators as accurring in the waters of the Great Lakes. Of the 66 species occurring in our 1887-1888 collections, 17 (at least three of which were adventitious) did not occur in our recent collec tions; most of these were never abundant and could have been easily lost in the later collections. Of the 102 species occurring in our 1926- 1927 collections, 53 were not observed in the earlier collections; these were either rare or, as previously mentioned, were so small as to escape through the meshes of the net. Many species of algae which were not noted in the earlier series showed up in the recent series, though none of them were abundant. There is no evidence that any of the missing species did not exist in both periods. Anyone familiar with the methods of plankton study can easily understand how some of the smaller organisms by their scanty distribution can easily escape collection and obseryation. The 49 species which were common to both periods were usually the larger and most abundant organisms. A rich diatom flora predominated in all the colles ieee! the same species occurring in both periods with few exceptions. Those species which were most abundant in the recent series appeared in the same pro- portions in the earlier series. THE PLANKTON oF LAKE MICHIGAN 207 The same species of copepods occurred in both periods with the not- able exception of Epischura lacustris Forbes, which was abundant in the early collections but did not appear at all in the recent ones.. The same species of cladocerans were scattered throughout both series. The Pro- tozoa and Rotifera, never abundant, were limited to a few common species occurring in most of the collections, and as they are hard to preserve for identification not enough good determinations could be made of most of them to establish their distribution. SEASONAL ASPECT The data are not extensive enough to justify any definite statement of seasonal variations in the bulk of the plankton, although the fall col- lections of 1926 showed only one-fourth the bulk of the spring collec- tions of 1927. Seasonal variations in constituent species were noticeably lacking, the dominant diatoms running almost uniformly through the col- lections of 1887-1888. Asterionella gracillima, reported as a spring species in the Hlinois River by Kofoid (1908), was abundant throughout the dif- ferent months, as also were Lysigonium (Melosira), Striatella (Tabel- laria), Synedra, and Fragilaria. Other less abundant diatoms generally appeared irregularly in the collections. Forbes (1883) concluded, from his own observations and those of B. W. Thomas over a period of six- teen years, that there was little change in the constituent organisms in Lake Michigan from one season to another, although he noted a sl ght increase in number of species in the spring and summer months. In the 1887-1888 collections, the zooplanktonts showed a decided decrease in the colder months, being almost entirely absent in the collections of Decem- ber and in those attributed to January, February, and March. GENERAL DISTRIBUTION A fairly uniform distribution of the plankton of Lake Michigan is to be expected, and very little difference has been noticed in the specific character of the plankton at different points. The off-shore waters of Lake Michigan are fairly well mixed by circulation; currents sweep south- ward on the west side, turn at the south end, and flow northward on the east side (Harrington, 1895), so that the water bearing the plankton at Chicago is, a few days later, off Michigan City, Indiana. In all the collections examined, the exact number of organisms was never the same, and absolute uniformity has never been reported in plank- ton investigations. A tendency to swarm is indicated by the variations in abundance in all collections. Reighard (1894) found evidence of plankton swarming in Lake St. Clair. Forbes (1883) found that the plankton was not equally distributed throughout the water and was more dense off the mouths of rivers. 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Ath 002 cts ve Bap fieco Pat acktr ey ariplintedstatwh sre eis) anwasticaeia tay eeere ius “***-UT91g BTRalNoR stxAdoiquep 20Z0}0dq (suoT}oeT[09 (SuoT}9e100 seded eee ye Rte aa (SUoT}09T[00 OUNTSZ) | TOMES) | egret sew |pzer ‘pt sew | POTS 2) suusTuRs10 LO6T ‘OT AINE ‘TIT ‘oseoryp LO6T PLAPIN “pul ‘yreqseunqd LO6T PT APIN ‘pul pul Ceres ‘ye qseung |‘yaeqsounq pepnpuop—III avy 217 THE PLANKTON OF LAKE MICHIGAN 08 000°08T “*| GOa'P 006°9T 0S9'T Ta "| 968 ‘ds snjdureooyyurep Fite teeeeereeeeseres ppodadop Suno x Z A "*-Tayosty Snursead sdopoAy sree esse sonery snyeptdsnoiq sdojoAp tere ese eee ees “TIT SIINUIM snwoJdeId ‘oes usreA Ipuepyse snuoyderd epodadog “-**(ayooq) I pury B1opoydery beet esses tees eteeeeeees ss Sipkary BurdsIsuo] Bulusog euvo0pe|9 218 IntiInor1s NATuRAL History SurvVEY BULLETIN NOTES ON CONSTITUENT ORGANISMS CYANOPHYCEAE (BLUE-GREEN ALGAE) The blue-green algae, never very abundant in plankton collections of Lake Michigan, were represented by a few species which were usually present in small numbers in most of our collections. Fourteen species were noted in all. Snow (1902) listed thirty-four species from Lake Erie. Ward (1896) noted several species from the Traverse Bay region. Whip- ple (Leighton, 1907) found three genera of blue-green algae in Lake Michigan at Chicago. Merismopedia: Merismopedia glauca (Ehr.) Nag. appeared in small quan- tities in the collections of June, 1888. Fragments of the plate-like colonies occurred in the plankton Oct. 17-18, 1926 at Dunes Park, Michigan City, and Sawyer, and May 15, 1927 at Dunes Park. The colonies were never very abund- ant, averaging about 200 per c. m., although 3,750 per c. m. were counted in the 1926 collection trom Dunes Park. Snow found this species in Lake Hrie. Ward recorded M. convoluta Breb. at Traverse Bay. Coelosphaerium: Coelosphaerium kutzingianum Nag. occurred in small numbers in the collections of Nov. 1887, Aug. and Sept. 1888, and Oct. 1926. The colonies reached a count of 90,000 per c. m. at Michigan City, Oct. 17, 1926. The absence of this species in all the spring collections suggests that it is not a spring form. Because of its small size and relative scarcity, it appeared to be of no great importance. Colonies of C. nacgelianum Unger were common (112,000 per c. m.) in the plankton July 10, 1927 at Chicago. Snow recorded C. Kutzingianum Nag. and C. roseum Snow from Lake Erie. Gomphosphaeria: Cclonies of Gomphosphaeria aponina Kutz. occurred only sparingly (4,000 per c. m.) July 10, 1927 at Chicago. This species was reported from Lake Erie by Snow. Aphanocapsa: Floating colonies of Aphanocapsa elachista W. & G. S. West appeared only in the collections made in the fall of 1926, when they were quite common. Colonies of much smaller cells, A. delicatissima W. & G. S. West, occurred at the same time but were never as abundant. Aphanotheca: Colonies of an undetermined species belonging to this genus were quite common in the plankton collections in the fall of 1926. Chroococcus: Three species of Chroococcus occurred in the recent collec- tions. Probably because of the small size of the colonies, none of this genus were found in the earlier collections. Colonies of C. dispersus (V. Keiss.) Lemm. were found occasionally in the 1926-1927 collections. C. minutus (Kutz.) Nag. and C. limneticus Lemm. occurred sparingly in the 1926 collections. Snow reported the latter species and also C. pallidus Ebr. and C. purpureus Snow from Lake Erie. Anabaena: Filaments of a very small undetermined species of Anabaena occurred sparingly in some of the collections of Dec. 1887, Sept. 1888, Oct. 1888, Oct. 1926, and May 1927. It was never abundant and was probably lost through the meshes of the net in many of the collections. A. circinalis (Kutz.) Rab. was common (300,000 per c. m.) in the silk-net collections July 10, 1927 at Chicago. Snow reported this species from Lake Erie. Ward recorded A. flos-aquae Kg. from the Traverse Bay region. Lyngbia: An undetermined species of Lyngbia occurred abundantly in a!l the 1927 collections. This form was found sparingly in the collections of Oct. 1888. Snow found L. wollei Farlow in Lake Erie. Oe — THE PLANKTON OF LAKE MICHIGAN 219 Oscillatoria: A few strands of Oscillatoria princeps Vaucher occurred in the collections of Oct. 1888. Snow recorded a number of species from Lake Erie but not this same species. BACELLARIACEAE (DIATOMS) Diatoms are the most abundant organisms in the plankton of Lake Michigan. Every collection contained them in large numbers. Twenty- six species, chiefly of four genera, were noted in all. Thomas and Chase (1886) collected 215 species of diatoms during a period of sixteen years from the water supply of Chicago, many of which undoubtedly were not plankton diatoms. Thompson (Ward, 1896) found diatoms very abundant at Traverse Bay and listed fourteen species. Whipple (Leigh- ton, 1907) gave eight genera as being common in Lake Michigan at Chi- cago. Lysigonium (Melosira): Lysigonium varians Ag. was common in all the collections examined. JL. granulata (Ehr.) Ralfs. occurred occasionally, and a species of this genus resembling L. arenaria Moore was abundant in the Oc- tober 1926 collections. Snow reported Melosira arenaria Moore, M. granulata (Bhr.) Ralfs., and M. varians Ag. from Lake Erie; but neither Whipple nor Ward reported any species of this genus. Cyclotella: A species of Cyclotella resembling C. meneghiniana Rabh. was common (2,500-1,760,000 per ec. m.) in the collections of 1926 and 1927. This small diatom occurred sparingly in the 1887-1888 collections. Snow reported four species of Cyclotella from Lake Erie. Ward listed C. operculata K. from the Traverse Bay region. Whipple found this genus abundant at Chicago. Stephanodiscus: Stephanodiscus niagarae Ehr. occurred occasionally in most of the collections and was abundant in the 1927 collections, reaching a maximum of 500,000 per c. m. in a filter-paper collection May 14, 1927 at Dunes Park. Snow found S. niagarae in Lake Erie. Ward reported this species from Traverse Bay, but Whipple listed it as absent from Lake Michigan at Chicago. Striatella (Tabellaria): Striatella fenestrata (Kutz.) Kuntze was one of the most abundant organisms in the plankton, reaching a maximum of 143,000,000 per c. m. May 14, 1927 at Dunes Park. Every collection throughout the year of 1887-1888 was filled with the zigzag chains of this diatom. S. flocullosa (Roth.) Kuntze was plentiful in most of the collections but never as abundant as S. fenestrata. Thompson found both species abundant in the Tra- verse Bay region, Snow reported them from Lake Erie, and Thomas and Chase found them in the Chicago water supply. Whipple listed this genus as abundant in Lake Michigan at Chicago. Fragilaria: Fragilaria virescens Ralfs. and F. crotonensis (Edw.) Kitton were abundant at all times. The ribbon-like strands of these diatoms, together with Striatella, Synedra, and Asterionella, composed most of the plankton. The most abundant of all the organisms in the plankton was F’. crotonensis, which reached a maximum of 384,000,000 per ec. m. in a silk-net collection July 10, 1927 at Chicago. Thompson reported fF’. capucina Desm. as very common in Traverse Bay. Snow listed F. crotonensis and F. virescens from Lake Erie. Whipple found this genus only occasionally in Lake Michigan at Chicago. Chase and Thomas reported six species of this genus, including F. virescens but not F. crotonensis, from the Chicago water supply. 220 ILtinors NATURAL History SurvEY BULLETIN Synedra: Synedra ulna (Nitzsch.) Ehr. and Synedra tenwissima Ehr. were abundant in all collections. S. wlna, one of the most abundant, reached a maxi- mum of 176,000,000 per c. m. May 14, 1927 at Dunes Park, while S. tenwissima, although never so abundant, reached a maximum of 24,000,000 on the same date. Both species appeared to flourish more abundantly in the spring and late fall than in other seasons. Thompson reported S. ulna and S. affinis Kutz. in Traverse Bay. Snow reported S. wlna and S. oxyrhynchus Kg. from Lake Erie. Thomas and Chase listed fourteen species of this genus Including S. ulna but not 8S. tenuissima from the Chicago water supply. Asterionella: Asterionella gracillima (Hantzsch.} Heib., one of the most common diatoms, occurred in all collections except those of June and July, 1888. Its occurrence throughout the rest of the year suggests that it has a longer season of growth in Lake Michigan than in other nearby waters, pos- sibly because of the lower temperatures of Lake Michigan. Kofoid (1908) reported this species as a spring form in Illinois River with a maximum abundance of 891,000,000 per c. m. The greatest abundance observed in Lake Michigan was 100,000,000 May 14, 1927 in a filter-paper collection at Dunes Park. Thompson reported A. formosa Hass. from Traverse Bay. Snow also listed A. formosa from Lake Erie. Whipple found Asterionella to be the most abundant genus at Chicago. Chase and Thomas listed A. formosa from the Chicago water supply. Navicula: Several undetermined species of Navicula occurred very spar- ingly in the collections of 1927. Diatoms of this genus never appeared in any quantity in any of the collections. Ward listed three species of Navicula from Traverse Bay, and Whipple found Navicula to be common at Chicago. Snow recorded three species from Lake Erie. Forty-nine species of this genus were listed by Thomas and Chase from the Chicago water supply, but many of them undoubtedly were not plankton species. Cocconeis! Cocconeis placentula Ehr. was found rather sparingly May 1888 at Chicago and May 1927 at Dunes Park. This species reached a maximum abundance of 100,000 per c. m. in the filter-paper collections. Snow recorded this species from Lake Erie. Ward found C.. transversalis Greg. in Traverse Bay. Thompson reported (. placentula as being dredged from the bottom of . Trave-se Bay. Thomas and Chase listed C. lineata K. and C. pediculus Ehr. from the Chicago water supply. Gyrosigma (Pleurosigma): Gyrosigma acuminata (Kutz.) Cl. was found sparingly at Dunes Park, May 14, 1927, but was not observed in any other collections. G. attenuatum Sm. was reported by Snow from Lake Erie but was not among the six species of this genus listed by Thomas and Chase from the Chicago water supply. Amphiprora: Amphiprora ornata Bailey occurred (300,000 per c.m.) in the filter-paper collections May 15, 1927 at Dunes Park and also (48,000) in the silk-net collections July 10, 1927 at Chicago. A. alata (Ehr.) Kutz. was found sparingly in the collections made Oct. 17-18, 1926. These species have not been reported by other workers in any of the Great Lakes except by Thomas and Chase who reported A. caluwmetica Thomas and A. ornata from the Chicago water supply. Gomphonema: Gomphonema acuminatum Ehr., which occurred very spar- ingly in the silk-net collections at Dunes Park May 14, 1927, was quite com- mon in the 1887-1888 collections except during the months of June, July, and December. It usually appeared in swarms attached to floating debris. Snow reported this species and three others from Lake Erie.’ Thomas and Chase listed eighteen species including G. acuminatum from the Chicago water supply. ee THE PLANKTON oF LAKE MICHIGAN 221 Cymbella: Cymbella lanceolata (Ehr.) Kirchn. occurred sparingly in the silk-net collections May 14-15, 1927 at Dunes Park but did not appear in any of the other collections. Snow reported C. maculata Kg. and C. rotundata H. H. C. from Lake Erie. Thompson found @. gastroides to be common in the Traverse Bay region. Thomas and Chase reported twelve species including C. lanceolata from the Chicago water supply. Encyonema: Encyonema prostratum (Berk.) Kutz. occurred in the filter- paper collections (1,400,000 per c. m. May 14, 1927) at Dunes Park. This species appeared in collections of Nov. 1887 and Oct. 1888, apparently having Thomas and Chase found it and three others of this genus in the Chicago a fall and spring distribution. Snow reported this species from Lake Erie. water supply. Cystopleura: Cystoplewra turgida (Ehr.) Kuntze occurred frequently in the collections May 14-15, 1927 from Dunes Park. An undetermined species of this genus also occurred rather sparingly in the same collections. No species of this genus were observed in any other collections. Snow reported Cysto- pleura (Epithemia) turgida and three other species of this genus from Lake Erie. Thomas and Chase listed six species of this genus including (. turgida from the Chicago water supply. Homoeocladia: Homoeocladia sigmoidea (Nitz.) Elmore was found spar- ingly in some of the collections May 14, 1927 from Dunes Park, but did not ap- pear in any of the other collections. Snow reported this species as Nitzschia sigmoidea (Nitzsch.) Sm. and another species, N. linearis Sm., from Lake Erie. Thompson recorded N. sigmoidea from Traverse Bay. Whipple listed diatoms belonging to Niteschia as being very abundant at Chicago. Thomas and Chase found eleven species of this genus including N. sigmoidea in the Chicago water supply. Sphinctecystis: Sphinctocystis eliptica (Kutz.) Kuntze occurred sparingly in the 1926-1927 collections. It was found only once (in June) in the collections of 1888. S. librilis (Ehr.) Hass. was present in small numbers in most of the 1887-1888 collections, not appearing from Dec. to April, and in most of the 1926-1927 collections. Snow reported S. (Cymatopleura) eliptica Sm. and S. solea Breb. from Lake Erie. Thomas and Chase listed five species of Cyma- topleura, including C. eliptica but not C. librilis, from the Chicago water supply. Surirella: Surirella robusta Ehr. occurred very sparingly (85 per c. m.) July 10, 1927 at Chicago. Snow recorded three species of this genus but not this species from Lake Erie. Thomas and Chase listed 10 species of this genus but not robusta from Lake Michigan at Chicago. Campylodiscus: Campylodiscus hibernicus Ehr. was found in very small numbers in one silk-net collection from Dunes Park, May 14, 1927. Snow re- ported C. cribrosus Sm. from Lake Erie. Thomas and Chase listed C. hibernicus and C. noricus Ehr. from the Chicago water supply. CHLOROPHYCEAE (GREEN ALGAE) The green algae were never abundant in the plankton of Lake Michi- gan. Twenty species, some of which were very rare, occurred in the col- lections. Many of the smaller species which occurred rarely in the recent series did not appear in the earlier series; this may have been due to the use of a coarser net through which most of the smaller forms were lost. Snow (1902) recorded 126 species from Lake Erie. Thompson (Ward, 222 ILLinoris NaturaL Hisrory SurvEY BULLETIN 1896) reported that the green algae were almost entirely absent from the Traverse Bay region, as he found only a few species there. Whipple (Leighton, 1907) listed seven genera as common in Lake Michigan at Chicago. Closterium: Closteriwm gracile Breb., which occurred sparingly in most of the recent collections, was not observed in any of the 1887-1888 collections. C. moniliferum (Bory) Ehr. occurred only in the July 1927 collections (80 per c.m.). Snow noted six species of this genus from Lake Erie but did not include gracile and monoliferum. Whipple reported Closteriwm as occurring occasion- ally in Lake Michigan at Chicago. Spirogyra: Fragments of Spirogyra (several unidentified species) were found occasionally in the 1927 collections and in the collections of April and June 1888. This genus was not reported by Snow or Thompson, although it was noted by Whipple as ‘occasional’ at Chicago especially around the water sup- ply crib. Cosmarium: An undetermined species of Cosmariwm was found only in the filter-paper collections May 14, 1927 at Dunes Park (27,000 per c.m.). This species may have been lost through the meshes in the silk-net collections. Snow listed eleven species of Cosmarium from Lake Erie. Chrysophaerella: Some colonies of green algae agreeing with Chrysophae- rella longispina Lauterborn were quite common in the collections Oct. 17-18, 1926 at Michigan City and Sawyer and July 10, 1927 at Chicago. This species did not appear in any of the other collections and was not reported from the Great Lakes by any of the previous investigators. Dictyosphaerium: Colonies of Dictyosphaerium puchellum Wood were quite common in all of the 1926-1927 collections. The greatest abundance recorded was 112,000 colonies per c. m. in a silk-net collection July 10, 1927 at Chicago. This species occurred in small numbers in the collections of August 1888. Snow reported D. puchellum and D. ehrenbergianum Nag. from Lake Erie. Botryococcus: Colonies of Botryococcus sudeticus Lemm. occurred in small numbers in the collections of Oct. 17-18, 1926. Snow listed only B. braunii Kg. from Lake Erie. Kirchneriella: A few species of Kirchneriella obesa Schmidle occurred sparingly (200 per c. m.) in the collections Oct. 15, 1926 from Michigan City. Snow reported this species and K. lunaris (Kirch.) Mob. from Lake Erie. Oocystis: An undetermined species of Oocystis occurred rarely in the collections, 200 per c. m. Oct. 18, 1926 at Sawyer and 30,000 per c. m. May 14, 1927 at Dunes Park. Snow reported three species of this genus from Lake Erie. Sphaerocystis: A few colonies (845 per c. m.) of Sphaerocystis schroeteri Chodat were found in a silk-net collection May 14, 1927 at Gary and also (7,000 per c. m.) July 10, 1927 at Chicago. This species has not been reported for the Great Lakes by any of the other investigators. Ankistrodesmus: 1 (Ok 4.7 3 (Check 66.6 | 66.6 On Apple 3% 1.5% 4 Soluble oil No. 90'Soap No. 15)Unsat. | 9.0 83 1.0 0.2 4.9 5 Soluble oil No. 17\Soap No. 15 Unsat. | 9.0 83 1.0 0.6 L5 6 Soluble oil No. 16 Soap No. 15 Sat. 0.0 83 0.2 0.4 0.0 7 Check | 40.0 | 40.0 On Peach 3% 2% 8 (Stock Emul. No. Inert Unsat. 9.0 83 | 1.0 L7 26 210 9 jStock Emul. No. Inert Sat. 0.0 83 9.2 0.6 ales} 200 | 10 |Check | 12.6 | 12.6 Note: Emulsifying agent in Sol. oil No. 17, reduced. death. It has been observed by deOng (’27) that scale insects may act- ually expel the lighter oils from their tracheal systems. If the action were mainly chemical, the unsaturated oils, which are more active chemically, would be more effective. The important point in scale control is to apply an emulsion that will release quickly an oil of sufficiently high viscosity and low volatility to give a residue that will persist for sometime. InyuRY TO PEANTS As a general rule, the higher the viscosity and the lower the volatil- ity of an oil, the more likely it is to cause injury to plants, whether it is saturated or unsaturated. It is quite possible to apply a volatile, unsatu- rated kerosene without much danger of injury, but with oils that give a persistent residue it is necessary to increase the degree of refinement in 254 ILLINoIs NATuRAL History Survey BULLETIN order to insure safety to foliage. Wherever a persistent residue is required, therefore, the difference between saturated and unsaturated oils is the most important consideration with respect to plant injury. In tests on apple foliage it has not been found necessary to use an oil of medicinal quality, i. e., an oil that shows no loss to 97 per cent sulfuric acid. An oil having a loss of 1 per cent to sulfuric acid and a viscosity of 83 has been found quite safe on apple foliage at dilutions as high as 4 per cent when emulsified with some inert material. But the incorpora- tion of a saturated oil, even of medicinal quality, in a soluble oil did not prove safe, nor did it apparently decrease the injury below that of the corresponding unsaturated oil. Although the saturated oil itself and the petroleum soap were relatively innocuous when applied separately, a safe combination of the two could not be worked out. Replacing sodium with potassium in the soap did not reduce injury; neither did an entire change of emulsifying agent. The incorporation of a highly volatile saturated oil in a soluble oil did reduce injury considerably, but the combination was not entirely safe and was not of satisfactory insecticidal efficiency. (Tables VIII, IX, X.) In the early stages of the work, various oils were applied undiluted, or “straight”, to apple twigs in order to determine their liability to cause injury. The results of a typical test are seen in Table XIII. TABLE XIII. InguRY TO APPLE FOLIAGE BY UNDILUTED OILS. Viscos- Vola- Loss to | Estimated per cent injury observed after Item ity tility | H.SO, ie Percent| Sec. Per cent | 20 hrs. | 25 hrs. | 2 da. | 4 da. | 6 da. |10 da. 1 32 35.1% 0.0 0 0 0 0 0 0 2 83 1.0 0 0 0 0 0 10* 3 83 0.2% 0.0 0 0 0 0 0 10* 4 32 54.3% 3.0 0 0 0 0 0 0 5 83 1.0% 9.0 0 40 80 90 100 | 100 6 104 0.2% 7.0 0 40 80 90 100 | 100 * Finally, yellowing and defoliation. Tests of this kind illustrate strikingly the acute injury done by un- saturated oils. Twigs treated with unsaturated oils show almost com- plete blackening of the tissue within 48 hours, while it may be several days before the saturated oils cause injury, and even then the injury is not “burning” but “yellowing” and defoliation. The latter seems to be the result of suffocation of the cells in the tissue, while the action of the un- saturated oils appears to be chemical for the most part. The very vola- tile oils leave the plant without causing injury. The important point in selecting an oil emulsion for spraying foliage is to use one that is as near- ly inert chemically as possible. Such an emulsion is obtained with a satu- rated oil and an inert emulsifier. This conclusion is in harmony with deOng’s. ee ee ee a ye oa a Some PROPERTIES OF O1L EMULSIONS 255 CONCLUSIONS Emulsifying agents used in making oil emulsions for spray purposes vary in wetting ability, as measured by Stellwaag’s angle-of-contact method, and consequently cause variations in the effectiveness of the emul- sions. This is especially important in the control of aphids. The stability of oil emulsions, which is indicated to some extent by the size of the globules, is one of the principal factors in insecticidal ef- ficiency. The type of oil emulsified, the kind and amount of emulsifying agent, the quality of water used for dilution, and other factors commonly considered unimportant, are capable of causing changes in stability and consequent fluctuations in efficiency. Increased effectiveness may or may not be accompanied by an in- crease in the size of globules. Increased size ot globules is the result of desirable qualities in an emulsion rather than the cause of effectiveness. For use against aphids, the most effective emulsion is one that has high wetting ability coupled with instability. Either of these factors may vary so as to be dominant. A relatively “poor-wetting”, unstable emul- sion may be more effective on aphids than a “‘good-wetting’’, stable emul- sion. If the stability of two emulsions is about the same, then the one with the greater wetting ability is the more effective on aphids. In the control of scale insects, the instability of the emulsion is the primary consideration. The less stable the emulsion, the greater its ef- ficiency. High wetting ability is not necessary for the control of San Jose scale and oyster-shell scale, because of the comparative ease with which their host plants are wetted. The emulsions used for the control of these insects should release quickly an oil of sufficiently high viscosity and low volatility to give a persistent residue. A saturated oil, because of its influence in some cases on the stabil- ity of the emulsion, may be more effective than an unsaturated oil. The amount of oil adhering and taking proper effect on the insect is dependent upon both the wetting ability and the instability of the emul- sion. Inadequate wetting is a common cause of inefficiency, but excessive wetting, which results in some of the emulsion running off from objects that are easily wetted, is also a possible cause of inefficiency. These con- ditions are dependent on the kind of emulsion and the insect involved. In order to be innocuous to plant foliage, an emulsion should be as inert chemically as possible. Soaps and unsaturated oils tend to injure foliage. Each oil emulsion should be considered as a particular individual in- secticide, having properties peculiar to itself and giving results that other emulsions may not. 256 Ittinois NarurAL History SurRVEY BULLETIN ACKNOWLEDGMENTS The writer hereby expresses his gratitude to Mr. W. P. Flint, of the Illinois State Natural History Survey, for arranging many of the experi- ments and for suggestions and assistance from time to time; to Dr. B. A. Porter, of the U. S. Bureau of Entomology, for assistance, particularly with the San Jose scale experiments; and to Dr. W. A. Ruth, of the Hor- ticultural Department of the University of Illinois, for the use of equip- ment and orchards, and for most friendly cooperation in every way. For a careful criticism of the manuscript, the writer is grateful to Dr. F. W. Sullivan and Dr. E. W. Adams of the Standard Oil Company (Indiana). Thanks are due, also, to these chemists and other members of the Technical Department of the Standard Oil Company for assistance and cooperation at all times. Most of the emulsions used in the various experiments were prepared by the laboratories of the Standard Oil Com- pany. BIBLIOGRAPHY AvAM, Nett K., and Jessop, GILBERT 1925. Angles of contact and polarity of solid surfaces. Jour. Chem. Soc. 127: 1863-1868. CHANDLER, S. C., Firnt, W. P., and Huser, L. L. 1926. Recent insecticide experiments in Illinois with lubricating oil emulsions. J1I. State Nat. Hist. Surv. Bull. 16: 103-126. Cooper, W. F., and Nutrrarr, W. H. 1915. The theory of wetting, and the determination of the wetting power of dipping and spraying fluids containing a soap basis. Jour. Agr. Sc. 7: 219-239. DEONG, E. R. 1926. Technical aspects of petroleum oils and oil sprays. Jour. Econ. Ent. 19: 733-745. DEONG, E. R., KnicHT, H., and CHAMBERLIN, J. C. 1927. A preliminary study of petroleum oil as an insecticide for citrus trees. Hilgardia, Calif. Agr. Hxp. Sta. 2: 351-383. KLINT, W. P., and Biccrr, J. H. 1926. The fruit-tree leaf roller and its control under Illinois conditions. Ill. State Nat. Hist. Surv. Ent. Circ. 9. FREUNDLICH, H. 1922. Colloid and capillary chemistry. Translation by Hatfield from the third German edition. Pub. by E. P. Dutton Co., New York. Grirrin, E. L., RicHArpDSOoN, C. H., and BuRDETTE, C. 1927. Relation of size of oil drops to toxicity of petroleum oil emulsions to aphids. Jour. Agr. Res. 34: 727-738. HARKINS, W. D., Daviss, E. C. H., and CLark, G. L. 1917. The orientation of molecules in the surface of liquids, ete. Jowr. Amer. Chem. Soc. 39: 541-96. SoME PROPERTIES OF OrL EMULSIONS bo or “1 Haw tey, I. M. 1926. The fruit-tree leaf roller and its control by oil sprays. Utah Agr. Exp. Sta. Bull. 196. List, G. M. 1924. The oyster-shell scale. 16th Ann. Rept. of the State Entomologist of Colo., 25-31. Metanper, A. L., SpuLer, A., and GREEN, E. L. 1924. Oil sprays—their preparation and use for insect control. Wash. Agr. Exp. Sta. Bull. 184. Moore, W., and Grauam, S. A. 1918. Physical properties governing the efficacy of contact insecticides. Jour. Agr. Res. 13: 523-537. Moore, W. 1921. The spreading and adherence of arsenical sprays. Univ. Minn. Tech. Bull. 2. 1923. The need of chemistry for the student of entomology. Jour. Econ. Ent. 16: 172-176. NuTTALL, W. H. 1920. Wetting power and its relation to industry. Jour. Soc. Chem. Ind. 39: 67-77. Ropinson, R. H. 1925. Spreaders for spray materials, and the relation of surface tension of solutions to their spreading qualities. Jour. Agr. Res. 31: 71-81. Rutu, W. A. and Ketter, V. W. 1922. Recent advances in spraying. Trans. Ill. Hort. Soc. (n. s.) 56: 90-103. Smiru, Loren B. 1916. Relationship between wetting power and efficiency of nicotine- sulphate and fish-oil-soap sprays. Jour. Agr. Res. 7: 389-399. STELLWAAG, F. 1924. Die Benetzungsfahigkeit fliissiger Pflanzenschutzmittel und ihre direckte Messbarkeit nach einem neuen Verfahren. Zeits. Angew. Ent. 10: 163-176. Surtman, H. L. 1920. A contribution to the study of flotation. Trans. Inst. Min. Met. (London) 29: 44-208. TRAPPMANN, W. 1926. Methoden zur Priifung von Pflanzenschutzmitteln. I. Benetz- ungsfahigkeit. Arb. Biol. Anst. 14: 259-266. WAKELAND, CLAUDE. 1925. The fruit-tree leaf roller—its control in Southern Idaho by the use of oil emulsion sprays. Jdaho Agr. Exp. Sta. Bull. 137. Woerrm, R. S. 1925. The value of sprays and fumigation for resistant black scale con- trol. Bull. Calif. Fruit Growers Exch. (Los Angeles). 258 Inninors NaturAL History SuRVEY BULLETIN Woopman, R. M. 1924. The physics of spray liquids. I. The properties of wetting and spreading. Jour. Pom. Hort. Sci. 4: 38-58. YorHeErRS, W. W. 1924. Mixing emulsified mineral lubricating oils with deep-well waters and lime-sulphur solutions. U. S. Dept. Agr. Dept. Bull. 1217. Appendix A DEFINITIONS OF TERMS A saturated hydrocarbon is a compound of hydrogen and carbon in which the normal valence of carbon (four) is entirely satisfied. H H | Example: ethane H— C——C—H | | H H An unsaturated hydrocarbon is one in which the normal valence of carbon is not satisfied; hence, the compound is more active chemically than a saturated hydrocarbon. H H | | Example: ethylene C——— 1 | H H A saturated oil, or white oil, is one from which the unsaturated hydrocar- bons have been removed by treatment with sulfuric acid. A saturated oil is practically inert chemically. An unsaturated oil is not as highly refined as the white oils. While an oil of this kind may consist largely of saturated hydrocarbons, not all the un- saturated hydrocarbons have been removed in refining it. Loss to Sulfuric Acid.* The loss in volume of an oil as a result of treat- ment with sulfuric acid is an index to the unsaturated hydrocarbon content. The greater the loss, the more unsaturated the oil. There is a standard method of procedure for this test. Viscosity.* This is simply defined as resistance to flow, or negative fluidity. The standard of comparison used for oils is the Saybolt test. The units used are seconds, and they represent the time required for a given volume of oil to flow through a given orifice at a definite temperature. Volatility; This is an arbitrary test which expresses as per cent by weight, the evaporation of a given quantity of oil at 212°F for 8 hours. “Soluble Oil’ and “Stock Emulsion”. For purposes of discussion, a dis- tinction is usually made between “soluble oil’ and “stock emulsion’, although there is no basic difference between them, both being oil emulsions. ‘Soluble oils,’ which are more or less transparent because of the extremely fine degree of dispersion of the oil phase, are compounded petroleum products which form milky-white emulsions when diluted with water. Dendrol and Sunoco are examples. The term “stock emulsion” is used with reference to a concentrated emulsion, such as Volck, Sherwin-Williams Free-mulsion, homemade lubricating oil emulsion, ete. * The determinations of loss to sulfuric acid and of viscosity were made by the Standard Oil Company (Indiana), according to United States Government Specifi- cations for Lubricants and Liquid Fuels and Methods of Testing, U. S. Bureau of Mines, Technical Paper 323 A., March 18, 1924. + Refer to British Engineering Standards Association, Tentative British Stand- ard Specifications 148 (1923), pages 9-10, Section 14. a SoME PROPERTIES OF OIL EMULSIONS 259 Appendix B EXPERIMENTAL METHODS Tests on aphids. Aphis pomi De G. was obtained on the water sprouts of apple; Aphis spiraecola Patch on Spiraea vanhouttei Zabel; Hesteroneura setariae Thos. on a grass (Hchinichloa crus-galli L.); and Tritogenaphis am- brosiae Thos. on wild lettuce (Lactuca canadensis L.). The infested shoots were cut from the plants a short time before spraying. Nearly all the leaves were removed so that the aphids would not be protected. The shoots were then placed vertically on a revolving stand and sprayed thoroughly with a hand sprayer having bottom feed. An excessive amount of spray on the aphids was insured, i. e., as much as would adhere. After treatment, the shoots were inserted in holes in the tops of pill boxes filled with water and isolated on squares of paper bordered with tree tanglefoot. After approximately 24 hours, the aphids were carefully removed with a camel’s hair brush and counted. Tests on oyster-shell scale. For the laboratory tests with oyster-shell scale, Lepidosaphes ulmi Linn., infested poplar (Populus deltoides Marsh) twigs were used. These were trimmed uniformly, and all scales were removed except 25 to 50, the number varying with separate experiments, but never within one experiment. Five of these twigs were treated with each material, and several untreated checks of five twigs each were carried through each experiment. After treatment, the twigs were placed in a moist sand bench to grow. A ring of tanglefoot around each prevented the escape of “crawlers” at the time of hatching. Throughout the hatching period, the twigs were examined daily with a binocular microscope, and the crawlers were removed as counted. The checks usually hatched very uniformly, and the hatch on the treated blocks was calculated to ‘check basis’. About 3,000 to 3,500 eggs hatched from each check block of five twigs. Tests on San Jose scale. All of the tests of sprays on San Jose scale (Aspidiotus perniciosus Comstock) were conducted in the field. In some cases, large infested branches were treated; in others, several entire trees were used . in each block. The usual procedure of taking San Jose scale data was followed. A month or six weeks after treatment, twigs were collected from the various blocks, and a count of 1,000 scales was made to determine the percentage of survival. In making the counts, the scale was turned over in order that the insect itself might be seen. Robust, lemon-colored ones were recorded as “alive”. Brown, black, shriveled, or “off color’ ones were recorded as “dead.” Appendix C ANALYSIS OF TAP WATER USED IN EXPERIMENTS Illinois State Water Survey, Sample No. 51728, June 28, 1924 Determinations Parts per million POM accra crsiet are wears Boop o ea HIG eye sn niche eee eens 1.2 IMAI PAN ESE 22 yee says areteieress WOR Dts teeta ten ee aoe 0.0 SHGTCr i pom eto oc aac eers SIOD be tofatepesereseceetout ate 14.1 IN OM Olatil ects acieraitve tro tanslel stems icteyeaie akareiouelscevalcrersles 1.8 PANITINNATN Boye, one Seevwieleusyereneiejelenern) ace Lois. 2 oie syste oraiinse 0.0 Gale rcrcicca mics ers eetei LOR Wei teins erie ces 66.9 WEVaTERT ENG Poe SooceqcaqoRooue 1 (ee ep ae eae 31.4 PUNT TIA OVI seine whe salons yciecete aiats INE itcsssccis verter 5.3 SRO TUM ca cist che ee Nov icifararayer'ahere INE, het isto anton temere 34.8 IPOUASSIUI etic tenates, syetsnaisisl sis RGAE See rats oer aise 4.1 RSET UC encore et ahe case tears oie: » | J Q “| 1 & O H u 1 8S 304, \ Fl 192 a on0 | by d .y oO Si | zo4kln | | eee ee jou O O Q O ye Ny Le “A o © 0489 a pes a ——* - / 4 U / a 2 3 10 20 lo 20 30 is id | | April May June July o-oo Plum Curculio Tarnished Plant Bug Fic.5. Graphs showing numbers of Tarnished Plant Bug and Plum Curculio caught on sheets by early-morning jarring of 10 unsprayed peach trees, Carbondale, Illinois. The jarring was done between 6:00 and 7:00 a.m. The insects were turned loose after counting, in order to keep conditions as near natural as possible. SomMeE CAUSES OF CAT-FACING IN PEACHES Fic. 6. Peaches injured in cages by three kinds of stink bugs: top row, Buschistus servus. Vincennes, Indiana. anese Beetle Laboratory. variolarius; middle row, E. tristigmus; bottom row, EB. 1927. Photos by R. L. Coffin, of Jap- 268 Itninoris NarurAL History SurRvVeEY BULLETIN Stink Bucs Four species of stink bugs* produce cat-facing. (See Figures 3 and 6.) These large, angular bugs, gray to brown in color, are often very abundant in peach orchards in spring, and we have observed them re- peatedly in the act of feeding on small peaches. When the peaches are very small, most of the injured ones shrivel and drop, but when the peaches are larger, most of those that have been fed upon remain on the tree and become distorted or cat-faced. The stink bugs continue to pro- duce cat-facing for five or six weeks after petal fall, or until the peaches become an inch or more in diameter. Feeding continues after this stage of development, in diminishing amounts, and the lesions produced later are less extensive. Two of the species involved, E. variolarius and E. tristigmus, were very abundant during 1927 in southern Indiana, and the Fic. 7. Colony of small stink bugs, clustered on leaf near egg mass from which they hatched. Vincennes, Indiana. 1927. (About six times natural size.) other two species mentioned were probably responsible for very little of the cat-facing there in that season. A few of the stink bugs lay eggs in small groups on the leaves of the peach trees. The egg masses observed have usually been in multiples of seven, fourteen being the most common number. On hatching, the young bugs remain clustered around the egg mass for a few days until they un- dergo the first molt (see Figure 7) ; they then disperse and feed for a short time on the leaves and on the young peaches, if they find any nearby. + Buschistus variolarius (Palisot de Beauvois); H. euschistoides (Vollenhoven) ; BE. servus (Say); and £#. tristigmus (Say). These are the more common members of this genus in southern Illinois and southern Indiana. Some CAUSES OF CAT-FACING IN PEACHES 269 Their feeding may cause slight dimples on the fruit, out of which ooze small quantities of gum; this ‘kind of injury, however, is not very common, since the small bugs disappear from the peach trees soon after the first molt. They are found in abundance on weeds in the orchard in early sum- mer, particularly on the young plants of one of the fleabanes, Erigeron canadensis L. Later on, bugs of all ages may be found in large numbers in fields of soy beans and cow peas. In 1927, one of the stink bugs (E. variolarius) was found in large numbers in red clover fields. They may be found, however, to a greater or lesser extent on almost any grow- ing plant. Stink bugs are said to pass usually through two generations during a season, and they hibernate in the adult stage. CURCULIO The Plum Curculio, Conotrachelus nenuphar Herbst, so well known to all peach growers, produced cat-facing on peaches in our cages. The Fie. 8. Peach injured in cage by Fic. 9. Curculio ovipositing on a curculio. Carbondale, Illinois. peach. (About four times nat- 1926. ural size.) work of this insect is best known to the growers by the dropping of peaches early in the season and the occurrence of wormy fruit at harvest. When the injured fruit remains on the tree, it is more or less distorted. (See Figures 8 and 9.) OTHER POSSIBLE CAUSES While we are confident that the list of insects already named includes the important causes of cat-facing in southern Illinois and southern In- diana, it is probable that further investigations will show that other in- sects are also capable of producing cat-facing. 270 ILninois Narurat History SuRVEY BULLETIN The Green Soldier Bug, Acrosternum hilare (Say), one of the largest of the stink bugs, is occasionally seen in peach orchards, and its young stages sometimes cause considerable injury to the fruit! in the form of numerous small dimples (see Figure 10). None of the mature bugs have been available for caging tests in spring. A few peaches may be cat- faced by this species, but it is so scarce in the peach orchards of this section that it cannot be an important factor. A species of thrips, Frankliniclla tritici (Fitch), which is often pres- ent in large numbers in the peach blossoms and around the small fruit, was at first suspected as the cause of cat-facing, but we have been unable to connect this insect with the trouble. In one season in particular (1925) thrips were very abundant in our cages (they are so very small that they can pass through the ordinary screen cage), but no sign of injury ap- peared until other insects were introduced. Even when the normal popu- lation was augmented by the addition of fifteen to twenty thrips to each Fic. 10. Peaches injured by young of Green Soldier Bug, Acrosternum hilare (Say). Vincennes, Indiana, 1927. Photo by R. L. Coffin, of Japanese Beetle Laboratory. peach, no injury appeared. Field observations and counts have failed to show any relation between thrips abundance and amount of cat-facing. The fruit in some orchards in which thrips have been almost entirely ab- sent has suffered severe cat-facing. As a result of these studies, we believe that the work of thrips is a negligible factor. RELATIVE IMPORTANCE OF THE DIFFERENT INSECTS We can make no definite statement at present that will hold true for every year, or in every peach section, or even in all parts of the same section, as to the relative importance of the different species implicated in i 4Whitmarsh, R. D., 1917. The Green Soldier Bug. Ohio Agr. Exp. Sta. Bull. 310. SoMkE CAUSES OF CAT-FACING IN PEACHES 271 producing cat-facing. The curculio is probably of less importance in this respect than the sucking bugs—a belief which is supported by the fact that serious cat-facing injury occurs in some peach orchards in the Pacific Northwest where the ctirculio does not occur. If it were possible to distinguish the injury caused by each of the dif- ferent insects, it could be determined which insect is of the greatest im- portance in individual orchards. Although the different imjuries when fresh may be identified with some degree of certainty, they cannot be dis- tinguished cne from another after they have healed over. Host PLrant RELATIONS With the exception of the Plum Curculio, which is probably a lesser factor, the insects involved in this problem do not breed to any extent on peach. They are very general feeders, and may be found on any one of a long list of food plants. The Tarnished Plant Bug seems to favor plants in the family Compositae, especially the daisies, the fle: abanes, and the wild asters. It also breeds freely on the legumes, but may be found on almost any other plant.° The stink bugs are, likewise, very general feeders and may be found “on a great many ‘different kinds of Fine Among their preferred host plants may be mentioned red clover, cow peas, and soy beans. The pres- ence of these bugs on peach fruit in the spring is merely incidental and in no way essential to their life cycle. The plant relationships of the Plum Curculio are not as extensive as those of the other insects involved. Of the cultivated plants aside from peach, the curculio feeds regularly on apple, plum, cherry and other fruits, which are often planted close to peach orchards. Of the wild host plants, wild haw and wild plum are probably the most important. HIBERNATION OF THE TARNISHED PLANT BuG Studies were made of the hibernating habits of the Tarnished Plant Bug in an effort to discover some means of controlling this cause of cat- facing. The bugs were found in a variety of winter habitats; some in clumps of clover and alfalfa in fields where numbers of them had been observed to be feeding in late summer and autumn; some under fallen leaves of trees at the edges of these fields; a few in apple orchards under various kinds of cover, such as grass, leaves, and bits of bark; and a few in other places wherever there was sufficient cover, The woolly leaves of mullein seem to be the most favored winter quarters in this section of the country, for the bugs are usually to be found in mullein even when difficult to find elsewhere. As many as fifty of them have been found at one time in a single plant. The highest average found in any one peach district was eighteen bugs per plant. Many Tarnished Plant Bugs do not go into true hibernation, but leave their winter quarters on warm days. Counts made on November *For a detailed discussion of host plants of the Tarnished Plant Bug, see Cornell Bulletin No. 346, “The Tarnished Plant Bug’, pages 467-472, by C. R. Crosby and M. D. Leonard, 1914. 272 ILtinois NATURAL History SURVEY BULLETIN 27, 1926, near Carbondale, Illinois, showed an average of five bugs per square foot under hickory leaves at the edge of a sweet clover field. Counts made nine days later, in exactly the same places, after several mild* days had intervened, showed an average of only one bug in five square feet. On three occasions all the hibernating bugs were removed from certain mullein plants in an alfalfa field near Anna, Illinois; two or three days later, when these plants were examined, they were found to harbor as many bugs as had been present originally. CONTROL OF THE TARNISHED PLANT BuG AND THE STINK Bucs Insecticidal Control. It is very difficult, if not impossible, to control the Tarnished Plant Bug and the stink bugs by sprays or dusts. Arsenate of lead, and other stomach poisons, have no effect on this group of insects, since their food is obtained by sucking the plant juices. They may be killed only by direct contact with the spray or dust. At the time when the fruit needs protection, the bugs are in the adult stage, very active and difficult to hit with a spray, and very resistant to ordinary contact materials. Even if it were possible to kill all the bugs on the trees at a given time, reinfestation would be likely to occur from weeds in the orch- ard or from nearby sources, if such sources of infestation exist. After their period of attack on the small peaches, the bugs return to their normal breeding plants in the orchard or in its vicinity. There is, therefore, no opportunity to attack the young stages of the bugs on the trees in the orchard. The treatment of the immature bugs on the weeds would be impracticable because of the extensive area that would ordinarily have to be covered both in and around the orchard. Another disadvantage of a general insecticide treatment of this nature lies in the fact that it would have to be applied during the summer or autumn in order to protect the following season’s crop, and such efforts would be wasted in the event of subsequent loss of the peach crop by winter-killing or spring frosts. Cage Tests. Because the Tarnished Plant Bugs are so active, our ex- perimental work with contact insecticides has been largely with dusts, which we hoped might envelop them before they had time to escape. Be- fore any orchard tests were made it seemed advisable to make tests to ascer- tain whether the bugs could be killed at all. Accordingly, numbers of Tarnished Plant Bugs and stink bugs were placed in screen wire cages (5 by 5 by 24 inches) and subjected to excessively heavy spraying and dusting, with results as shown in Table II. In interpreting the results of these preliminary tests, it should be borne in mind that the materials were used in excessive amounts and at high strengths, and that the insects were closely confined and had no op- portunity to escape. * Maximum temperatures ranged from 38° F. to 66° F. during this period, reaching 61°, 62°, and 66° on three of the nine days. SoME CAUSES OF CAT-FACING IN PEACHES 273 Control in the Orchard. In using these materials in the orchard, growers are certain to encounter serious difficulties. Contact dusts are essentially open-air fumigants, and their successful use requires a very still atmosphere. In addition, the nicotine dusts require temperatures of at least 70° F. for effectiveness. Weather conditions that permit effec- tive use of contact dusts seldom occur during the brief period when these bugs are present in the peach orchards. In fact, low temperatures, high winds, and frequent rains made it impossible to do effective dusting dur- ing the critical period in the spring of 1927. All of these materials are very expensive, and even if control could be obtained with them, the cost would be high, if not prohibitive. The time during which dusting can be done effectively is short, as will be seen by the graphs in Figure 5. Very little control of the Tarnished Plant Bug would be possible if the operation were delayed for a week. Repellents. Since feeding by the bugs on peaches in spring is not at all necessary to them in their life economy, we have considered the possi- bility of applying some kind of material that would repel them from the TABLE II RESULTS OF PRELIMINARY EXPERIMENTS IN THE CONTROL OF TARNISHED PLANT BUG AND Stink Bues. (INSEcTS CONFINED IN CAGES AND SusJecTeD TO HEAvy Doses.) | Tarnished Materia!s and dosages Plant Bug Stink Bugs \Per cent killea Pe? cent killed DUSTS Galemmpeyanided il-2oVorccm eos see esis s e< on ale = 24 60 Calclumucyanide, 40-nOG ead .steic- Soe oe) cle sie eee nes 90 40 SATAN CV CLINIC Cee etree erat reveretens < citiars cial enard oven'ore. vere } 100 Sultur-napithalene 50-50) ose cence setts < ox cies 25 INT CO GUTOR ate ere: Molcversyniestyateterdusteysithepore ee a oN ES N cue 0 oe INTCOLIN BALD Yo ot eserves a ee STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVII. BULLETIN Article VIII. The ‘“‘Knothead” Carp of the Illinois River BY DAVID H. THOMPSON PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS October, 1928 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVII. BULLETIN Article VIII. The ‘‘Knothead’’ Carp of the Illinois River BY DAVID H. THOMPSON PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS October, 1928 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. SnHetton, Director BOARD OF NATURAL RESOURCES AND CONSERVATION A. M. SHELTON, Chairman WILLIAM TRELEASE, Biology JouHn W. Atvyorp, Engineering Henry C. Cowres. Forestry CuHarLtes M. Tuompson, Representing Epson S. Bastin, Geology the President of the University of Wiru1am A. Noyes, Chemistry Illinois THE NATURAL HISTORY SURVEY DIVISION . STEPHEN A. Forzes, Chief ScHNeEpP & BARNES, PRINTERS SPRINGFIELD, ILL, 1928 87154—1200 VOLUME XVII ARTICLE VIII THE “KNOTHEAD” GARP OF THE ILLINOIS RIVER David H. Thompson FOREWORD The investigation reported here was begun in collaboration with Doc- tor Ludwig Scheuring, of the Bayerische Biologische Versuchsanstalt ftir Fischerei and the University of Munich, during his visit to this country in the winter of 1926-1927. While the “knothead” carp of the Illinois River had been known to the writer for some time, no start had been made on the problem because of the lack of such a fund of information on the biology and pathology of fishes as Doctor Scheuring was equipped to furnish. During the two months when he took an active part in the work in field and laboratory, most of the important facts were brought out, and since his return to Germany he has given advice and suggestions for the continuance of the investigation and has aided in the prepara- tion of the manuscript. INTRODUCTION Any serious hazard fo the carp of the Illinois River is of considerable economic consequence, inasmuch as the carp is by far the most important commercial fish of this stream. Introduced in 1885, out of a stock brought to the United States a few years earlier from Europe,’ the carp first became an important item in the Illinois River fishery soon after 1890. In 1898, the Illinois Fishermen’s Association reported that the carp catch exceeded the value of all other commercial fishes. Statistics gathered by the United States Bureau of Fisheries* show that in 1908 the total yield of commercial fishes of the Illinois River was 23,896,000 pounds, of which carp constituted 64 per cent, or 15,400,000 pounds. More recently, because of the decreased acreage of water due to drainage of bottomlands for agricultural uses, and because of the southward en- croachment of pollution, the annual yield of the entire river has been re- duced about one-half, and even more in the middle section of the stream. 1 Forbes, S. A., and R. E. Richardson. The Fishes of Illinois. Illinois State Nat- ural History Survey Final Report. Vol. III, Second Edition. 1920. 2 Wisheries of the United States. Bureau of the Census. Special Reports. 1908. [285] Intinois NATuRAL History SURVEY BULLETIN “IOATY SIOUI[]] 94} JO divo jeuI10N 42OWw Ton Tue “KNOTHEAD”’ CARP OF THE ILLINOIS RIVER JF Miller Knothead carp of the middle Illinois River. Fie. 2. bo ~~ 288 ILLiINoIs NATURAL History SURVEY BULLETIN The carp has a greater viability under these unfavorable conditions than other fishes and now contributes between 80 and 90 per cent of the total annual catch of commercial fishes. The plant and animal life of the middle Illinois River changed funda- mentally during and immediately following large increases in the load of pollution in the years 1916-1918. One of the changes was a marked alteration in the growth form of the carp. While this alteration varied widely in degree, it was generally obvious in most of the carp and was readily recognized by the fishermen. This change has been found to re- solve itself into two general outstanding differences: retardation of the rate of growth throughout the life of the carp; and marked anatomical abnormalities, especially of the bones. A number of methods have been employed to find out what factors are responsible for these structural and functional changes. Several months of painstaking search gave no evidence of an infection of a kind to have any bearing on this case. How- ever, a variety of information has been accumulated which indicates the presence of developmental and metabolic disturbances similar in many re- spects to those found in rickets among the higher vertebrates, and this has been supplemented with evidence of factors, in both the early and adult food supplies of the carp, apparently capable of inducing diet- deficiency disease. DESCRIPTION OF KNOTHEAD CARP The carp (Cyprinus carpio L.) of the Illinois River are not at all broad or high-backed like the cultivated European races. The malformed carp considered in this paper are, as a rule, still more slender (see Figures 1 and 2) and have a body shape similar to the German wild carp (Bauern- karpfen). The carp of the Mississippi River, on the other hand, tend to have a more fleshy body and a “roach” back and can usually be dis- tinguished readily from Illinois River specimens. This seems not to be an inherent difference but rather a result of more favorable conditions for growth in the Mississippi. Some of the smaller bottomland lakes of the Illinois valley occasionally have their outlets closed during seasons of low water, so that the imprisoned fishes may exhaust the available fish food. Under such conditions of starvation, carp are often found which appear stunted and have the slender form that accompanies the present abnor- mality, but they lack many other readily recognized and more significant characteristics of the abnormal carp described in this paper. “Knothead” is the name that the Illinois River fishermen use most often to designate these abnormal carp, but the terms “lunkhead”’, “pop- gill’, “clam-jaw”, “lump-jaw’’, etc., are also heard. These names all refer to the striking malformation of the head and opercles. The sweeping streamlines of the normal carp are broken up by several irregularities in the conformation of the knotheads. The opercles, instead of being slight- ly convex as in normal carp, are more or less bulged or curled up, with an average curvature about like that of the bowl of a spoon. The skull is eee ea =. ee ee ee ee ee ee ee THE “KNOTHEAD” CARP OF THE ILLINOIS RIVER 289 narrowed and the cheek region is conspicuously sunken between the eye and the opercle. Many of the knotheads have a marked lateral constric- tion or narrowness at the pectoral girdle just back of the opercles, and a more or less well-defined wrinkle over the snout. The head appears gen- erally emaciated, and the sclerotic ring and the sculpturings on the cranial bones can be plainly seen (see Figure 3). On the under side there is usually a depression beneath the chin and a bulge in the region of the heart. All these external peculiarities which are commonly found in the more seriously affected individuals, together with a “drooping” of the fins and general sluggishness of habit, present a very different picture from the trim, sleek, and alert normal carp. Fic. 3. Carp with their opercles removed: a, normal; b, knothead. The knothead malformation is variable, and all degrees of it have been found up to monstrous, emaciated individuals three times as old as normals of the same weight. (See Figure 4.) There seems to be a close correlation in the degrees of malformation of the previously mentioned parts; that is, individuals with slightly bulging opercles have all these parts affected slightly ; those of moderate degree have them all moderately affected, and so on. The bulging of the opercle is the most practical criterion of the knothead malformation, at least for use in the field, but it is so variable that among any dozen carp from the middle Illinois River one or more are usually difficult to classify as normal or abnormal (see Figure 10a). All references to the frequency of knotheads in this paper are based on specimens exhibiting obvious malformation; and specimens that were doubtful or only slightly malformed were commonly included with the normals. When a number of living carp from the middle Illinois River are ob- served in a crib or pond or aquarium, the knotheads are seen to be some- ILLINOIS NaturaL History SurvEY BULLETIN 290 22)/9W4T ‘peoayjouy ouleijxa ‘9 ‘pveyjouy e}e1apom ‘q {[emao0u ‘ev ‘died jo speroy ——— | Pp OMT Og THE “KNOTHEAD”’ CARP OF THE ILLINOIS RIVER 291 what darker and less uniform in color than the normals, the darkest of them usually being the most malformed. The large serrated spines of the dorsal and anal fins are strikingly altered in most knothead carp, being more or less reduced in length, sometimes to vestiges scarcely one-fourth the normal length, and having fewer and shorter serrations, or none at all. The dorsal spine of a normal carp is a little longer than the anal spine, but the reverse is usually true in knothead carp. The spines of knothead carp are often thicker laterally than those from normal carp of the same size, especially in the more distal portions. The right and left halves of these malformed spines are not so closely fused as in the normal spines, and in some instances they can be readily pulled apart. The dorsal spines of the knothead carp are not held erect as in normal carp, but are inclined backward, sometimes lying flat. (See Figures 1, 2, and 5.) Fig. 5. Dorsal and anal spines of carp of the same length: a, normal; b, moderate knothead; c, extreme knothead. “In each pair the dorsal spine is at the left and the anal spine at the right. Many of these abnormal carp have the opercle so highly arched that it fails to reach the posterior margin of the gill chamber; in con- sequence, the opercular membrane does not lap flat on the body wall as in normal fishes, but extends inward or is curled under the edge of the opercle, seriously hampering the mechanics of respirations. In ex- treme cases considerable portions of the gills are always exposed, and the ragged and irregular arrangement of the lamellae in some knotheads may be the result of constant irritation by the edges of opercles that fall short of the posterior margin of the gill chamber. In such cases some of the lamellae have club- like thickenings at their tips (see Figure 3); less often they are partly grown together and show evidence of branching. 292 Fic. 6. heads of the same length: a, normal; Frontal sections through carp b, knothead. MC—mouth cavity; O—opercle; G—gills; OM—opercular ILLINOIS NATURAL History SuRVEY BULLETIN To ascertain whether the bulging of the opercles might be due to an enlargement of the gills as an adaptation to diminished concentration of dissolved oxygen, counts and measurements of the lamellae on each gill were made on one normal and another mal- formed head, with the result that the lamellae were found to be both smaller and less numerous on the malformed head—averaging 15.5 mm. long on the normal head and 11.0 mm. on the malformed, with numbers of the lamellae to each gill as shown in Table I. More- over, the gill chamber in the knot- head was smaller than in the nor- mal, as can be seen in Figure 6. membrane; BW—body wall. TABLE I. NUMBERS OF LAMELLAE ON THE GILL ARCHES OF NORMAL AND KNOTHEAD CARP First Second Third Fourth gill gill gill gill arch arch arch arch Normal 138 i235} 117 118 Knothead 132 122 105 100 A close study of the opercles and the bones of an abnormal head showed no traces of an infection of the bones, either at present or in the past, which could be responsible for this malformation. Some of the bones of the abnormal head were thicker and heavier than those of the normal head, but this may have been due partly to the greater age of the knothead, which was 6. summers old as against 3 summers for the normal carp. Age determination in knothead carp is more difficult than in normal ones, not only because the rings are more crowded as a result of the greater age, but also because there are numerous secondary rings in the scales. This is also true for the growth rings of the cranial bones and the vertebrae. It is possible, however, according to the criteria given by Hoffbauer,*® to distinguish the winter rings from secondary rings, since at the division line of the scale the annuli of the winter ring ® Hoffbauer, C. meine Fischerei Zeitung. Vol. 23, p. 341. Die Altersbestimmung des Karpfen an seiner Schuppe. Allge- 1898. Vol. 25, pp. 135, 150, 297. 1900. —— THe “KNOTHEAD’ CARP OF THE ILLINOIS RIVER 293 diverge, but those of the secondary ring do not. Most knothead carp have scales that are granular and opaque, and it is often necessary to examine large numbers to get a few showing the rings clearly—a con- dition found also among cultiv ated carp that have bee en starved. Dissection and examination of normal and abnormal specimens showed that the skin, gill surfaces, and internal organs were free from infection or parasites; and the color of the gills in the living carp was bright red in both. There is less fat on the mesenteries and pericardium in the abnormal than in the normal ones, but fat is never altogether lacking. The flesh of the knotheads is softer than that of normal carp, although it is not as flabby and watery as in starved carp. Fishermen Ae oy a aber Meta ta tem a8 dl eos eed ws Fic. 7. Microphotograph of gill tissue of knothead carp. of the middle Illinois River say that it is difficult to dress these carp for the market without seriously tearing the flesh and removing portions of it with the scales and skin when they are “fleeced”. This softness of the flesh is well known to fish culturists and has been produced arti- ficially in the experiments of Podhradsky and Kostomaroy.* Examination of the gill tissues of knothead carp gave no evidence of an infection, but sections of the gills showed varying numbers of bod- ies larger than ordinary tissue ce'ls (10 to 20 microns in diameter) and staining differently. (See Figure 7.) These bodies were observed throughout the epithelium of the lamellae and gill arch and occasionally 4 Podhradsky, J., and B. Kostomaroy. Das Wachstum der Fische beim absoluten Hungern. Archiv flir Entwicklungsmechanik und Organismen. Vol. 105, p. 587. 1925 294 ILLINOIS NATURAL History SURVEY BULLETIN in the connective tissue, but most often in the deeper proximal parts of the lamellae. They were found in each of the several normals and knot- heads examined, but were more abundant in the latter. For a time they were thought to be parasites, with perhaps some connection with the knothead disease, but after considerable study it was seen that they had no characteristic resemblance to microscopic parasites of any known kind. They are quite different from mucous cells. They evidently be- long to the tissues of the carp itself, but their place in its histology has not been determined. A knothead carp of moderate degree and a normal one of the same age were selected for comparison from a collection made at Peoria in November, 1927, which was kept alive and under observation several days in large aquaria, in order to make sure that the selected individuals were representative of the two kinds and not obviously injured or af- fected differently by other factors. By taking these precautions, differ- ences due to age, environment, parental stock, etc., were largely elim- inated, so that any observed differences were probably effects of the disease. Data on these two carp are given in Table II. TABLE II MEASUREMENTS OF CARP USED FOR COMPARISON Normal Knothead BZ Hr hy Ros ciee at ee en ae Ro Ee 4 summers 4 summers Tenet ie ss aaron oaieaenenes atin ae Nene 14.2 inches 12 4 inches Depth (at front of dorsal fin) . 5.0 inches 3.9 inches Width (at front of dorsal fin) . 2.9 inches 2.5 inches Weights y, since ur acins ara ee 57 ounces 30 ounces These two carp were anaesthetized, and dorsal and lateral X-ray photographs were made of them by Dr. C. S. Bucher at the Bucher Clinic, Champaign, both being rayed at the same time and on the same sensitized surface in order to maintain conditions as uniform as possible. These X-ray photographs, reproduced in Figures 8 and 9, show many of the malformations already described—the bulged opercles, sunken cheeks, narrow pectoral girdle, etc. Examination of the original negatives by strong light also shows a difference in the thickness of flesh on top of the head. In the normal specimen the median ethmoid, frontals, parietals, and pterotics, are overlaid by flesh 1 to 2 millimeters in thickness, while in the knothead practically none is visible over the frontals, parietals, and pterotics and a layer only % to 1 millimeter thick over the median ethmoid. These X-ray pictures, besides confirming observations already made and revealing further malformations, give a clue to the more intimate nature of these malformations; for, other factors being substantially equal, the depth of the “shadow” cast by a bone depends mainly on the thickness of that bone and its degree of mineralization. Fig. 8. THE “KNOTHEAD” CARP OF THE ILLINOIS RIVER Dorsal X-ray photographs of 4-year-old carp: a, normal; b, knothead. 296 ILLINOIS NATURAL History SURVEY BULLETIN The heads of the two 4-year-old carp used in the above compari- son were heated almost to boiling, and the flesh was cleaned off the skulls and the bones of the pectoral girdle. The right opercle, the right cleithrum, and the right pharyngeal bearing the teeth were selected from each for chemical analysis. These bones were weighed and their per- centages of ash and calcium determined by Mr. O. W. Rees, chemist of the Illinois State Water Survey, and the weights and percentages are given in Table III as an indication of the degree of mineralization. TABLE IIT Weight of bone Ash Caleium in grams Per cent of Per cent of Dried at 105°C. bone weight bone weight Right opercle Normal i 1.2705 56.0 21.2 Knothead 1.0243 54.7 21.3 Right cleithrum Normal 0.9700 50.0 19.6 Knothead 0.6262 53.3 21.3 Right pharyngeal bearing teeth Normal 0.7562 51.3 15.8 Knothead 0.3489 54.1 LM, The analyses show that the percentage of ash is about the same in both the normal and the knothead and that the percentage of calcium is slight- ly greater in the bones of the knothead. The calcium determination is of greater significance for comparison of X-ray “shadows”, since calcium is the only element of importance in bone which produces the shadow. The percentages of calcium, however, are so similar that any consider- able differences in the X-ray shadows of corresponding bones of the two heads are probably due to differences in the thickness of bone penetrated. The shadows cast by the various bones of each head in the present comparison differ greatly in density. The roentgenograms show that the frontals, parietals, pterotics, opercles, and a few other bones of der- mal origin on the top and sides of the knothead skull are more opaque to X-rays than the corresponding bones in the normal. The denseness of these malformed bones is not evenly distributed, but is most pronounced near the ossification centers, while other parts of the same bones often cast lighter shadows than the corresponding parts of normal bones. The deeper-lying bones of the knothead skull, both of dermal and chondral origin, throw lighter shadows than corresponding normal bones because they are generally thinner. Many of the longer bones of the skull are not only thinner in the knothead but are often much narrower than the ratio of the lengths of the two would indicate. The greatest differ- ence in the shadows cast by the bones of the two skulls is to be found in those about the base of the skull, which are perhaps the deepest- lying bones of the head. THE “KNOTHEAD”’ CARP OF THE ILLINOIS RIVER 297 Fic. 9. Lateral X-ray photographs of 4-year-old carp: a, normal; b, knothead. 298 ILLinoIis NAtTuRAL History SURVEY BULLETIN The relation of the weight of the bones of the head to their depth beneath the surface is well shown in Table III. The opercles are covy- ered by only a thin skin and are taken as representative of the peripheral bones. The ratio of the weight of the normal to. the knothead opercle is 1:0.81. The cleithra form part of the pectoral girdle and are of in- termediate depth. The ratio of their weights is 1: 0.64. The pharyngeals that bear the teeth are fairly large and more easily removed entire than the other deeper-lying bones. Their ratio is 1: 0.46. This pronounced thinness of the bones of the occipital region of the knothead skull is quite obvious in the cleaned skulls. While the Kknot- head skull is actually smaller than the normal, its foramina for the pas- sage of nerves and blood vessels are almost always actually larger. The two heads had been heated in the same vessel of water and cleaned and treated throughout in the same manner, and the skulls had been air dried in the same box; but the thinner bones forming the brain case of the knothead skull opened at the sutures, leaving gaps occasionally more than a millimeter in width. These gaps are not due to a general disarticula- tion of the skull, because it is still held firmly together by the heavy bones on top of the head and the parasphenoid. No such gaps appeared in the normal skull as it dried. Those of the knothead skull are appar- ently produced by differential shrinkage of the heavy, dense bones form- ing the roof of the cranium and the thin, lightly mineralized bones lying deeper in the head. X-ray photographs of knotheads of different degrees of malforma- tion, from slight to extreme, made for comparison with the one of mod- erate degree we have been considering, are shown in Figure 10. The extreme knothead (Figure 10d) shows heavier and denser bone at the ossification centers of the peripheral bones of the skull than those in Fig- ure 8b, and these centers of heavy ossification are lacking in the head with only a slight degree of malformation (Figure 10a). Photographs of the skulls from these two heads are reproduced in Figure 11. The difference in conformation is greater than would have been suspected from the appearance of the living fishes or from their X-ray photographs. The areas of heavy mineralization found in the peripheral bones of the knothead are visible in its skull as unusually heavy sculpturing and ridging at the ossification centers. The anterior margins of the malformed opercles have a slightly inflated appearance, and, when freshly cleaned, they had the red color of cancellated bone tissue. There are further alterations in shape and details of structure in every bone of the knothead skull, but a detailed description of them is hardly justified in this account. In proportion to the length of the spinal column, the head in these malformed carp is 2 to 5 per cent shorter than normal. This is under- standable in view of the fact that there is no malformation visible in the vertebrae of the knotheads, either by direct examination of the bones or from their X-ray shadows. a A, Te ee ee a ee a a ae i a I sw ee ee ST ee eee ne ee ee Dal rat ets mn. en aioe At iin ee ee a THE “KNOTHEAD’ CARP OF THE ILLINOIS RIVER Fic.10. Dorsal X-ray photographs of knotheads showing different degrees of malformation: a, slight; b, moderate; c, moderate; d, extreme. 300 ILLINOIS NATURAL History SURVEY BULLETIN Differences in the intimate structure of the skull bones of normal and diseased carp were studied by means of X-ray photographs made by Dr. G. L. Clark of the University of Illinois by the monochromatic pin-hole method,’ showing the degree of diffraction of a beam of X-rays passed through the bone. The crystals of both were found to have a random orientation and to be within the range of size of colloidal particles, those of the knothead being slightly larger than those of the normal—a fact which substantiates previous observations of the greater brittleness of knotheads’ bones. DISTRIBUTION OF KNOTHEAD CARP Carp fingerlings with bulging opercles were first noticed in the fall of 1918 in the Illinois River at Peoria. Fishermen report that knothead 5 Clark, G. L. Applied X-rays. McGraw-Hill Book Co. 1927. Fic. 11. Skulls of 4-year-old carp: a, normal; b, knothead. THE “KNOTHEAD’ CARP OF THE ILLINOIS RIVER 301 carp began to appear in the catch of market-size fishes in 1920, and that the percentage of knotheads increased rapidly, reaching about 50 per cent in 1922 at several points on the river. In order to find out more definitely the distribution of the malady and the percentage of market-size carp affected, many points on the river were visited during 1926 and 1927, and catches of carp were examined and information was obtained from fishermen. A summary of the data is given in Table IV, and the location of sampling stations is shown in Figure 12. These data were all obtained during the winter of 1926-1927 except the Peoria and Meredosia numbers, which are for the summer and fall of 1927. The rather high percentage of knotheads at Peoria is largely due to the recognition of slight degrees of malformation in individuals such as had formerly been included with the normals. The observed percent- ages are based on hoop-net catches and give a more accurate measure of the proportion of knothead carp than hauls made with seines which have larger meshes and allow many of the stunted and slender knot- heads to go through. In the course of several years work on the fishes of Rock River, less than a dozen knotheads have been noticed among the many thou- sands of carp taken. Careful examination of catches of carp from various parts of the Mississippi Valley in the Chicago markets has oc- casionally revealed a few individuals with distinctly knothead character- istics. Indirect reports have been received of large numbers of knot- head carp being taken in Lake Pepin on the Upper Mississippi, but no direct information has been available as yet on this point. RELATION TO POLLUTION The beginning of this malformation among the carp was coincident with a period of very rapid increase in pollution, due partly to an increase in the population of Chicago and other cities which pour their wastes into the river, but still more to the war-time boom in many industries, particularly those engaged in the packing and manufacture of food prod- ucts. The subsequent fundamental alteration of the character of the bottom fauna of the Illinois River has been described by Richardson in the various publications of the Illinois Natural History Survey. As indicated in Table IV, knothead carp range from Utica (Starved Rock) down to the Copperas Creek Dam with only occasional individuals below that point. There are no fishes of any kind above Utica, since, because of pollution, the amount of dissolved oxygen in that part of the river is so low throughout most of the year that fishes can not live. As long ago as 1912 Utica was the upper limit of most of the species of fishes in the Illinois." The few species that were occasionally found above that point disappeared completely. according to the reports of fishermen, in the years between 1912 and 1917. 6 Forbes, S. A., and R. E. Richardson. Studies on the Biology of the Upper Illi- nois River. Ill. Nat. Hist. Surv. Bull. Vol. IX, Art. XX. 1913. it) 302 ILLinois NArTurRAL History SURVEY BULLETIN In the years since 1917, pollutional conditions have prevailed over a hundred-mile stretch of the middle Illinois River, and the fishery yield of this section has shown marked reduction as compared with the yield before 1917. The fishes themselves are largely restricted to the cleaner boitomland lakes and backwaters of this section. The carp, being of more tolerant habit than other fishes, have continued to range over a large part of this pollutional area except during periods of severe oxygen depletion TABLE IV DISTRIBUTION AND PERCEN'TAGE OF KNOTHEAD CARP IN THE ILLINOIS RIVER DuRInG 1926 and 1927 | Stations | Number Observed per- ’ ; zone | of carp centage of Information and estimates downstream | examined | knotheads of loch I> ashe | Utica MOTO. Piece can Fae About 50 per cent of the carp are knotheads. This is the upper limit of fish life in the Illinois River. Bh oie About 50 per cent of the carp are knotheads. Depue 23 91 Not as many knotheads as this sample indicates. 60 to 75 per cent is more nearly correct. Henry 316 75 60 per cent is more nearly correct as a year-round average. Chillicothe ua ey 64 About the correct proportion. Spring Bay 302 46 Hardly as many knotheads as usual from this place. Averyville 149 57 About the correct percentage. Peoria 256 78 The carp in Lower Peoria Lake average 50 to 60 per cent knot- heads. Pekin about 500 about 30 About average percentage of knot- heads. Knotheads are found downstream as far as the Cop- peras Creek Dam. The knot- heads here are not slender and many even tend to be pot-bel- lied. Havana 539 none An occasional knothead carp is taken which is believed to have straggled down the river from where they are plentiful. The percentage is extremely low, as only a few individuals are taken among many tons of carp. Beardstown 3 none No knothead carp have been seen here. Meredosia 42 2 Fishermen have not noticed knot- head carp here. The one taken was of moderate degree and pot- bellied. LaSalle-Peru none THE “KNOTHEAD’’ CARP OF THE ILLINOIS RIVER 303 in summer and under heavy ice in winter. The distribution of knothead carp coincides, both in main features and in detail, with the areas of greatest change in sanitary condition. Below the Copperas Creek Dam the carp are all normal except for occasional knotheads that have straggled down the river. Natural purification of the sewage load of the upper and middle river is approach- ing completion in midsummer by the time this lower section is reached ; ekate. =o S| S OF Fic. 12. Sketch map of the Illinois River. and there has been no general or serious alteration in the character of the food supply of the carp. The observed percentages of knotheads at various points on the Illinois River indicate that the proportion of affected carp decreases downstream, as is to be expected if the malformation is correlated with pollution. 304 ILLINOIS NATURAL History SURVEY BULLETIN The knothead malformation appears among those races of carp with reduced scalation (mirror and leather carp) to the same extent as among the scaled variety. The proportion of these mutant races of carp in the original stock of the Illinois River was quite large, but their numbers soon decreased to the present proportion of one or two per cent of mirror carp and still fewer leather carp. The carp populations of other waters of the Mississippi Valley show these varieties in about the same proportions. The occasional occurrence of a few knotheads in the Rock River and other waters seems to have no relation to pollution. No malformations similar to those of the knothead carp have heen found in other species of fishes of the middle Illinois River. During the course of this and other investigations considerable numbers of about twenty species of larger fishes from this section of the river were handled without any appearance of alteration in their growth form, but an ex- amination of other cyprinoid fishes (minnows) of this area might dis- cover an abnormality like that of the knothead carp.‘ CHANGES IN THE FOOD SUPPLY OF THE CARP The following statement by Mr. R. E. Richardson concerning re- cent changes in the natural food supply of the carp in the middle river is based on various field observations and unpublished plankton data in the possession of the Natural History Survey, accumulated between 1910 and 1925. The most significant changes in the plant and animal food supply of the carp in the middle Illinois River in recent years had to do either directly or indirectly with the plankton and the coarse aquatic vegeta- tion. That the latter usually serves to some extent as green forage for carp above the late fingerling stage can hardly be doubted, though the exact extent to which either the roots or the stems or other parts of coarse aquatic plants enter into the normal food supply of these fishes has not been quantitatively determined. The almost complete extermina- tion of the Potamogetons and other large plants in Peoria Lake and also in the river and in its connecting lakes and sloughs far below that point, between 1915 and 1920, left large numbers of carp practically without any green forage at all for several seasons. Since 1922 or there- about, restoration of the Potamogetons particularly has proceeded rather 7Some young goldfish, spawned in the summer of 1927 in the University of Tlli- nois lily pond, were brought indoors in October and kept in a large aquarium, which was supplied with running tap-water and aerated with compressed air. They were fed commercial goldfish food occasionally, and there was no other food available except mud on the bottom. There were no algae or other green plants present. The fishes were an inch to an inch and a half long when they were brought indoors, and they did not grow perceptibly afterwards. In December some of them showed signs of emaciation and an oceasional one died. About half of the 50 fishes in the aquarium on December 15 had distinctly arched opercles, most frequent on the emaciated fishes but present also on some of the fleshier ones. Those with arched opercles also showed the sculpturing of the skull bones, the drooping fins, the narrow pectoral girdle, and the general sluggishness characteristic of knothead carp. More recently a few golden shiners with strongly bulged opercles have been found in the Salt Fork River in Champaign County. THE “KNOTHEAD” CARP OF THE ILLINOIS RIVER 30 o rapidly in many sections of Peoria Lake as measured by the areas af- fected, though the growths are yet generally very sparse as compared with those of the pre-1920 years, and the areas covered are still decidedly smaller. The distinct change in the general composition of the normal summer plankton in the section of river extending from Spring Valley to a point in Peoria Lake only a few miles above Peoria Narrows, between 1913- 1915 and 1920, was probably no less important in its final effects than the reduction in the coarse aquatic vegetation as an item in the general reduction of the green forage supply that took place during the period as a result of pollution; and this has continued substantially without visible relief up to the date of our latest observations. This change in- volved the substitution on a large scale of non-chlorophyll-bearing Pro- tozoa for chlorophyll-bearing kinds, and the replacement of vast numbers of DiaToMACEAE and CHLoROPHYCEAE by filamentous or non-filamentous blue-green algae. The change was so marked in the summer of 1920 be- tween Chillicothe and the foot of Upper Peoria Lake that the water, which in former years had shown a normal pale-green tint when rela- tively free of silt during the hot season, took on a distinctly blackish tinge, apparent to the unaided eye in bright sunlight. The recovery of the diatoms and CHLOROPHYCEAE as well as of other green microscopic forms, was quite rapid both that summer and in the summer of 1922 below the upper third or half of Middle Peoria Lake—a fact enabling us to make fairly satisfactory, though rough, colorimetric determina- tion on given days of the location of the boundary line between pre- ponderance of blue-green and green plankton by observing the change in color of the plankton samples in the bottle in the field a few minutes after pouring on the alcohol-formalin mixture used for preservation. A similar boundary line between the greens and the blue-greens of the plankton could be made out in the same way in the summers of 1911 and 1912 at points usually lying only a short distance below Spring Valley. These changes in the plankton could obviously affect directly the fry of carp and other fishes depending upon it for their first food. A far more important effect upon the carp between the fingerling and adult stage could apparently be exerted through the medium of the bot- tom, shore, and limnetic organisms of microscopic size, which had fed upon the plankton and had later entered into the carp’s rations in the same or adjacent areas. During the same period (1913-1915 to 1920- 1922) the changes in the principal constituent organisms of the small bottom fauna,‘ though also great in degree, appear to have been in them- selves of no particular importance to the health of the carp and other bottom-ranging fishes. The increased restriction of the diet of the small bottom animals above Peoria to microscopic organisms lacking in chloro- phyll or food elements, such as vitamins, directly or indirectly derived from it can easily be believed, however, to have been capable of caus- 8 Richardson, R. E. The bottom fauna of the middle Hlinois River, 1913-1925; its distribution, abundance, valuation, and index value in the study of stream pollu- tion. Ill. State Nat. Hist. Surv. Bull. Vol. XVII, Art. XII. (In press.) 306 ILLINOIS NATURAL History SURVEY BULLETIN ing disturbances both in the growth and metabolism of fishes confined to these small bottom animals for food, if the requirements in that re- spect of man and many lower animals above the grade of fishes are to be accepted as in any sense a usable criterion. RATE OF GROWTH OF KNOTHEADS During the winter of 1926-1927, representative samples of carp, obtained from fishermen at various points on the Illinois River, were weighed to the nearest ounce and measured for length and for depth at the front of the dorsal fin, and about twenty scales were taken from the left side of each fish between the dorsal fin and the lateral line. The carp were classified into normals and knotheads, but many with doubt- ful or slight degrees of malformation were included with the normals. The scales were cleaned and age determinations were made by counting the winter rings of at least ten scales from each fish. Scales which have been regenerated, and consequently have smaller numbers of win- ter rings, can usually be recognized by their irregular shape, and avoided. The data on the age and weight of normal and knothead carp at various points on the Illinois River are given in Table V. Differences in age of normals and knotheads of the same size are shown in Table VI, the data of which have been arranged in twelve 5-ounce weight classes and the ages of the two kinds compared in each class. The knotheads average older than the normals in each of the twelve classes. Arithmetical averages (not weighted) of the ages of the two kinds in the first six and the last six classes show that the differ- ence in age between normals and knotheads of the same size is much greater in the heavier classes. Growth curves plotted from the data in Table VI are shown in Figure 13. These curves indicate that the stunting effect of the dis- ease is cumulative and stops growth altogether in the knotheads at the time when normals are growing most rapidly. Since it has been obvious throughout the investiga- tion that growth is retarded in pro- portion to the degree of malforma- tion, it seems probable that carp with slight degrees of malformation have a growth rate intermediate be- tween normals and knotheads, and the inclusion of knotheads of slight ACE IN. YEARS degree with the normals has prob- Fie. 13. Growth curves of normal ably resulted in an appreciable low- and knothead carp of the Illinois €ting of both the curves between River. the third and sixth years. 20) THE “KNOTHEAD” CARP OF THE ILLINOIS RIVER 307 Calculated from the data in Table VI, the average individual growth rate of normal carp is about 11 ounces a year® and that of knothead carp is only about 6 ounces a year. There is no considerable variation in the growth rate of the former from one end of the river to the other, but the growth rate of the latter tends to increase downstream. Thus the lowest rate for knotheads, 3.8 ounces a year is at Depue, while the highest rate, 9.1 ounces a year is at Pekin. The greater growth rate down the river is strikingly reflected in the body contours of the knotheads. A large number of them were seen at Pekin and practically all, instead of being more slender than the normal, were pot-bellied—a condition strikingly illustrated in a sin- gle knothead taken at Meredosia in July, 1927, a drawing of which is shown in Figure 14. An examination of the gonads of this fish showed that it was a spent female. Its scales showed that it was four years old, and the relatively greater width of the last two growth rings indi- cated that in those years growth had gone on at a relatively rapid rate. JEMiller Fic. 14. Pot-bellied knothead carp from the lower Illinois River. The 30 per cent or so of pot-bellied knotheads seen in catches from the stretch between Pekin and the Copperas Creek Dam may indicate either that the conditions associated with pollution and inducing malformation were of short duration or else that these fishes migrated downstream, perhaps from the Peoria Lake region, after their growth form had been altered by exposure to the knothead-inducing conditions during their early life. The development of the pot-belly seems to indicate that, under non-pollutional and hence more favorable conditions, the viscera tend to grow at a normal rate while the growth of the skeleton and mus- cles of the carp is permanently retarded. ® Doctor Scheuring says that the growth of normal carp in the Illinois River is about as rapid as under fairly good cultivation in Germany. ILLinois NATURAL History SURVEY BULLETIN 308 | 9b ze | ee | 82 | 8z Te 8z ee 82 82 Le 69 SL ord G2 9% G62 aye] [Tues | AUNGH | | ze | 92 8% | | 82 12 | 02 | GL 9L eZ +L oe bl 8 be LL SL ei) sl GL LL OL ZL g SPIT aye] endeq — | | | | anda | GI6l 916E LI6E SI6T GIGT OZ6T 126T G26T 8c6L F261 S26 is poumeds 1eoX UBSIYOIIN OYe'T £ype00 we! 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A! CFSE | LEEE | SE-8S | LZ-ES | ZE-8T T 1 l l UOT}eYS LL-€L GL789 | 19-9 | G9-8S | LS-Eg GS-8h | LEEF | X | U)}/A/Ual;yX| ul; AXl|ul yX\|uU ‘Spvoyjouy pue sTeuliou YOq epnjour JOU Op Aay} asneoeq pa}}IWIO a1B SadUNO J} AAOGE PUL Sa0UNO gT MOT[aq SaSseID S€SSV1) LJHSIAM FAONOOG NI GADNVYYY YAAIY SIONTIT] AHL AO duvO GVAHLONY GNV TIVNYON dO SuvaxX NI ay IA aay, ILLINOIS NATURAL History SURVEY BULLETIN 09L GR, ae eh REE Geant el eh. aN A GVHHLONY 19°F (ii je pa Sa wel ome ze +) WON Sivek Ul o8e BSRIOAY 20 LU-8h 0 iis Geeta 2 gina pepe ie Bore SOSSEIO IYSIOM =, 32 Se — = OL 09 06 g°¢ 0s ccGea gg CoG iar eon rts GVHHLONM 0° Ge OF oF aF eF ge ge feccsssttttse TVWUON | sired Ul o8B aSeicAy ¢ | eo aleee age) teal eee -* UMojspreeg g S 9 | G i | G i G y a4 y | i 7 g U7 9 y v i 4 G G G i t t § al $ | ? $ } g | (du PRE. On cot oda oo O8 BUBARTT | 9 Pale eeesieesyole Soy ee upped 6 9 ¢ Fy | ee |e tea| BeeoRs une onuresnes - B0eg | | ? HC |) |) || te |Ja}/yx|u|y|ul| ¥ | mole1g | L9-&9 69-8S LG-ES | Le-sp | Zr-8s | Le-es | cE-8¢ 312 papnjauog—IA FI1adVL, THE “KNOTHEAD” CARP OF THE ILLINOIS RIVER 31 oo BEHAVIOR OF KNOTHEAD CARP The reactions of knothead carp to their environment differ from those of normal carp in many details. Our present information, although rather fragmentary, shows that some of the differences in behavior are of considerable importance, and that they are attributable to various manifestations of three defects found in the knotheads—an inefficient respiratory apparatus, a general flaccidity of the body that implies a lack of muscular tone, and a comparatively low sensitivity to stimuli. Many fishermen of the middle Illinois River have given us infor- mation concerning knothead carp and their habits, one of the most important items of which is a difference in the habitat of normal and knothead carp. Carp are distributed throughout many kinds of situa- tions in the Illinois River proper, in the connecting bottomland waters, and in Peoria Lake, which is a widening of the river. Those taken from situations where there is a considerable flow, and where it is prob- ably necessary for them to swim more or less constantly to hold their position, are almost invariably normals. The catch from the deeper quiet waters includes both normal and slightly deformed carp. Most of those taken from the shallower backwaters of the section between LaSalle and Peoria, extensive areas of water choked with brush and vegetation, have moderate degrees of malformation. The writer has examined single catches with as many as 200 carp from these shallow backwaters without finding a single entirely normal individual, although during periods of high water, normal carp are taken there in fair num- bers along with knotheads. In summer extremely malformed and emaciated knotheads can of- ten be picked up by hand where they are lying quiescent in shore vege- tation. These are known to fishermen as “grass” carp. Their behavior suggests that extreme malformation has so embarrassed respiration that they can live only in relatively high concentrations of dissolved oxygen, and that they are so occupied with getting sufficient oxygen that they do not feed or react to ordinary stimuli. Such individuals are often found dead in nets and along the shores. A large part of the commercial catch of carp is taken by means of hoop-nets set along the shores and in other shallow waters from 2 to 8 feet deep. The openings of these nets are directed downstream and are flanked by wings to guide the fishes into the openings. Such nets capture, of course, only those fishes that swim into them, and their usefulness depends on the fact that the fishes react to small changes in environmental factors, such as stage of water, temperature, turbidity, rate of flow, waves, light, ice movement, dissolved oxygen, and food supply. Since minor changes in these factors occur from day to day, some fishes are always moving from place to place, and a more or less constant number of them are taken daily in these hoop-nets. The catch of knotheads, however, is more irregular than that of normal 314 ILLtinois NAaTurAL History SURVEY BULLETIN carp and other fishes. This indicates that the knotheads do not so readily react to these minor changes in condition, but are quiescent for long periods of time. When major variations of environmental factors cause them to move, they are taken in large numbers, because they are less alert and more blundering than normal carp. For example, an up- stream wind apparently drives these knotheads before it along the shores, where they are taken in large numbers by hoop-nets. The first fingerling knothead carp seen by the writer had been washed ashore in late August, 1923, while the laboratory boat was tied up at Peoria Narrows. An upstream wind which blew continuously for several days, producing waves a foot or more in height, caused thousands of small carp and a sprinkling of other small fishes to be thrown up on the beach, along with uprooted vegetation and miscel- laneous debris. These little carp were apparently uninjured, and a quantity of them were gathered up and kept alive for several weeks in the large aquarium on the laboratory boat. They were from 1 to 3 inches long and were obviously of the brood spawned during May and June of that year. At that time the local fishermen pointed out that many of these young carp had the bulged opercles characteristic of the knothead fish that had been numerous in their catches. They further remarked that it was very unusual for carp to be driven ashore, inasmuch as the carp, of all fishes in the river, are the most alert and best able to take care of themselves. Occasionally the Illinois River is frozen over for a few weeks in winter and a condition of stagnation develops which is accompanied by a decrease in the amount of dissolved oxygen in the water.” When the amount of dissolved oxygen in the heavily polluted channel waters drops to 3 parts per million or less, the fishes begin to retreat into the back- water lakes, spring holes, mouths of tributaries, and other places where there is more oxygen. At such times large hauls of fishes are taken by fishermen in certain spring holes, the best known of which is at Spring Bay in Upper Peoria Lake, where 200,000 pounds of carp were taken in December and January, 1917-1918. Large numbers were taken there also in the winter of 1924-1925, and a fair number in the winter of 1926-1927. The early hauls from this spring hole are almost all knot- head carp, but later hauls, made after stagnation in the river is more advanced, are mostly normal carp. This is further evidence that the knotheads are more quickly affected by low oxygen concentrations than are normal carp. Illinois River fishes often have a very disagreeable “gassy” taste or odor, which seriously lessens their palatability, and these gassy fishes are definitely associated with periods of prolonged ice on the river, mortality in nets and traps, and other indications of a scanty oxygen supply. Fishermen find that this gassy taste occurs more often and is more pronounced in knothead than in normal carp, and for this reason Thompson, David H. Some observations on the oxygen requirements of fishes in the Illinois River. Ill. Nat. Hist. Surv. Bull. Vol. XV, Art. VII. THE “KNOTHEAD’ CARP OF THE ILLINOIS RIVER 315 the knotheads are culled out when carp are shipped to New York from the Illinois River, because it is very costly to ship such long distances by express and any defect in the quality of the fish is likely to cause them to be docked in price to a point where the money received will not pay the transportation charges. To remove this gassy taste, fishermen place their fishes for a week or two in cribs or ponds fed by spring or other well-aerated water. A spring-fed pond of about half an acre has been constructed by a fishing firm on the east shore of Lower Peoria Lake as storage space for live carp. In warm weather the carp are hardened in this cold spring water before they are shipped alive in tank cars to New York, and in winter they are left in this clean, well-aerated water for a few weeks to improve the flavor. The first live carp were put in this pond for storage during the latter part of the summer of 1927, and by the middle of September about 120,000 pounds had been accumulated. During a fortnight of very warm weather in September some of these fishes died of suffocation, and it was noticed that the first to die were almost all knotheads, and that those dying a few days later were both normals and knotheads. A few dissolved-oxygen determinations made at this time indicated that the knotheads began to die in numbers as soon as the dissolved oxygen fell to about 2.8 parts per million, and that the normals began to die when it had fallen to about 2.45 parts per million. The weather turned cool, the aeration of the spring water was im- proved, and the carp stopped dying. Some determinations made a little later showed about 5 parts per million of dissolved oxygen in various parts of the pond. At this time many of the knotheads were lying in the shallow water at the margin, while the normals were moving about in the deeper parts of the pond or making repeated attempts to ascend the stream of spring water as it poured in. These normals kept their fins fully extended and were seldom quiet for more than 2 to 5 seconds, but the knotheads would lie on the bottom for many minutes at a time, seldom moving unless they were nudged by other fishes. Their fins were rarely fully extended, and the dorsal was usually inclined backward or lying flat. Three normals and six knotheads, each weighing between 1% and 3% pounds, were hauled from this pond to the laboratory at Urbana in 10-gallon cans and kept in a large aquarium in well-oxygenated water at about 62°F. The average numbers of respiratory movements per min- ute of five of the knotheads were 61, 63, 67, 69, and 87. Although accur- ate counts could not be made on any of the normals because they were constantly moving about, their respiratory movements were obviously slower than those of any knotheads and were estimated to be about 50 per minute. The relative viability of the two kinds is indicated by the fact that 4 of the 6 knotheads died during the first three days while none of the normals died. The death of the former could not have been due to over-crowding or lack of oxygen, because the aquarium was 316 ILLINoIs NATuRAL History SURVEY BULLETIN large and was supplied with a good flow of well-aerated water which was further oxygenated by bubbling compressed air through the tank. This greater loss of the knotheads is experienced by fishermen who ship carp to New York in tank cars that are constantly aerated by air com- pressors. The supernumerary rings on the scales seem to indicate that the knotheads stop feeding for considerable periods of time during the grow- ing season, perhaps because of embarrassment in respiration during periods of dissolved-oxygen deficiency in summer. ETIOLOGY OF KNOTHEAD DISEASE The possible causes of malformation in fishes are usually consid- ered as falling into three classes: (1) hereditary defects, (2) infections, and (3) environmental changes that disturb the normal metabolic and developmental processes. There is no reason to suppose that the knot- head malformation of carp is hereditary; neither has any evidence been obtained, during several months of work on the histology and morphology of knotheads, of an infection of any kind that could produce it. The first two possible causes of malformation being thus eliminated, it seems probable that we have to deal with some external influence which has interfered with the developmental processes or the metabolism of these carp and has altered their growth form. No significant similarity has been discovered between the knothead malformation and any of the many abnormalities that have been pro- duced in fishes by various workers by changing the physical and chemi- cal conditions of the medium during the egg and early embryonic stages. Double-headed monsters, multiplication of parts, coalescence of parts, supernumerary organs, etc., such as have been described by O. Hertwig, G. and P. Hertwig, Mielewski, Stockard, Tornier, Werber, and others, obviously have nothing in common with the malformation we are con- sidering. The explanation of knotheads, therefore, is to be sought in terms of metabolic disturbance. The marked difference in the growth rates of normal and knothead carp is direct evidence of some metabolic change, the production of large numbers of knotheads in a certain part of the river indicates some © general environmental cause, and the fact that growth is retarded through- out the life of these fishes indicates, further, that the causative con- ditions are persistent in this area. The few pot-bellied knotheads, which we have found farther downstream, are individuals that partly recov- ered after they had escaped from the waters in which the causative conditions obtained. It has been shown that the distribution of this abnormality coin- cides with a certain pollutional area of the river, and this limits the causative agent to conditions which accompany pollution. The fact that carp alone show abnormality delimits the cause to some condition which affects carp and not other fishes of the area—on the supposition that THE “KNOTHEAD” CARP OF THE ILLINOIS RIVER 317 the innate liability of all fishes of the area to abnormality is the same. In the middle Illinois River under pollutional conditions, carp constitute a much higher percentage of the total catch of fishes than in the cleaner waters of the lower river. This is mostly because the carp are more tolerant of pollution and feed over much larger areas than the other less tolerant fishes, which are mostly restricted to the cleaner backwaters of the region. The character of the food supply available to the carp in this region has been strikingly altered by the pollutional conditions which have prevailed during the past decade. Since the other fishes have been restricted to the cleaner backwaters, probably no marked change in their diet has been produced. Since no other condition affect- ing only the carp is known which could conceivably induce metabolic disturbances, food is taken to be the causative agent of the abnormality. In recent years, many metabolic disturbances traceable to food have been found to be due to the lack of certain food elements, or vitamins. To date, very little is known about diet-deficiency diseases except in man and a few other warm-blooded animals, but in the latter the changes resulting from the lack of the different vitamins have been fairly well worked out. The knothead malformation shows definite changes in calcium meta- bolism, since the bones are altered in shape and thickness; the bones of the skull are malformed while the vertebrae are unaffected; there is also a marked lack of muscular tone, as indicated by the flaccid body and general sluggishness of the affected fishes. In warm-blooded animals such symptoms have been found to be associated with the lack of vitamin D. Growth curves for experimental rachitic and normal rats’? are prac- tically identical with the growth curves for knothead and normal carp. In the higher vertebrates, where the etiology of rickets has been worked out most completely, the most characteristic symptoms are found in the long bones of the appendages and in the ribs. Critical comparison with rickets as known in these higher animals is made difficult, however, by reason of the fact that the carp has no long appendicular bones and its ribs are haemal bones, not homologous with the pleural ribs of the Terrapopa. In the long bones of the latter a very characteristic indica- tion of rickets is to be found in the tissues about the line of calcification in the epiphyses,’* but there are no epiphyses in the skeleton of the carp. Sunlight or ultra-violet rays seem to be essential to the production of the antirachitic factor, vitamin D. A number of workers*® have pointed out that our richest sources of vitamin D are animals, such as the cod, which feed directly or indirectly on chlorophyll-bearing, and hence sunlight-loving, plankton and other green organisms. Rickets is 1Cahan, M. H. Studies of cholesterol in prevention of rickets. Thesis. Univer- sity of Illinois Graduate School. 1927. = 2 McCollum, E. V., and N. Simond. The new knowledge of nutrition. Macmillan Co. Third Edition. 1925. 18 Coward, K. H., and J. C. Drummond. On the significance of vitamin A in the nutrition of fish. Biochemical Journal, Vol. 16. 1922. 318 ILLtinois NATURAL History SURVEY BULLETIN commonly cured either by the direct effect of sunlight or ultra-violet light, or else by a diet containing vitamin D. The fact that the peripheral bones of the knothead skull are thickened suggests the direct effect of sunlight on the local deposition of bone. The origin of the knothead ab- normality among the carp of the middle Illinois River seems, then, to be due to the replacement of chlorophyll-bearing plankton by non-chloro- phyll-bearing kinds and to the loss of the coarser aquatic vegetation from the dietary of the carp and of the organisms upon which they feed; but extensive feeding experiments under carefully controlled conditions would be required to determine positively whether or not the knothead malfor- mation is due to a lack of vitamin D. Experimental work on fishes has not produced anything similar to knotheads. Among the entire group of cold-blooded vertebrates, the only known abnormality comparable to the knothead malformation was seen by Klatt* in Triton and Rana which he had fed exclusively with mussel flesh. The heads of these amphibians were short, broad, and oedematic, and their bones were not normally calcified. Coward and Drummond (op. cit.) found that brown trout fry fed on a diet deficient in vitamins A and D did not grow much or show the vigor of those which received a diet rich in A and D. In Germany, a carp disease characterized by a softness of the bones (Knochenweiche) is occasionally seen in artificial ponds in which the carp have been heavily fed with cereals (corn and lupines). The calcium con- tent of the bones of such fishes does not differ from the normal.” Schaperclaus’® describes two carp which had several of the anatomical characteristics of knothead carp. They were found among a population of older carp and other fishes which had been fed on barley in a pond free from plant life. The rings of the scales of these two carp showed normal growth during their first year, before they were placed in this pond, and very little growth during their second year, when they were in the pond. Davis and James," of the U. S. Bureau of Fisheries, have made ex- periments showing the effects of deficient diets on carp, and report as fol- lows: “Since the discovery of vitamins by Funk a little over a decade ago, marvelous strides have been made in our knowledge of these elusive food factors, but until very recently we had no information as to their import- ance in the metabolism of lower vertebrates. It was recently found by 44 Klatt, B. Futterungsversuche an Tritonen. Verhandl. d. Deutsch. Zool. Ges. 30 Vers. Jena, Leipzig. 1925. Futterungsversuchen an Tritonen. I. (1926) II. (1927). Arch. f. Entwicklungsmechanik. Vols. 107 and 109. 145 Personal communication from Doctor Scheuring. 16 Schaperclaus, W. Kiemendeckelaufw6lbung bei zweisommerigen Kavrpfen. Fischerei Zeitung. Nr. 24, Bd. 29. 1926. 17 Davis, H. S., M. C. and James. Some experiments on the addition of vitamins to trout foods. Trans. Am. Fisheries Soc. Vol. 54. 1924. —————— THE “KNOTHEAD’” CARP OF THE ILLINOIS RIVER 319 Drummond that trout eggs are very rich in vitamin A while several inves- tigators have shown that cod-liver oil is far richer in this vitamin than any other known substance. The fact that fish tissues contain such large quantities of vitamin A’ is in itself an indication that it must be just as essential to them as to higher animals. However, we had no knowledge of the effect of vitamin deficiency on fishes and in order to supply this want feeding experiments were carried on at the Fairport, Iowa, station for about two months during the summer of 1923. In these experiments young carp from the Mississippi River were confined in troughs supplied with running water and fed diets deficient in one or more vitamins. The results clearly indicate the importance of these accessory food factors in the diet of fishes. In every case there was a high mortality, ranging from 40 to 67 per cent among the fish fed vitamin-deficient diets while there were no deaths among the controls which were fed a diet rich in these substances. The most striking results were obtained with the fish fed a ration con- taining no water-soluble B. After 3 or 4 weeks these fish became very nervous and a number developed convulsions which were especially notice- able whenever the covers were removed from the troughs. During these convulsions the fish would dart rapidly from side to side, twisting and whirling about and striking their heads violently against the sides of the trough. At intervals they would leap some distance from the water until finally, with a last convulsive shudder, the fish would sink quietly to the bottom where they would gradually recover and after a few minutes would swim about in a perfectly normal manner. These convulsions be- came more and more frequent and more intense from day to day until the fish succumbed to the inevitable. Conclusive proof that they were due to absence of B is shown by the fact that in several instances fish which had developed convulsions and would certainly have died if continued on a vitamin-deficient diet were fed considerable quantities of yeast and fully recovered within a few hours. “Fish given diets deficient in fat-soluble A showed no distinctive lesions although the mortality was very heavy. As is well known the absence of A causes a disease of the eyes in rats and other mammals known as xerophthalmia, and its failure to affect the eyes in this case may cause surprise. However, it is generally believed that the xerophthalmia is really due to the fact that the tear glands do not function properly in the absence of A so that the results in this case are, after all, only what we should expect. A deficiency of water-soluble C resulted in high mortality with white spots on the gills caused by the development of necrotic areas.” It seems probable that the reason Davis and James did not find mal- formation caused by the diet deficient in vitamin A (and D) was either that the carp were too old and their growth form was fixed or else that the experiments were not continued long enough for malformation to be- come apparent. 18 Since the publication of this paper, vitamin D has been distinguished from vita- min A, both of which are found in ecodliver oil) D. H. T. 320 I“ttrnois NATuRAL History SURVEY BULLETIN CONCLUSION The knothead malformation of carp described here is believed to be the first known instance of rickets among fishes. Its resemblance to rick- ets in man and other higher vertebrates is as close as can be expected in view of the anatomical difference between a fish and a mammal. Carp may be affected by it from the fingerling stage through life. Their slug- gishness of habit and their retarded growth are further indications of a rachitic condition. These rachitic carp are recognized by the bulging of the opercles, which is often so extreme that respiration is seriously em- barrassed. Rickets in the higher vertebrates is due to a lack of vitamin D in the food, and there is evidence that this is also true in the present case, inas- much as the green aquatic vegetation which supplies vitamin D has been depleted.in the same area and during the same period of time that the carp have been thus malformed. The depletion of the green aquatic vege- tation took place following upon large increases in the sewage load of the Illinois River in the years 1916 to 1918. In the latter year knothead carp appeared, and they have continued up to the present time. They are numerous in the Illinois River from the upper limit of fish life near Utica (Starved Rock) down as far as the Copperas Creek Dam, a distance of about ninety miles. The average frequency of knotheads in this stretch is over 50 per cent, and in certain waters near the upper end it is well over 90 per cent. Other fishes of the area are unaffected, probably because they are less tolerant of pollution than the carp and feed in the cleaner backwaters. The retardation of growth of the knothead carp contributes to the general reduction in yield of the river by pollution, which, in recent years, has probably run into millions of pounds per year, but the present studies give no reason for believing that the value of these carp as food for man is in any way impaired. STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVII. BULLETIN Article IX. Methods and Principles Interpreting the Phenology Crop Pests BY L. R. TEHON PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS July 1928 Reprinted 1931 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol XVIL. BULLETIN Article IX. Methods and Principles for Interpreting the Phenology of Crop Pests BY L. R. TEHON PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS July 1928 Reprinted 1931 ; STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. SuHetton, Director BOARD OF NATURAL RESOURCES AND CONSERVATION A. M. SHELTON, Chairman WILLIAM TRELEASE, Biology JoHN W. Atyorp, Engineering HENRY C. Cowles, Forestry CuHartes M. Tuompson, Representing Epson S. Bastin, Geology the President of the University of WittiaAm A. Noyes, Chemistry Illinois THE NATURAL HISTORY SURVEY DIVISION STEPHEN A. Forpes, Chief aa (Feaoes[eJeounen ScHNEpP & BARNES, PRINTERS SPRINGFIELD, ILL. 1931 59869—800 VOLUME XVII. ArTICLE IX. METHODS AND PRINCIPLES FOR INTER- PRETING THE PHENOLOGY OF CROP PESTS* INTRODUCTION The dominating influence exerted by weather and climate in deter- mining the occurrence and distribution of phytopathogenes and phyto- phages, as well as the extent and the intensity of their attacks, is so con- spicuously self-manifesting that it receives universal recognition ; and much effort has been expended in trying to determine experimentally, with the aid of accurately regulated laboratory devices, the manner in which tem- perature and moisture, the two chief elements, operate. While such work has an inestimable erudite value, much so learned is, at present at least and from the practical standpoint, to a very large extent incapable of being applied to the immediate and pressing problems of the farm and orchard. For this, there appears to be a fair justification; for the investigator, trained to methods inseparable from the microscope, the test tube, and the precision of apparatus and reagent, as well as being greatly restrained by the demands of the varied tasks of teaching and agricultural extension, ean attack this problem only with the resources at his command, and the essential background furnished by an intimate knowledge of the conditions under which organisms exist naturally remains, as a result, unilluminated. Another consequence is that there are few methods known by means of which geographical and seasonal variations, whether in numbers or other characters, exhibited by pests coincidentally with climatic variations or the weather of an environment can be expressed and explained. There is need, therefore, of more extensive and complete knowledge of distribution, of the extent and intensity of plant disease and insect in- vasions, and especially of suitable means to express these things exactly in their relation to climate and to weather. Recently, through the Plant Disease and Insect Surveys of the U. S. Department of Agriculture and similar separate or cooperating agencies in several States, a start has been * The material given under this title constitutes an enlargement and revision of a paper previously prepared but never published, except in an abstracted form (see: Tehon, L. R. The field survey as a basis for the phenological interpretation of the plant disease epidemic. Phytopathology 16: 63. 1926). The term phenology is used so rarely by plant pathologists that I venture to define it, briefly, as the study which recognizes the effects of weather and climate in determining the time of appearance of phenomena, or events, in nature and seeks to define their influence exactly. [321] 322 ILLinois NaturAL History Survey BULLETIN made with the first task; and the ultimate value of their accomplishments will depend not merely upon the success with which they record distribu- tion, but (as it seems to the writer) more particularly upon the progress they make with the second task, by measuring and reporting, in under- standable and comparable terms, periodic and seasonal fluctuations in abundance and intensities of attack. The third task, that of relating these phenomena to their particular meteorological accompaniments, naturally will fall to the investigator, who, by being employed expressly for the purpose or urged thereto by his personal inclinations, finds the time and means at hand to solve these intricate problems. In the present state of affairs, this paper proposes primarily to call attention to a method of defining the relations of plant diseases to climate and weather; but it intends, also, to make additional suggestions which may be useful to entomologists (the latter having used the method to a limited extent) and to point out some of the fundamental principles con- cerned. If certain sections of the paper should appear to readers to be lacking in conclusiveness, the writer would respond that his aim has been not so much to draw final conclusions as to illustrate the potentialities of a method. GRAPHIC DEPICTION OF CLIMATE AND WEATHER The device* here used to depict climate and weather is not new, for it appears to have been originated by Ball (2) about 1910 and to have received its first application to practical problems in the hands of Taylor (17) in 1916; but certain of its meanings are newly shown in the latter part of this paper. Being concerned with temperature and rainfall, it has been termed a hythergraph. A variation of it, which makes use of tem- perature and relative humidity, is known as a climograph, for the reason that relative humidity, resulting from the influence of light, wind, and other lesser factors, as well as heat and rain, is considered to be a more exact expression of climate; but, as records of relative humidity often are not readily available, it can not be used with the same facility as the hyther- graph. By referring to Figures 4 and 5 (pp. 327 and 328), both of which are simple and typical examples, the hythergraph will be seen to be nothing more than a graphic diagram, its vertical scale customarily representing temperature and its horizontal scale rainfall; and any given combination of measurements relating to these elements will be shown thereon by a point located at the intersection of the proper ordinate and abscissa. As a result of the ways in which it can be constructed, this graph will assume one or the other of two general forms, both of which are used in this paper. The simpler form consists of a series of points which mark combinations of temperature and rainfall for successive days or for longer * An interesting discussion, with suggestive notes, is contained in an article by V. E. Shelford, with the title “Physiological life histories of terrestrial animals and modern methods of representing climate’, which occurs in the Transactions of the Illinois State Academy of Science, vol. 13, pp. 257-271, 1920. Ss INTERPRETING THE PHENOLOGY OF Crorp PESTS 323 periods; and the general trend from one to another of these points often is shown by connecting lines, according to Ball’s suggestion, as has been done in Figure 5. In constructing the more complicated form, a considerable number of mean temperature—total rainfall combinations for stated periods, such as months or years, or for localities or regions, are plotted in the manner illustrated by Figure 15 (p. 337); and the particular range of the condi- tions associated with a given phenomenon, or with certain degrees of its manifestation, as indicated by correlative data, then may be determined by joining the plotted points with straight lines. The result is usually one or a number of irregular polygons, which may be made more inclusive, and probably more indicative, by “smoothing”’ them by the use of mathe- matical formulae or, as frequently may be “done with entire satisfaction when data are abundant, simply by applying the draftsman’s ‘French curve” and making the lines indicated by it. The two types of graphs often may be combined advantageously, as in Figure 14 (p. 336), to show not only the ranges but also the trends of months, seasons, or other desirable periods associated with a given phe- nomenon ; indeed, the variations of which the hythergraph is capable are so diverse that they provide almost unlimited opportunities for comparing correlative facts and so of drawing therefrom inferences relating to a wide scope of inquiries. For the sake of simplifying the language in the subsequent pages of this paper, I am suggesting two new terms, namely, thermohyet and thermohyetic, the former to designate a combination datum consisting of a record of temperature and of rainfall (and, by eeaey any point placed on the hythergraph to represent such a datum), the latter to serve as an adjective replacing generally such unwieldy terms as “temperature—rain- fall”, ‘mean temperature—total rainfall”, and the like. It is obvious that the noun can be used only within strict limits; but the adjective often can be used somewhat loosely, at the same time expressing the thought with sufficient clearness, or if it is desirable another word, thermohy etics, may be used also with a looser meaning. WEATHER IN RELATION TO THE LATE BLIGHT OF POTATOES As a first illustration of the use of the graphs described in the fore- going section, the relation of the late blight disease of potatoes to weather furnishes a simple and striking example, not only because the influence of weather upon the occurrence of severe epidemics is so universally recog- nized but also because numerous attempts, ranging from the statement of opinions based upon experience (which are by no means in agreement, superficially) to a graphical presentation of facts, have been made to ex- plain specifically the connection between the two. Without attempting to furnish either an extensive citation list or an adequate review of the literature pertaining to this subject, most of which 324 ItLtinois NATURAL History SURVEY BULLETIN would be entirely outside our problem anyway, we proceed immediately to the work of Martin (13) in New Jersey, who gathered data showing the variation in severity of the annual late blight epidemics in that State for many years and indicated their relations to the rainfall and average tem- peratures of the Julys of their respective years by showing graphically how far, in each case, the thermohyetic conditions departed from the normal July weather. The conclusion of Martin’s work, though in several re- spects illuminating, was in the main lacking in definiteness, in part be- cause the data, in the manner in which they were presented, applied only to New Jersey, and in part because the graphical method he employed was essentially a correlation graph, from which, because the location of the axes of correlation had been predetermined erroneously as lying along normals of temperature and rainfall for New Jersey, the scientific deduc- tions usually expected in such a case could not be obtained. intgate F’ MY Rainfal/ Fic.1. Hythergraph for potato late-blight. The areas labeled A, B, and C mark the thermohyetic con- ditions conducive to severe attacks, mild attacks, and an absence of blight, respectively, as shown by Mar- tin’s New Jersey data. The points indicated by D are for northern Illinois, where blight occurs but rarely; and E is the thermohyet for East St. Louis, where blight never occurs. After restating Martin’s data, so that they appeared as measurements of actual temperature and rainfall instead of departures from normals, it was possible to construct from them the hythergraph shown in Figure 1, in which, as directed in the foregoing section, the polygons resulting from Martin’s data have been smoothed to include all the probable combinations of temperature and rainfall likely to result in heavy attacks of blight (4), in light attacks of blight (6B), and in an absence of blight (C). It is not to be supposed that these three areas on the graph show in- controvertibly the precise limits of the thermohyetic combinations required for these respective grades of blighting ; indeed, the overlapping of the region labeled C upon both the regions A and B indicates a fault in the we bo or INTERPRETING THE PHENOLOGY OF Crop PESTS data which would be even more apparent if the points plotted from the data to delineate the regions 4 and B had been retained; yet for this ap- parently serious discrepancy the only explanation that needs to be made is that the type of disease data, and the sources drawn upon for them, rendered it exceedingly difficult for Martin to make unfailingly correct classifications of his yearly records. Still, some sort of test of the general applicability of this diagram can be made by introducing and comparing observations on blight occur- rence in another region; and because of my familiarity with Illinois, I have made this test by using facts relating to late blight in this State, where there are two main regions in which potatoes are grown and in which the late blight disease would be the source of serious economic loss. The first lies in the southwest, ina rather extensive territory about the city of East St. Louis, and the second, ranging throughout the northern fourth of the State, occupies especially the north tier of counties. In the East St. Louis region, late blight never has been known to occur; but in the north, particularly in the northeast, in McHenry County, it sometimes oc- curs in mild epidemics, though here too, as a rule, it is absent. It is of interest, therefore, to see what relation the thermohyetic con- ditions that exist in these contrasting localities in Illinois just previous to potato harvest bear to the areas marked on our diagram. The large dot, marked £ in Figure 1, represents the average weather for this period at East St. Louis, and, from the position of this point on the diagram it is readily inferred—indeed, it seems quite self-evident—that the usual tem- perature-rainfall complement jor this region differs so much from that required by the late blight disease for its development that only in the most unusual years could this disease be expected to occur there; and, though it should, by chance, occur, its becoming either an extensive or a destructive epidemic is too remote a possibility to admit of consideration. The northeastern region of Illinois presents, however, a different situation, and one which agrees with the facts observed. The series of points marked D on the diagram represent the normal thermohyetic condi- tions during the period when late blight develops for six stations in this region. In accordance with Martin’s data, and with the observed fact that late blight usually does not develop here, the points all fall within the area marked C, the characteristic of which is that the combinations of temperature and rainfall contained by it are not productive of late blight epidemics. By inspecting the diagram, one readily sees, however, that the normal conditions, in the case of four of the northern Illinois stations, lie quite close to the boundary of the area B, defined by Martin’s data, and that only slight variations in temperature and rainfall during the critical period could move these points, for a season, into the area B; and when this oc- curs (as has been observed to be the fact) the development of a late blight epidemic is not only possible, but is, indeed, to be expected. 326 ILLInoIs NATURAL History SurveEY BULLETIN Fic. 2. Regions in which sugarbeets are infected with “curlytop”. (Compiled from data by Ball and by Haskell and Wood.) KX S QO 2 oe SAO ESKKQO RRR Fie. 3. “Range of the beet leafhopper. Widely spaced cross hatching shows the probable natural breeding range, and the closely spaced cross hatching marks additional breeding spots from which consid- erable migration occurs. (Redrawn from Ball.) INTERPRETING TUE PHENOLOGY or Crop PESTS 327 THERMOHYETICS OF THE BEET LEAFHOPPER AND SUGAR BEES GUMIEY TROP? “Curlytop” of sugarbeets, a virus disease carried and disseminated by the beet leafhopper, Eutettix tenella Bak., is known to occur in epi- demic proportions only in the western and drier regions of the United States, where, according to Ball (1) and Haskel and Wood (8), it has been recorded definitely in the regions shown in Figure 2; but the leaf- hopper, being by no means locally restricted to these regions, ranges over the very extensive territory indicated by the diagonal lines in Figure 3, 1, Se) he pe (OETA ASO) GEE Rainfall Fic. 4. Normal thermohyetic limits of the geographic ranges of the beet leafhopper and the “curlytop” disease. supposedly breeding successfully throughout as much of the southern part of its range as is shown (after Ball) by the more widely spaced cross- hatching, but breeding and migrating in large numbers , from the regions designated in the figure by the more closely spaced cross hatching. From the records of Weather Bureau Stations situated in representa- tive regions, one may draw a composite picture, in terms of monthly aver- age total rainfall and normal temperature, of the year-long thermohyetic conditions which the leafhopper and the curlytop disease find suitable. The outer line in Figure 4, represents the outer limits of the annual varia- 328 ILtinoris NATuRAL History Survey BULLETIN tions in the thermohyetic conditions associated with the geographic region throughout which the leafhopper ranges; but records from weather sta- tions located in the neighborhood of curlytop-infested regions all fall with- in the inner line and give a diagram strikingly different in shape and much less extensive. Thus is it shown that the thermohyetic conditions per- mitting the occurrence of the disease are very definitely circumscribed as compared to those controlling the leafhopper’s migratory range. This very evident difference between the conditions that favor the insect and those that favor the disease may be illustrated in a more par- ticular manner by comparing in Figure 5 the trend of the normal monthly thermohyets of a locality in which only the insect abounds with those of a locality where both insect and disease occur, the localities represented being El Paso, Texas, and Merced, California, respectively. Since the disease appears only in the summer months, the upper part of diagram B defines particularly the thermohyetic conditions necessary for its occur- LF UWP LE BD BAS Ftaintal/ Fie. 5. Comparison of the month- ly thermohyets and annual trend for El Paso, Texas, A, which lies in the 7 7 7 * 7 range of the leaflropper only, and 2: Aoi LS" 20" 25 Merced, Cal., B, where both the leaf- ainfall hopper and “curlytop” occur. The Fic. 6. Monthiy thermohyets for summer season is very dry where 1921 (A) and 1922 (B) at Burley, “curlytop” abounds, but the leaf- Idaho. This locality, which lies hopper can thrive in a region where within the range of the beet leaf- an appreciable amount of summer hopper was infested by “curlytop” rainfall occurs. in 1921, but not in 1922. INTERPRETING THE PHENOLOGY OF CRroP PESTS 329 rence; and there is a decided contrast with those under which the leaf- hopper alone thrives, the difference apparently being a matter of summer rainfall, as a practical absence of precipitation at this time seems neces- sary for the disease. Outbreaks of curlytop occur, rarely and at long intervals, in unusual situations, last a single season, and then disappear. Such an instance oc- curred at Burley, Idaho, in 1921. A hythergraph for that locality, giving the monthly thermohyets for that year in comparison with those for 1922 (normals are not available), is shown in Figure 6; and the difference be- tween the two diagrams emphasizes again the connection between dryness and disease incidence, the absence of rainfall during July being a distinct- ive characteristic of the year of disease. The fact that the July rainfall in 1922 exceeded that of the previous year only by slightly less than half an inch gives additional weight to a common observation, ‘namely, that in nature what appear to be exceedingly slight differences in habitat serve effectively to predetermine the successful existence of an organism. In many regions, both the leafhopper and the disease occur every year, the disease varying in severity and the leafhopper in numbers from year to year. So far as recorded information goes, it seems to be rather generally true that a year of severe disease is also a year of abundant leaf- hoppers. From the weather records for the years of severe disease in such a region, one would expect consequently to obtain a hythergraphic representation of the thermohyetic limits favorable to both the disease and the leafhopper. Such a diagram, smoothed, for Fresno, California, is given in Figure 7. One would expect the normal thermohyets of other regions to fall within this diagram, and the probable truth of this expectation is shown also in Figure 7, in which the monthly normal thermohyets for Sacra- mento and for southern California as a whole are inserted and actually fall within the smoothed or generalized diagram. On the other hand, the hythergraph of a locality unsuited to both the insect and the disease ought not to conform in any important respect to the smooth diagram which represents the thermohyetic characters of the normal habitat: and this is demonstrated by the hythergraph for the year 1922 at Burley, Idaho, su- perposed in Figure 7, which shows not only a striking inconfor mity of trend but also a series of monthly thermohyets falling, with 3 exceptions, entirely outside the natural range of the insect and the disease. Although abundance of leafhoppers and severity of disease usually are coincident, they need not be always so; and one is led to surmise from this that there are certain thermohyetic conditions that have a special in- fluence upon disease incidence while certain others determine insect abun- dance. The growing season of the crop, the characteristics of which have been noticed already, is undoubtedly the period of the year most influen- tial with respect to the disease, whereas other periods of the year may be of greater significance with respect to the leafhopper ; and it seems likely that the abundance of the leafhopper, while dependent in some measure upon the weather of spring and summer, probably is influenced to the ILLino1is NATuRAL History SurRvVEY BULLETIN Sacramento, Cal, normals. 5.Cal normals. ae 4" Rainfall Fic. 7. The annual thermohyetic limits of regions in which “curlytop” is severe include the normal thermohyetic condi- tions of a locality (Sacramento, Cal.) and of a region (south- ern California) where the disease is normally abundant but do not include or conform to a locality (Burley, Idaho) where the disease rarely occurs. ~ January | 1” pt ; 3" 4" ie Rainfall Fic. 8. In the Lake Tulare region of California, the thermo- hyets for January and February preceding seasons of leafhop- per abundance fall in the warmer and wetter ranges of these months, as indicated by the location of the triangles with re- spect to the normal thermohyets shown by the circled dots. INTERPRETING THE PHENOLOGY OF CRoP PESTS 331 greatest extent by that of the hibernating or resting period. The range of weather for this period in years of insect abundance is shown by months in Figure 8 for the Lake Tulare region in California, a typical hibernating locality which supplies an abundance of the leafhoppers to surrounding territories during favorable years. When the corresponding normal thermohyets for the same region are indicated on the hythergraph, it be- comes apparent that the thermohyetic conditions of January and February in years of leafhopper abundance lie definitely within the wetter and warmer ranges of those months. THERMOHYETICS OF THE CUCUMBER BEETLES AND THE BACTERIAL WILT OF MELONS The peculiar interdependence of the cucumber beetle, Diabrotica vittata Fab., and Bacillus tracheiphilus (EFS) Stey. in the production of the bacterial wilt of cucurbits affords an unusually good opportunity to show how the thermohyetic characters of the natural habitat may be de- termined and how its variations influence in greater or less degree the ac- tivities of the organisms concerned in so complex a relation. Muskmelons and the other members of the plant family Cucurbi- taceae, excepting only the watermelon, are subject to a wilt disease which results from the pathogenic activity of Bacillus tracheiphilus (EFS) Stev. In pure culture, and under the exacting conditions imposed by the bac- teriologist in his laboratory, this microbe shows a marked sensitivity to temperature, its minimum requirement for growth being 46° F., its opti- mum lying between 77° and 86°, its maximum temperature for growth being 95°, and its thermal death-point lying at 110°. Within its host, it lives only in the xylem ducts of the water-conducting tissue and, unless it can gain access to them immediately after being introduced into the plant, it is not able to cause wilting. It is this peculiarity that brings cucumber beetles into the problem; for they serve as carriers of the bacterium, and the punctures they make while feeding afford a means of entrance for the bacterium, directly from their mouth parts or indirectly from their droppings, into the xylem ducts. The only known place in which the bacterium overwinters is the digestive tracts of the beetles. Experimental evidence shows that both the striped cucumber beetle (Diabrotica vittata Fab.) and the 12-spotted beetle (D. duodecempunctata Say) act as carriers of the bacterium; but field observations indicate that the striped beetle, which is the more abundant of the two in ordinary sea- sons, is the chief carrier. The principal sufferers from the wilt disease are the muskmelon and its cultural modifications, the cantaloupe and the Honey Dew melon. The distribution of these crops is indicated in Figure 9, which shows the ap- proximate location of farms reporting 1 acre or more in the 1910 Census. Unfortunately, later data are not available; but the reports of the U. S. Department of Agriculture, through its Bureau of Agricultural Economics, i) bo Ittinois Natural History Survey BuLietry Fic. 9. Distribution of melon crops subject to bacterial wilt. Each dot represents 50 acres grown in 1909. (Redrawn from Finch and Baker’s Geography of the World’s Agriculture. ) Fic.10. Range of the striped cucumber beetle. (Redrawn from Chittenden.) 9 INTERPRETING THE PHENOLOGY OF Crop PEsTs 333 indicate that the distribution of the crop has not changed greatly since that time, although the acreages have changed considerably in several states, and the map will serve to indicate where the disease and the beetles may be of economic importance. Data showing exactly the limits of distribution for either of the cu- cumber beetles are not available. Chittenden (3) gives the distribution of the striped beetle as the entire eastern two-thirds of the United States. illustrating his statement with the map reproduced in Figure 10; and the belief prevails among entomologists that there is virtually a coincidence of distribution for the two species. A search of literature and an exten- sive correspondence have failed to indicate that either beetle occurs outside the North American continent, though both apparently range northward into Canada and southward into Mexico. Throughout this territory the average rainfall is 20 inches or more per year. Brod Fic. 11. Broad ranges of the striped cucumber beetle. This map is drawn from data in publications and from information secured by correspondence. The general effect of temperature upon the striped beetle is most readily seen in connection with the number of broods which it produces per year. Throughout the northern part of its range, there is but one brood, while southward the broods increase to two and exceptionally three, and at times there may be as many as four in extreme southern Texas. The approximate geographic limits of these brood numbers are indicated in Figure 11 by the wavy horizontal lines, and it is, perhaps, not altogether an unexpected coincidence that these brood lines pretty definitely follow certain isotherms indicating mean annual temperatures. Where the mean temperature is annually less than 55° F., the brood number is constantly one; between 55° and 60° there is one brood and usually a partial second; between 60° and 65° there are generally two broods ; between 65° and 70° there are two broods and sometimes a third; and where the annual mean temperature exceeds 70° there may be four broods in a year. 334 InLtinois NAtTuRAL History Survey BULLETIN The available data on the occurrence of the bacterial wilt of cucurbits show it to be prevalent through a large part of the United States and to have occurred, at least in isolated instances, in Canada, Germany, Russia, the Transvaal, and Japan. The Canadian records can not be verified; the report from Russia is based upon a single wilted plant found in a green- house; those from Germany, the Transvaal, and Japan appear to be au- thentic, but are not accompanied by any statement as to the presence or absence of the cucumber beetles as carriers ; hence it is apparent that these records of occurrence outside of the United States can not be made the basis of a world-wide study. But records within the United States since 1918 are sufficiently complete to be fairly satisfactory. All of the states from which the disease has been reported since that year are shown by Fic.12. Distribution of cucurbit wilt in the United States, compiled from Plant Disease Survey Reports. Diagonal lines mark the States from which this disease has been reported authentically, and cross hatching marks the region from which reports of severe wilt usually come. the hatching in Figure 12, while those states in which the disease is com- monly reported as serious are indicated especially by the cross hatching. Probably the disease, though present, is not a serious menace to the com- mercial crop throughout all of this territory, nor even throughout the territory in which it is commonly reported as being severe; rather, the regions of severity are probably rather localized and could be ascertained with fair accuracy by comparing Figure 9 and Figure 12. Although the bacterial wilt has a distribution in the United States practically coextensive with that of the striped beetle, the territory through- out which it is most severe lies in a latitude ranging generally north of the southern boundary of Tennessee, while the territory in which the beetle appears to be most successful, as indicated by the number of generations INTERPRETING THE PHENOLOGY oF CROP PESTS 335 per season, lies to the south of this line. The extent of the wilt’s range is not limited northward in the United States, but the disease rarely is found in epidemic proportions much farther north than the southern third of Wisconsin. To the southward, it is limited, unless in exceptional cases, by the increase in temperature during the summer months. Certain thermohyetic characteristics of the coincident ranges of the beetles and the wilt are expressed hythergraphically in Figure 13. For convenience, in this case, the two halves of the year have been separated, = ae, Fj Rainfall Fig. 13. Thermohyetic range, month by month, of a normal year for the coincident range of the striped cucumber beetle and cucurbit wilt. Circled dots show normal monthly thermohyets for selected States, and the months are indicated by numbers. and the thermohyets for certain States for each month of the year have been plotted, the outer points being connected by inclusive lines. As this represents graphically the actual thermohyetic conditions reported by the Weather Bureau, it, of course, is not to be understood as showing the only conditions under which either the beetles or the wilt «can exist, but is to be considered as an inclusive statement of the average weather con- ditions prevailing in the territory in which these organisms occur. It is 336 Ittinois Natural History Survey BuLLEeTIN probable that a closer approximation of the limits of habitable climate for these organisms can be obtained by regarding the individual points for each month, as lying in undetermined ellipsoids and then connecting them by curved lines, thus substituting the rotund diagrams for the irregular polygons of Figure 13. Such an arrangement, shown in Figure 14, ought to be considered a reasonably comprehensive statement of the ranges, month by month, of the thermohyetic conditions under which the cucum- ber beetles and cucurbit wilt can exist successfully. As was pointed out, the geographical limits of severe wilt are by no means as extensive as the territory throughout which it and the beetles range. It is usually severe in the region in which the beetles generally have one to two broods per year, tending to be less so both to the north and the south. By arranging reports on wilt, secured from the mimeo- graphs of the federal Plant Disease Survey and by special correspondence, into the five general classes, light, mild, destructive, moderately destruc- tive, and severely destructive, I have found it possible to construct a hy- _ thergraph, using annual means of temperature and annual totals of rain- fall for the regions and the years in which these degrees of disease were 3} ” Ratnfall Fic. 14. Smoothed hythergraph drawn from Fig- ure 13. The numbers indicate the months. ee Se ee ee - INTERPRETING THE PHENOLOGY OF CRoP PESTS 33 reported to have occurred. In the resulting graph, given in Figure 15, the outer range of thermohyetic combinations, marked dA, includes those conditions under which the wilt occurs in light form; the thermohyetic limits bounded by the line marked B include regions and years character- ized by mild wilt and usually 1, 3, or 4 broods of beetles per year ; within the limits marked C, the wilt is generally destructive, and the number of broods of beetles is either 1, or 1 to 2 per year; and the line marked D in- closes indubitable records of moderate and severe destruction. The dif- ferences in temperature and rainfall which distinguish these limits on the dry side of the graph are wide at first, but decrease as the intensity of disease attack increases ; and the very slight difference between the limits B and C may be taken to indicate that at this point even very small changes in thermohyetic combinations affect very greatly the intensity of the wilt attack. As it is possible to be more specific regarding the wilt in Illinois, I give the following generalized comparison of the destructiveness of this dis- IO 2b 3G. Fo 0 FiatnFatl Fic. 15. Mean annual thermohyetic ranges under which various intensities of cucurbit wilt develop. In the region marked A, the wilt occurs in light form; in B, it is mild but heavier than in A; in C, usually destructive; and in D, moderately to severely destruc- tive. InLinoris NAaturAL History SuRVEY BULLETIN Fi\Raintal/ in inches| F°\ Rainfal/ iz inches \ F°\ Kairfall in inches 2 3 4 Ss 60 ae JZ 4 Ss Ce 4 A a SEE 60 Fic. 16. Hythergraphs for Illinois, showing the monthly thermo- hyets for a normal year and for the years 1922-1926. The normal year falls near the 3-inch rainfall coordinate; but the year 1922, when bac- terial wilt was most severe, falls near the 4-inch coordinate. The suc- ceeding years, in which wilt was progressively less severe, fall more and more toward the dry side of the graph. ee ee ee ee Oe INTERPRETING THE PHENOLOGY OF CRoP PESTS 339 ease, as determined for the State by our field examinations, using the same terms of distinction as above. Year Destructiveness of Cucurbit Wilt 1922 Moderately destructive 1923 Destructive,or moderately so 1924 Mildly destructive 1925 Light to mild 1926 Light A fairly steady decrease in abundance has occurred since 1922, the minimum being reached in 1926. This is due, in part, to a more general use of an efficient beetle control during the last three years; but as the beetles were still abundant in many untreated fields, the difference is not attributable wholly to this cause. A comparison of the normal hyther- graph of Illinois and hythergraphs for the years 1922 to 1926, inclusive, these being shown in Figure 16, reveals marked differences in the thermohyetic trends of the years and in the monthly thermohyets—differ- ences which are progressive and which correspond to the decrease in amount of disease by moving uniformly toward the dry side of the graph. The normal year, in IMinois, lies close to the ordinate marking 3 inches of rainfall. The 1921-1922 season, with destructive disease, falls roughly about the 4-inch i eae although it shows a great fluctuation from this average during most of its months. The year 1922-1923 rather close- ly approximates the normal, falling quite near the 3-inch line; 1923-1924 lies still farther to the dry side of the diagram, especially in the spring months; and the year 1924-1925, with the exception of the summer, lies very close to the dry side, falling practically on the 2-inch rainfall line; while the year 1925-1926, which is not greatly different from a normal year, bears out the rule. SIGNIFICANCE OF HYTHERGRAPHS Hythergraphs such as I have used as illustrations in the preceding pages have been employed in a number of instances* to indicate habitats and probable habitat ranges for various organisms. Originally devised by Ball in 1910, and first used by Taylor in 1916, they have been used since by Pierce in connection with insect life histories, by at least two per- sons to suggest the geographic ranges of insects, and by Huntington as the basis of an analysis of the relation of climate and weather to human health and progress. But none of these workers analysed the meaning of their graphs further than to draw such conclusions as were apparent upon inspection of the completed charts. It should be expected that diagrams such as these, which appear to offer exceptionally plain evidence of the dependence of organisms upon climate, and of the marked limitations placed upon organisms by variations in thermohyetic conditions, would be founded upon certain natural laws, or have such a close relation to them that sufficient study would’ reveal some basic facts regarding all habitats. *See the appended bibliography. 340 Intinois NaturAL History Survey BuLLEeTIN As it is used now, the hythergraph takes two forms. As they seem to be distinct, both in their construction and in their use, so each has its own significance in interpreting biotic phenomena. The first type, exemplified in Figure 16, shows diagrammatically the progress, from one month to another, of individual or grouped thermo- hyets attending any given phenomenon. Beyond the fact that it pictures conditions more simply and clearly than words, and so makes comparison easy, it has no significance. The second type is represented especially in Figure 15. In its con- struction, a considerable number of thermohyets are plotted in such a way as to indicate, when they are sufficiently numerous and accompanied by good correlative data, what specific conditions govern, or are related to, the occurrence of definite phenomena. When such a diagram has been completed, it is usually true that the thermohyetic conditions productive of successive degrees of phenomenon development, such as amounts of disease, healthiness, and the like, can be defined quite exactly by con- necting in series the plotted thermohyets in accordance with the correl- ative data. The resulting lines, called “isopracts’’ by Huntington, are roughly circular, elliptical, or ovoid, and usually are eccentrically arranged. These relations may be illustrated concretely with data and a modifi- cation of a diagram which I have used in another connection (20). As the result of careful surveys of wheatfields in Illinois, numerical indexes showing the destructiveness of leaf rust (Puccinia triticina Erikss.) were obtained for each of five years, with the intention of determining from them what relation the yearly mean temperature and the total rainfall bore to the intensity of the rust attack. The data at hand were those given in the following table : Year Destructiveness Mean temperature Total rainfall of index of the rust years the rust years 1922 50.3 54.8 41.73 1923 31.3 53.1 32.69 1924 19.1 51.9 38.74 1925 ileal 53.0 31.15 1926 11.2 51.3 35.15 Neither by inspecting the table nor by employing the usual graphic methods can one demonstrate the relation that actually exists between the rust indexes and their accompanying thermohyets; but it can be demon- strated by the hythergraphic method with the diagram given in Figure 17. In constructing this diagram, a preliminary graph was made, upon which were plotted the thermohyets for each index of the rust; and, as these seemed to fall into two well-defined series, the trend of each series was marked by a dotted line. The relative values of the temperature and rain- fall scales were then adjusted by the simple expedient of redrawing the INTERPRETING THE PHENOLOGY OF Crop PESTS 341 dotted lines at 45° angles to the axes and then locating on them the points on the old lines by swinging intersecting arcs with a compass. The result was such as to indicate that a difference of 1° of mean annual temperature would equal, in its effect, an approximate difference of 5 inches in total annual rainfall.* Having thus located the trend lines, and having replotted the thermo- hyets accurately, as they are shown in Figure 17, I could readily see that the trend lines lay one on each side of the line of perfect correlation. But neither in the data nor in the graph is there any indication of the probable location of this line or of the line of absolute non-correlation. It seemed to me reasonable to suppose, however, that, as Illinois appeared to be fairly representative of the rust’s habitat, these lines ought to have some rather close relation to the normal thermohyet for that State; and this thermohyet, therefore, I plotted at the intersection of the normal mean annual temperature line of 52° and the normal total annual rainfall line of 36.42 inches. Through the point thus located, I drew tentative lines of correlation and non-correlation; and, by good fortune, I found the = = Fe | SSF 56 Peel ly Vig IS 52 5/ | —30" as 0a OC 60° Rainfall Fic. 17. Hythergraph indicating the relation of the intensity of wheat leaf rust attacks to annual thermohyets in Illinois. The method used in constructing this graph is described in the text. *It appears from a hythergraph given by Griffith Taylor on page 271 of his “Environment and Race” (Oxford University Press. 1927), that survival of infants in Australia—the converse of increase in prevalence and fatality of infant dis- eases—increases as both temperature and rainfall decrease but Taylor has not de- termined the relative effects of the two elements. 342 ILLInoIs NATURAL History SuRVEY BULLETIN latter passing so near the point D, which had a predetermined rust index of 17.1, and cutting the lower trend line at H—which appeared upon in- spection to lie very close to the point where, between E and C (which had determined indexes of 11.2 and 19.1, respectively) one would expect to find an index of 17.1—that I took this to indicate with fair certainty: first, that my hypothetical line of non-correlation lay so close to the real line as to serve the same purpose; and, secondly, that the line of true corre- lation must consequently be situated parallel to the two trend lines and very nearly midway between them. I, therefore, replaced the tentative correlation line, which at first I had drawn through the normal Illinois thermohyet, with another (F-G in the figure) and proceeded to locate all given rust indexes not only on the trend lines but also on the correlation line in accordance with the following reasoning. It seemed clear to me, in view of certain other data I had at hand, that the rust fungus might very well be regarded as having physiological properties similar to those long since proved for other organisms and that if I followed, deductively, for my organism the same steps as had been traversed experimentally for others, I ought to arrive at a tenable, though necessarily quite general, hypothesis of thermohyetic relations. I con- sidered, therefore, that if a complete correlation between increasing tem- perature and increasing rainfall, singly or in combination, and disease in- crease were assumed to exist throughout all ranges of temperature and rainfall, the graphic expression of such a condition would be a straight diagonal line of the general formula yk», when y represented increase in disease and x increase in either temperature or rainfall or both. With this assumed, it is apparent that all the various combinations of temper- ature and rainfall capable, when acting together, or producing a given amount of disease would be shown by a rectangular hyperbola of the gen- eral formula ry=k?. Of course, it has been determined experimentally many times and for a great diversity of organisms that, though appearing to be true within a limited range of conditions, no such fine regularity as the above exists. Instead, we have come to expect in place of the straight diagonal, a curve which rises slowly at first, then rapidly and quite regularly through most of its length, until it reaches an optimun and thereafter falls precipitately to a maximum. Such a curve often has no definite formula, though its type is usually indicated as y=f(«). The rapidly rising’ portion of this curve, though approximating the straight-line diagonal, never conforms to it completely ; for there is continual readjustment throughout its length to the increasing, decreasing, and inhibiting effects of the changing en- vironmental factor. Consequently, the curve for a constant amount of disease, when plotted with temperature and rainfall as the axes, can not be a rectangular hyperbola; for, when the amount either of temperature or of rainfall becomes inhibitive, that effect must be counterbalanced by the addition, upon the curve, of an increasing effect from the other; and the curve, though approaching the hyperbola in its mid-region, is made, toward its extremities, to swing away from the axis. The result is an A i a a ES ee INTERPRETING THE PHENOLOGY OF Crop PESTS 343 ellipse of the type to which the general formula aa + by? + cry + dx + ey + f =o usually applies. Returning then, to my rust problem, I was confident that all the points denoting any given amount of rust attack ought to lie in an isopract of an elliptical or ovoid shape, the long axis of which would be the line of per- fect correlation; and, having demonstrated the position of this line as midway between the trend lines, I saw that for every themohyet of known rust value I could determine geometrically two other thermohy ets having, hypothetically, the same rust value, one upon the opposing trend line and one upon the correlation line, for I could measure by running a line from a thermohyet of known value to the junction of the correlation axis, an angle which would determine the position of another line drawn from this junction to cross the other trend line at a point geometrically equivalent to the first and, with two such points located, r could determine their equivalent upon the correlation line by marking the point where it and their respective temperature and rainfall values coincided. By this means, I was able to increase my original five points of data to fifteen, having three points to denote the location of the isopract for each of five known rust indexes, and, after drawing a large series of partial ellipses through each of these five sets, I selected from each series the one which in con- junction with all the others, seemed most apt to fulfill the conditions im- posed. It is not to be supposed that I considered these isopracts, so hypo- thetically constructed, as by any means proved; yet the verisimilitude be- tween the chart thus developed and the hythergraphs so readily obtained with more abundant but less accurate data, together with the fact that all the requirements of natural processes appeared to have been satisfied, led me to believe that I had obtained a clear, though general, picture of the relation of rust to annual thermohyetic conditions and that I had, at the same time, shown why hythergraphs similar to Figure 15 do indicate so clearly the limitations imposed by climatic conditions upon the occur- rence and distribution of organisms and the influences of fluctuations in weather upon the success of an organism in a given region. The ellipses, or isopracts, of an hythergraph, since they usually mark measured degrees in the manifestation of some natural phenomenon, are comparable to the contour lines used by physiographers to show differ- ences in altitude on plane-surface maps. Indeed, to carry the physio- graphic comparison still farther, the hythergraph may be regarded as a representation, in a single plane, of three of the factors which enter into the composition of a natural phenomenon; for the flat surface has width and length, and the isopracts show height. Though two distinct ele- ments, temperature and rainfall, are shown by the flat surface, their re- ative values, with respect to the third dimension and to each other, can be determined readily by means of correlation charts and graphs, and the two scales can be arranged in units of equal value; that is, with a series of increases in one element there must be corresponding increases in the other, and a plotting of points resulting from these increases should deter- 344 Intinoris NaruraLt History Survey BuLLeTin mine a line lying at an angle of exactly 45° from either the abscissa or the ordinate.* Because they are considered to have a definite relation to the adjusted factors denoting width and length, the isopracts should be smooth in out- line and regular in shape; but in practice they often are not so—a fact for which the explanation may be advanced that, as there are other elements, such as sunlight, wind, and the like, acting also, their influence will be shown in the isopracts in much the same manner as the action of wind and water as erosive agents appears in contour lines. This conception of the inter-relation of the weather elements and nat- ural phenomena as a 3-dimensional subject seems to me to be so impor- tant, not only as a basis for understanding and interpreting the effects of weather and climate upon the distribution and abundance of organisms but also as a fundamental law bearing directly upon the results of precise laboratory experimentation, that I have ventured to embody it concretely in the perspective drawing shown as Figure 18. The data from which this figure is formed are the same as those used for Figure 15, except that, in place of the rather generalized terms previously used, I have sub- stituted concrete limits to the amount of disease, designating somewhat arbitrarily the circle A of Figure 15 as having 5 per cent diseased plants ; circle B, 20 per cent; circle C, 35 per cent; and circle D, 50 per cent— thereby providing for every point shown on Figure 15 a datum of 3 items, one of temperature, one of rainfall, and one of disease abundance, by means of which four planes of the cone in Figure 18 were very easily located. The outlines of the cone and the smoothed circumferences of the four planes are, of course, drawn entirely by inference; but it seems to me from this figure that the relating of a natural phenomenon, in all its degrees of manifestation, to any two outstanding factors of environ- ment involves measurements expressible, as a whole, in a three-dimension diagram, the resulting object being conic in form. One characteristic of this cone appears to have a rather important significance when results obtained by experimentation, under controlled conditions, upon the reaction of an organism to an environmental factor are made the basis for predicting any event in nature. The cone is not symmetrical. In profile, it has upon one side an extensive base, which rises slowly, at first almost imperceptibly, from the plain; as the altitude increases, the gradient of the slope also increases, until the peak rounds it off; and, on the other side, the downward slope falls away very steeply and merges abruptly into the plain. The shape of this profile is similar in all respects to the characteristic curve of response that is secured ex- perimentally when one factor is held constant and the other is varied: in- deed, from its shape and composition, it seems apparent that the cone, if cut into an infinite number of longisections, would furnish exactly the same set of curves as would be secured from an equal series of experi- ments. *The proof of this statement would require a recapitulation of a considerable part of the mathematical theory relating to the standardization of measurements, which, though simple, lies outside the scope of this paper and therefore is not given in detail. INTERPRETING THE PHENOLOGY oF Crop PESTS Tem PERA > oye RAT URE YO" 45 eadialin 10 80 Ss) € of diseased plants B SJ ~ S Disease Prevalence: Percenta 0 LP AP APRON EE GeO IO RESO! Rainfall & pe. Fig. 18. Three-dimensional graph indicating the interrelation of an- nual mean temperatures, totals of annual rainfall, and the severity of disease attack. This is a reconstruction of Figure 15. 546 Ittinois NATuRAL History SurvVEY BULLETIN BIBLIOGRAPHY* 1. Bart, E. D. The beet leafhopper and the curlyleaf disease that it trans- mits. Utah Agr. Exp. Sta. Bull. 155. 1917. 2. Baw, J. Climatological diagrams. Cairo Sci. Jour. 4:280-281. 1910. 3. CHITTENDEN, F. H. The striped cucumber beetle (Diabrotica vittata Fab.) and its control. U.S. Dept. Agr. Farmers’ Bull. 1038. 1919. 4. Cook, W. C. Studies in the physical ecology of the Noctuidae. Minn. Agr. Exp. Sta. Tech. Bull. 12. 1923. The distribution of the pale western cutworm, Porosagrostis orthogonia Morr.: a study in physical ecology. Ecology 5:60-69. 1924. — Distribution of the alfalfa weevil (Phytonomus posticus Gill.) A study in physical ecology. Jour. Agr. Res. 30:479-491. 1925. 7. FLaAnpers, V. B. The use of charts and graphs in the study of climate. Mo. Weather Rev. 50: 481-484. 1922. 8. Haske, R. J. Anp Jessie I. Woop. Diseases of vegetable and field crops in the United States in 1926. Plant Disease Reporter. Supple- ment 54: 259. fig. 24. 1927. 9. HuntineTon, E. Civilization and climate. New Haven, Yale University o os == Press. 1915. 10. ———————_ Graphic representation of the effect of climate on man. Geog. Rev. 4:401-403. 1917. 11. ———————World power and evolution. New Haven, Yale University Press. 1919. 12. Jounson, E. L. Relation of sheep to climate. Jour. Agr. Res. 29: 491-500. 1924. 13. Martin, W. H. Late blight of potatoes and the weather. New Jersey Agr. Exp. Sta. Bull. 384. 1923. 14. Prercr, W. D. A new interpretation of the relationships of temperature and humidity to insect development. Jour. Agr. Res. 5:1183-1191. 1916. 15. Suetrorp, V. E. Physiological life histories of terrestrial animals and modern methods of representing climate. Trans. Ill. St. Acad. Sei. 13:257-271. 1920. 16. ————————_ An experimental investigation of the relations of the codling moth to weather and climate. Ill. State Nat. Hist. Surv. Bull. 16:311-440. 1927. 17. TaAytor, G. Control of settlement by humidity and temperature. Common- wealth Bur. of Meteorology (Australia). Bull. 14. 1916. 18. —— Geographical factors controlling the settlement of tropical Australia. Queensland Geog. Jour. 32-33: 1-67. 1918. 19, —————-_ The settlement of tropical Australia. Geog. Rev. 8:84-115. 1919. 20. Tron, L. R. Epidemic diseases of grain crops in Illinois: 1922-1926. Ill. State Nat. Hist. Surv. Bull. Vol. 17 (Art. I). 1927. 21. Varney, B. M. Some further uses of the climograph. Mo. Weather Rev. 48:494-497. 1920. * Citations given here but not mentioned in the text are included in order to furnish suggestive source references to readers interested in weather diagrams. ee ey ee STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVIL. BULLETIN Article X. SE An Account of Changes in the Earthworm Fauna of Illinois AND A Description of One New Species BY FRANK SMITH PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS August, 1928 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVII. BULLETIN Article X. An Account of Changes in the Earthworm Fauna of Illinois AND A Description of One New Species BY FRANK SMITH PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS August, 1928 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. SHeELtTon, Director BOARD OF NATURAL RESOURCES AND CONSERVATION A. M. SHELTON, Chairman WILLIAM TRELEASE, Biology JOHN W. ALyorp, Engineering Henry C. Cowtes, Forestry Cuartes M. Tuompson, Representing Epson S. Bastin, Geology the President of the University of WiitiAM A. Noyes, Chemistry Illinois THE NATURAL HISTORY SURVEY DIVISION STEPHEN A. Forbes, Chief SCHNEpP & BARNES. PRINTERS SPRINGFIELD, ILL 1928 VoLuME XVII ARTICLE X AN ACCOUNT OF GHANGES IN THE EARTHWORM FAUNA OF ILLINOIS AND A DESCRIPTION OF ONE NEW SPECIES* Frank Smith The contents of this paper include additions to the list of species previously recorded from Illinois and also furnish evidence of obvious changes in the earthworm fauna of one locality which are probably simi- lar to changes taking place in other parts of the state. The tendency is towards an increasing domination of European species and a correspond- ing decrease in the abundance of some indigenous forms. There are various records of similar modifications of the earthworm fauna in other parts of the world in which Europeans have settled and in which the European species of LumpBricipAE have to a greater or less extent re- placed the indigenous species. Recent additions to the former lists of European species found in the state include Helodrilus venetus hortensis (Michaelsen), H. chlo- roticus (Savigny), H. octaedrus (Savigny), and Lumbricus rubellus Hoffmeister. Additions to the list of indigenous species include Helodri- lus beddardi (Michaelsen) and H. heimburgeri n. sp. During a period of over 30 years (1893-1927) the writer has been interested in Illinois earthworms and their distribution, partly because of their utilization in some of his instructional work and partly because of using them as objects of research leading to the publication of several papers on the subject. In connection with these activities numerous col- lecting and observation trips have been made in the vicinity of the Uni- versity of Illinois in order to obtain specimens of the various kinds repre- sented and, incidentally, to learn something of their relative numbers and the kinds of situations in which representatives of the various species are most abundant. A comparison of the results of such trips made in earlier years of that period and those near its close shows that some marked changes have occurred. Some kinds found infrequently or not at all in the earlier years have become abundant in some areas in which there has been a corresponding decrease in other species. Increasing irregu- larities of distribution have been apparent which are presumably due to increased numbers of introduced forms which have not as yet had time to become abundant except in restricted areas. * Contributions from the Zoological Laboratory of the University of Illinois, [347] 348 Ittinoris Naturat History Survey BuLLeTiN UPLAND-SOIL SPECIES The collecting and observation trips which involved ordinary upland- soil species have mostly been made immediately after rainfalls when large numbers of individuals of some species were crawling about on the surface or were sheltered under debris of various kinds and especially likely to be found on the sidewalks and aiong the curbing of paved streets. Actual digging for such forms has been restricted to small areas. The lack in the earlier years of a knowledge of the changes in the fauna which were to take place resulted in a failure to make records of dates and of many numerical data which, if available, would have been very useful in the preparation of the present paper. The three species of LumpBricipaeE, listed under other names by Gar- man (1888) as frequent or abundant in Champaign, [llinois, were Helo- drilus foetidus (Savigny), H. roseus (Savigny) and H. caliginosus trap- ezoides (Duges). They were found in similar abundance throughout the whole period of 1893-1927. Octolasium lacteum (Orley) was also of frequent occurrence throughout the same period, though not listed by Garman. H. longicinctus Smith and Gittins (1915) was found in limited numbers in a woodland of the vicinity of Urbana in 1901 and in consid- erable numbers in parkings and lawns of the city itself in 1910-1915, but has not been noticed since the latter date. The most interesting feature -in the relations of the earthworms of the upland-soil localities that re- ceived attention, centered in the relations between Diplocardia communis Garman (1888) and Lumbricus terrestris Linnaeus, Muller. Garman’s description of the former species was based on material from the Cham- paign-Urbana region, and he states: ‘Hundreds were seen this spring in this locality, migrating during showers of rain.” The same statement has been equally applicable to this species during the period 1893-1927, with the exceptions noted in certain following statements. The actual time of the first arrival of Liwmbricus terrestris in Illinois is very uncertain. Garman (1888) and Michaelsen (1900) in their lists of North American OLrcocHAETA refer to Eisen’s (1874) record of its occurrence in “New England” but have no record farther west. The Mount Lebanon, New England, of Eisen’s record was actually in the eastern part of New York. The first definite record for Illinois is that of the writer published in 1900 and based on specimens found still earlier. The exact date is not known, but it was certainly before 1898 and prob- ably about 1896 that a few specimens were seen by the writer in a re- stricted locality in Champaign, crawling about during a rain storm. About the same date a workman engaged in digging a trench in an artificially forested area on the University campus (locally known as the Arboretum) found and gave to the writer a few specimens. These were the basis for the record mentioned above. During this period and for several years subsequently, it was necessary to send to dealers elsewhere for specimens needed for class work. Then came a time, not far from 1905, when specimens were sufficiently abundant in the Arboretum to meet some of the needs for material, but they had not spread in any appreciable num- EARTHWORM FAUNA OF ILLINOIS 349 bers to other areas. Subsequently, the area within a few blocks of the campus became abundantly stocked with them, while specimens of Diplo- cardia communis became correspondingly infrequent. In the forenoon of March 19, 1927, following a rainy night, the writer traveled along the streets bordering an area of about one-half mile square adjacent to the east side of the campus in Urbana and found Lumbricus terrestris abundant in the streets bordering all of the 24 city blocks involved, while the total number of specimens of Diplocardia com- munis seen was but 19, or an average of less than one per block—a marked contrast to conditions existing in the same region in earlier times when D. commumis was abundant throughout and L. terrestris was rarely seen. A trip on the following day through the area lying still farther east re- sulted in finding that D. communis was still abundant in a good deal of the territory covered and that L. terrestris was abundant in only a few detached areas. No noticeable difference was found in the relative num- bers of smaller introduced European forms, such as Octolasium lacteum, Helodrilus roseus and H. caliginosus trapezoides, which were still abund- ant in both of the localities examined. The area in Champaign into which L. terrestris has extended its distribution has also greatly increased in recent years. WOODLAND SPECIES No observations have been made which would provide information concerning changes in relative abundance of the species that are more commonly represented in decaying tree trunks, under logs, and in masses of decaying leaves. Helodrilus gieseleri hempeli Smith (1915), H. zeteki Smith and Gittins (1915), and H. tenwis (Eisen) (1874) are such forms, and the writer is unaware of any notable changes having taken place during the past 30 years in their relative numbers, or of the appearance in such locations in recent years of introduced forms not previously found there. STREAM-BANK SPECIES The stream which has been most easily accessible and from which mest of the collections of stream-bank species have been obtained, is locally known as the Boneyard Branch of Salt Fork. It is a small stream, but a few yards wide, which originates a short distance north of Cham- paign and flows south through the northern part of that city and then east through the eastern part and through the city of Urbana, which lies adjacent, and then joins the Salt Fork in the outskirts of the latter city. Its course extends across the University campus in the western part of Urbana. During the period 1893-1927 there have been extensive changes in the character of the water content and hence in the fauna contained. Increasing sewage contamination, due to increasing population and inade- quate sewage disposal equipment in the two cities, of which it furnished the principal drainage outlet, gradually led to the elimination of all of its fauna except that which could exist under conditions similar to those of an open sewer. The earthworm fauna of the banks has necessarily been 350 ILtinois NaturaLt History Survey BULLETIN influenced by these changes. Such conditions reached a maximum at about the time (1922-1923) that J. L, Hyatt, a graduate assistant, made an extensive series of collections of the earthworms inhabiting the soil in the banks of the stream in various parts of its course. Since that time the installation of a more adequate sewerage system and of a modern and efficient sewage-disposal plant has greatly altered the conditions, and resulting changes in the fauna are already in progress. During the time of Mr. Hyatt’s collecting activities there was great diversity in the degree of sewage contamination in different parts of the course of the stream. In the part lying north of Champaign and in the northern outskirts there was but little. In progressing down stream an observer would find con- tamination from the few factories, the streets, and other sources becom- ing more and more evident, and the waters were already laden with foul material before the eastern jiimits of Champaign were reached. Still further additions were made in its course through the University campus and Urbana. A study of the earthworms collected from the banks of the stream in various locations showed correlated changes in the relative abundance of the representatives of the different species of earthworms. Certain indigenous species and most of the species common in the upland-soil regions were found in much greater numbers in the places of least con- tamination, and certain other introduced species reached their maximum abundance where contamination was very pronounced. Most of the com- mon upland species were represented in at least small numbers, and in addition about a half-dozen other species were represented which have not been found in the upland-soil locations. A very decided lack of uni- formity was found in collections made from different localities even when the conditions and degrees of contamination seemed similar. Some species had a rather limited area of distribution, indicating a relatively recent introduction into the region. The specimens collected were obtained by digging them from the soil of the banks of the stream, and they were then taken to the laboratory and fixed in a well-extended condition. The specimens were all pre- served for the sake of greater certainty in identification and also with a view to their use in other ways, including a search for abnormal speci- mens, of which a considerable number were found. Collections were made from 11 different locations, distributed along some four miles uf the course of the stream, from the northern outskirts of Champaign to its junction with Salt Fork east of Urbana. Five of these locations were in Champaign and six in Urbana. For convenience they will be designated by the letters A to K, which will be applied to the locations in the order of their occurrence along the stream, beginning with the one nearest the source in the northern Champaign region. The number of collections in each location varied from one at A to twelve at F, but in most of them three or more collections were made from each, and the times of making the collections were distributed over parts of two years, 1922 and 1923. Unfortunately, no similar extensive series of collections had been made EARTHWORM FAUNA OF ILLINOIS 351 in earlier years; hence, definite comparisons of the fauna with that of earlier years could not be made, with the exception of locations F and G, where collections had been made at various times in preceding years. One surprising result of a study of the collections by Mr. Hyatt was the discovery of the presence of a considerable number of specimens of Helodrilus venetus hortensis, a European species which had been pre- viously recorded from North America only from California (Michaelsen, 1900). Thirty-one specimens were collected at one spot in location F on April 15, 1922, and a few had been found in neighboring locations in the preceding month. Still larger numbers were collected at location G in 1923. Since Mr. Hyatt had made collections at these two localities in 1921, and the writer also at various times in preceding years had made collections in the same places without finding any representatives of this species, it seems reasonable to assume that a recent introduction into this region has occurred. Another unexpected result was the finding of large numbers of the species H. chloroticus. A single specimen had been found by Mr. Hyatt in October, 1921, which was the first record from the Boneyard Branch. It probably was taken at location F or G, where only eight specimens were found in the 16 collections made in 1922 and 1923. I know of no record of careful collections prior to 1921 from the banks of the stream at loca- tion H and below, where Mr. Hyatt found several hundred specimens of H. chloroticus; hence, the supposition of a relatively recent introduction of this species has less supporting evidence. The only record of the species being found in Illinois prior to 1921, w hich is known to the writer is that of a dead specimen found September 12, 1918, by F. C. Baker while hunting mollusks in a shallow place in the Salt Folk about nine mules east of “Urbana, The waters of the stream where the specimen was found were carrying much sewage contamination received from the Bone- yard Branch at Urbana. An examination by the writer of the shores at a few points up stream from the place where the specimen was found, failed to disclose the presence of other specimens. Another species of which specimens were found to be most abundant in badly contaminated localities is H. subrubicundus (Eisen). It has been abundantly represented since 1911 but was not found during the first few years of the period beginning with 1893. The accompanying table shows the numbers and distribution of the specimens of the Hyatt collections and requires but little explanation. Locations 4, B, and C were those which were most free from sewage contamination. The first vertical column of figures gives the total num- ber of collections made at each of the locations, the next one shows the total number of specimens from each location, and the following columns show the total numbers of specimens of each of the species as found at each of the stations. The lower part of the table contains footings show- ing the total numbers of specimens of each of the species represented. 352 ILtinois NaTurAL History Survey BULLETIN In addition to these collections which were all from the banks of one stream, other collections were made in rivulets or ditches tributary to the stream, or in adjacent fields. The more pertinent features of a few of these will be mentioned. In a field near location A a collection of 80 specimens included 77 Helodrilus roseus, one Octolasium lacteum and two Diplocardia communis. A collection of 367 specimens from near the margins of a ditch near location C contained 350 D. singularis (Ude), the others being common upland species. A collection of 209 specimens from a small tributary stream near location D had 18 Helodrilus tetraedrus (Savigny), two of the variety H. t. hercynius (Michaelsen), three of H. tenuis, and the others were common upland species. A col- lection of 21 specimens from the margin of Salt Fork above the entrance of Boneyard Branch, and where there was no sewage contamination, had 11 Sparganophilus cisent Smith (1895), 8 Helodrilus tetraedrus, and two Hf. caliginosus trapezoides. Sparganophilus eiseni is widely distributed in the North Central States east of the Mississippi River and is abundant in the mud of the bottom and margins of many of their rivers and lakes, but does not appear to thrive in waters badly contaminated by sewage. TABLE I DISTRIBUTION OF BONEYARD BRANCH SPECIES OF EARTHWORMS 5 Ke ~ Naps S = s a 2S |S S| Seal asanae S-S | Soll Soe aes 2) 8.) sabe | SS 818 | So) Ss S| 2] sal8 | 2/3) 8)/2 183 | so) soo a) 8)e |e |) |e |e le 1) Sees A (1) 58 1 43 14 B (6) 83 666 22 45 63 6 28 C (3) 216 52 56 14 1 2 91 D (3) 246 8 2 11 a 104 3 36 5 E (2) 161 3 9 84. 29 8 een 782 106 54 79 11 7 448 5 48 ail 23 G (4) 917 4 4 204 36 4 402 3 248 2 10 H (2) 61 5 ib 6 10 32 a I (7) 1276 17 6 6 ily 1 235 475 500 2 15 2 Ay (3) 388 41 3 26 4 106 80 112 2 1 K ((83)) 219 65 13 30 18 50 20 23 Totals 5154 965 114 332 212 122 1572 618 1023 34 66 2 94 ~ a ee ee a EARTHWORM FAUNA OF ILLINOIS vs Oo oo ADDITIONS TO THE LIST OF ILLINOIS EARTHWORMS Helodrilus beddardi was not reported in the writer’s list of Ilinois species in 1915, but in a later paper (1917) dealing with the distribution of North American Lumpricipag, Illinois was included among the “new localities” in the account of that species. The specimens on which the record was based had been collected in October, 1910, by Dr. P. S. Welch, then a graduate student, who found them in a field north of Urbana. They were not carefully studied until 1916. Several specimens have more recently been collected near Muncie, 20 miles east of Urbana. In both of these localities the specimens were found in damp places near standing water in pastures. The finding of H. venetus hortensis and H. chloroticus in Illinois was mentioned in a paper by the writer (1924) dealing with the calciferous glands of LumsBricipar. Dr. Libbie Hyman of the University of Chicago collected specimens of H. chloroticus at Fox River Grove, Illinois, May 8, 1926. Helodrilus octaedrus has recently been found in two different Illinois localities. In November, 1925, S. L. Neave, a chemist of the State Water Survey, found several specimens in a very restricted area near the new sewage-disposal plant in the outskirts of Urbana; and in November, 1926, J. F. Muller, a research assistant, found specimens at Starved Rock, IIli- nois, in moss in crevices of the rock and crawling about on stems of vegetation. Lumbricus rubellus was represented in a collection at LaSalle, Illinois, in the autunin of 1925, made by Dr. R. E. Greenfield of the De- partment of Chemistry at that time, who found them under debris on the banks of the Illinois River. One specimen of a new form, together with specimens of other species, was collected by H. V. Heimburger, April 16, 1914, from the banks of a small stream flowing into the Sangamon River a few miles below White Heath, Illinois. The writer had sagittal sections made from one half of the anterior 17 somites, which showed that the specimen in some important characters resembles H. palustris Moore (1895). The specimen and sections were turned over to Mr. Heimburger, then a grad- uates student at the University of Illinois, and were part of the material used by him in the preparation of a thesis as a part of the requirements for a degree (A. M.). After an interval of several years the sections have been returned to the writer for examination and use in the descrip- tion of the species, but the unsectioned part has not been available for study. Helodrilus heimburgeri n. sp. Length, 7.7 cm. Diameter, 0.25-0.3 cm. Color, very little pigmenta- tion. Somites, 112. Setae, closely paired. Prostomium, epilobic. Clitellum, 25-32 and encroaching slightly on 33. First dorsal pore on 5/6. Male pores, paired on posterior part of 15, between seta lines b and c; surrounded by prominent glandular elevations. Oviducal pores, on 14 slightly dorsad of Db. Septa 11/12, 12/13, and 13/14 somewhat and progressively thickened, the latter about two or three times as thick as septa anterior to 11. The calciferous gland has inconspicuous lateral 354 ILtinoris NAtuRAL History SURVEY BULLETIN pouches in 10; has no conspicuous enlargements in 11 and 12; longi- tudinal chambers not much over 40 in number. Hearts, paired in 7-11. Spermaries, paired in 10 and 11. A pair of large chambers or atria in posterior part of 15, with large gland masses extending into 15 and 16, the latter one being smaller; sperm ducts extend dorsad on the anterior walls of atrial chambers and open into them at their summits. Sperm sacs, two pairs, in 11 and 12. Ovaries, paired in 13. Spermathecae lack- ing. Ovisacs, paired in 14 and open into the cavity of somite 13. One specimen, collected near White Heath, Illinois, by H. V. Heim- burger. Holotype.—Sections of a part of the specimen in the collection of the writer. But little attention was given by the writer to the external characters of the specimen when it was available, but a memorandum was made of the location of the clitellum. For certain other features the data of Mr. Heimburger have been utilized. The seemingly close relationship to the species described in 1895 by Dr. H. F. Moore under the genus name Bimastos, which species until the present time has been unique among the LuMBRICcIDAE in the characters of the distal parts of the sperm ducts, has added to the interest felt in making a study of the new form. A com- parative study has been facilitated by the use of three series of sections of H. palustris made from specimens kindly sent to the writer by Dr. Moore several years ago. EXTERNAL CHARACTERS Rather small in size and also similar to H. palustris in having a moderate number of somites, closely paired setae, and conspicuous gland- ular enlargements on 15, surrounding the external orifices of the spermi- ducal apparatus. The specimen was seemingly not in a state of sexual activity at the time of fixation, but apparently had passed through such a state previously and the gonads were of diminished size. The location of the clitellum on 25-32 very definitely distinguishes the new species from H. palustris in which the clitellum is on 23-28. The clitellum was stated by Mr. Heimburger to be nearly complete and to include the ventral setae. He also stated that no trace of tubercula pubertatis was found. The two species show marked similarity in the locations of the first dorsal pores; the external openings of the spermiducal organs on the posterior part of 15 and a little dorsad of seta line b; the oviducal pores on 14 slightly dorsad and posteriad of b; and of the nephridiopores, in the anterior part of the somites with some of them opening a little dorsad of seta line b, and others approximately midway between seta line d and the mid-dorsal line. Moore‘in his description of the nephridia of H palustris states: “The external opening is near the ventral couple of setae.” An examination of the sections from three of his specimens re- veals a variability in the positions of the openings similar to that of the new species. Like variability has been noted by certain other writers and myself in the location of these pores in other species of LUMBRICIDAE. (Langdon, 1895, p. 215) (Smith, 1915 and 1925) EARTHWORM FAUNA OF ILLINOIS 355 INTERNAL CHARACTERS The septa connecting the alimentary tract with the body wall are mostly without much thickening. Septa 11/12, 12/13, and 13/14 are somewhat thickened with the thickness gradually increasing from anterior to posterior; 13/14 being most thickened, but not very strongly. H. palustris differs in having none of the septa with increased thickness. The deeply staining glandular bodies attached to the wall of the pharynx and anterior esophagus in somites 4-6 in H. palustris are represented in only 4 and 5 in the new species; the space in 6 being largely filled by a mass of cells of different type and but lightly stained. The calciferous gland is similar to that of H. palustris (Smith, 1924) with approximately uniform diameter in 10-12, with paired esophageal pouches in 10, and but few more than 40 longitudinal chambers posterior to 10. Communi- cations of the chambers of the gland with the pouches in 10 were found in both species and none were found elsewhere. No especial differences have been noticed between the two species in the location and relations of the crop and gizzard, respectively, the former in 15 and 16 and the latter in 17 and 18. Circulatory system —This has not been studied in detail otherwise than to determine the relations of the hearts and lateral-longitudinal vessels to the other vessels of the vascular system and to the calciferous gland. Five pairs of hearts are present in 7-11 and have the usual rela- tions to the dorsal and ventral vessels. The hearts of 11 are similar in size to the others. An examination of the three series of sections of 7. palustris resulted in finding similar conditions in them except that in two of them the hearts of 11 were much smaller than the others. In no in- stance was there any indication of any of the hearts passing into the wall of the alimentary tract in a part of their course, as described by Moore (1895, p. 489) in some of the specimens examined by him. The lateral- longitudinal vessel of one side of the specimen of the new species, which was included in the sections studied, extends through the space between the anterior pairs of hearts and the esophageal wall to the posterior part of 9, and then dorsad and mesad along the anterior surface of septum 9/10 until near the dorsal side of the esophagus where with a turn poster- iad it extends through the septum and presumably joins the dorsal vessel about midway of the length of somite 10. Since the sections do not include much of the dorsal vessel and the last ones are imperfect, a more positive statement cannot be made. In his description of H. palustris, Moore states: “A pair of esophageal vessels arise from the sub-intestinal trunk in somite X and pass laterally forward to supply the tissues sur- rounding the anterior portion of the alimentary canal.” Elsewhere on the same page he says, “The vascular system has not been investigated, except in a very general way.” The writer has not found among the Lumpricipar studied by him any species in which the lateral-longitudinal vessels arise from the ventral vessel, and but few in which they do not have their posterior union with the dorsal vessel in 12. The three series of sections of H. palustris available for comparison include a transverse, 356 ILLInois NATURAL History SuRVEY BULLETIN a sagittal, and a frontal series. All of them have been utilized but have not always been equally helpful for each particular problem. In all three specimens the course of the lateral-longitudinal vessels has been similar to that found in the new species. They extend to the posterior part of 9, then dorsad and mesad anterior to septum 9/10, then through the septum into 10, where they join the dorsal vessel. The junction with the dorsal vessel is clearly shown in two of the series and nearly as certainly in the third one. Reproductive organs—There is marked similarity between the two species in respect to the reproductive organs. There is agreement in the number and location of the gonads in 10, 11, and 13, and of the sperm sacs in 11 and 12. Spermathecae are lacking in both. No essential differ- ences have been noted in the characteristics of the oviducal organs. The characteristics of the spermiducal organs are of especial importance in determining the relationship of this species to others, and it would be highly desirable to have specimens more nearly at the height of sexual activity than is the only one of the new species now available. In this specimen the maximum height of the atrial chamber including the thick glandular wall, as seen in sagittal sections, is but little more than half of the dorso-ventral diameter of the worm. The apex of the atrial cavity, which is the place where the slender cylindrical lumen of the sperm duct opens into that cavity, is about one-third of the diameter of the worm from the ventral margin, as seen in section. In the specimens of H. palustris the chamber and cavity are more nearly cylindrical and extend nearly to the dorsal wall of the body cavity. In the new species, as in the other, the course of the sperm duct after reaching somite 15 is dorsad along the anterior wall of the chamber, going deeper and deeper into the glandular wall tissue, until finally reaching the uppermost part of the chamber, or atrial cavity, where the lumen of the duct is continuous with the cavity. No modified setae with related glands in 13 and 16 comparable with those of H. palustris have been found in the new form, but perhaps such setae may be present at the time of sexual activity. Large masses of gland cells associated with the wall of the atrial chamber and extending into the body cavities of 15 and 16 are present in the new species and resemble those ot H. palustris in general appearance, but no careful study of their histological characters has been made. Nothing is known concerning the presence or absence of spermatophores in the new species at the time of sexual activity. Moore created the genus Bimastos for the species palustris, in part because of the striking difference from other LUMBRICIDAE in the char- acter of the terminal organs of the spermiducal apparatus, to which he ap- plied the terms prostates and atrial chambers. Later writers have used the name with corrected spelling (Bimastus) as a name for a sub-genus to in- clude Moore’s species and others that resemble it in having no spermathe- cae and regardless of the presence or absence of atrial chambers. To the writer, the existence of this latter character in two species that are also closely related in other ways seems to be a sufficient basis for the restric- EARTHWORM FAUNA OF ILLINOIS 357 tion of the use of the name Bimastus to these two species and others that may later be discovered having similar characteristics including the paired atrial chambers. There may perhaps be as much justification for recog- nizing a genus Bimastus as there is for the genus Octolasium. If more were known about the details of the relations of the lateral-longitudinal blood vessels in the various species of LUMBRICIDAE, it might aid in the determination of a more correct classification. The similarity between H, palustris and the new species in the course of the lateral-longitudinal vessels seems to be a matter of considerable significance. The only other species in which the writer has found a similar course in these vessels is H, octaedrus (Savigny), but in this species there are several important characters in which it differs materially from the Bimastus group. The lateral-longitudinal vessels of the three last-named species seem noticeably smaller and less conspicuous than those of other species in which these vessels join the dorsal vessel in 12. DISTINGUISHING CHARACTERS OF ILLINOIS SPECIES A list of species, together with statements of the important characters which serve as the basis for determining their systematic relationships, can be presented in a convenient and compact manner in tabular form (Table IL), as was done in an earlier paper on the species of the State (Smith, 1915). Before presenting this list, reasons will be given for changes in the statements of some of the characters of certain species from those given in the former list or from those commonly found in the literature dealing with such species. In the former paper the sperm sacs of H. tetraedrus and of its variety hercynius were listed as being contained in somites 9-12, in conformity with statements commonly made by writers on the group. Since the majority of the specimens examined by the writer lack sperm sacs in 10, though small ones are present in that somite in occasional specimens, they are listed as in 9, 11, 12. A change has also been made in the location given for the spermathecal pores of the same forms. Instead of 8/9 and 9/10 as stated by earlier writers and in the former paper, the location of these pores in most specimens has been found by the writer to be in 9/10 and 10/11, and this location has also been found by Cognetti (1905) to be the normal one in European specimens (Smith, 1917, p. 162). Specimens apparently related to H. tetraedrus, but having spermi- ducal pores on other somites than 13 or 15, have been found by investi- gators in Europe, and certain species, varieties, or forma have been named on the basis of such specimens. Tetragonurus pupa Eisen with spermi- ducal pores on 12 was described from specimens collected in North America near Niagara Falls, and one specimen considered by Eisen as the type and presented to the United States National Museum was later studied by the writer and found to be in all probability an abnormal representative of H. t. hercynius (Smith 1917, p. 163). 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In eight of these specimens asymmetry is found, and in ten specimens the spermiducal pores are paired on somites other than 13 or 15. Sections were made of parts of these ten specimens and studied with the following results. In one specimen with spermiducal pores on 14, the clitellum, tubercula pubertatis, oviducal pores, spermathecal pores, gonads, sperm sacs, hearts, and calciferous gland were all found one somite anterior to the location normal in the variety hercynius. In each of three specimens with spermiducal pores on 12, the various parts named above are located one somite anterior to the positions normal in H. tetraedrus typicus. In four specimens with the spermiducal pores on 11, the other organs named are two somites anterior to the positions normal for specimens of that species. In one specimen with spermiducal pores on 10, the various other organs named, in so far as they are present, are three somites anterior to the normal positions. Only the three posterior pairs of hearts were recognized. In this specimen there are four sper- mathecae in 4-7 on one side and three in 5-7 on the other side. The gen- eral appearance of a few anterior somites suggests strongly their having been regenerated. One specimen that at first glance with a lens showed spermiducal pores on 9 was found on more careful study to have lost some anterior somites (probably four) and had just begun regeneration for their replacement. Thus far the writer has not made a sufficiently care- ful study of the specimens with spermiducal pores on 11 or on 12 to pro- vide a basis for a satisfactory conclusion concerning the probable cause of such departures from the normal numerical relations—whether it may be due to injury and subsequent incomplete regeneration or to some other cause. H. venetus hortensis is given in the table as having a length of 4-10 em. instead of the 3.5-5 cm. found in an earlier paper (Smith, 1917) and based on the statements of European writers. Specimens in the collec- tions studied by the writer included several that were 7-10 cm. in length. They had been anesthetized before fixation and were in a well-extended condition. Specimens of H. octaecdrus from Norway, Colorado, and Illinois have been sectioned, and in them the writer has found hearts in 7-9 only. In specimens from Virginia no hearts have been found posterior to 10. In the other species of Lumsricrpak listed the posterior pair of hearts is in 11. Specimens of H. tenuis are usually without spermathecae, but the writer (1917, p. 177) has reported specimens from Michigan and Indiana with spermathecae imperfectly developed or in reduced numbers (less than four), and more recently has found three specimens from Homer Park, Illinois, which also have spermathecae in reduced numbers or im- perfectly developed. EARTHWORM FAUNA OF ILLINOIS 361 GENERIC NAMES OF LUMBRICIDAE There has been much confusion in the present century in the use of generic names for LumMBricrpAE. In 1845, Hoffmeister created a genus Helodrilus for a species oculalus which he erroneously believed to differ from related forms in the absence of a clitellum in all stages of the life history. The related species were left in the genus Lumbricus. In 1874, Eisen separated the species of Lumbricus into four groups, leaving but few species in Lumbricus and creating three new genera: Allurus, Dendrobaena, and Allolobophora. Michaelsen, in a monographic paper (1900a) on OricocHaeEta, replaced the name Allurus Eisen, which was preoccupied, by the new name Eiseniella Michaelsen. He also substi- tuted the genus name Helodrilus Hoffmeister for Allolobophora Eisen, using the latter name for a subgenus of Helodrilus. He felt that a strict adherence to certain rules of nomenclature, which he was obligated to follow, required such substitution. In this procedure he was followed by the majority of writers of systematic papers dealing with Lumsricmar. During the past few years there has been a rather general tendency among various writers, including Michaelsen, to restore the genus Allolobophora and discard Helodrilus. Five groups—Eiseniella, Eisenia, Dedrobaena, Bimastus, and Eophila—are variously treated as distinct genera, or as subgenera of Helodrilus or of Allolobophora, depending on which of the latter happens to be recognized as a valid genus. Such diversities of terminology cause little inconvenience to the specialist familiar with the situation, but are naturally confusing to others. In the present paper the writer has preferred to follow the precedent set in his earlier paper (1917) based on Michaelsen’s paper of 1910. The real need for a satisfactory system of nomenclature carefully followed is obvious. LITERATURE CITED The following list includes the papers to which direct references are made in the text. More extensive lists of the literature on OLIGOCHAETA will be found in the bibliographic lists in some of the papers here listed, especially in those of Beddard (1895), Michaelsen (1900a and 1910), and of Smith (1917 and 1924). Bepparp, F. E. 1895. A Monograph of the Order of Oligochaeta. Oxford. COGNE?TI DE Martits, L. 1905. Lombrichi liguri del Museo civico di Genova. Ann. Mus. civ. Stor. nat. Genova, (3) 2:102-127. EISEN, G. 1874. Bidrag till Kannedomen om New Englands och Canadas Lumbri- cider. Ofv. Vet. Akad. Férh., 31:41-49. GARMAN, H. 1888. On the Anatomy and Histology of a New Earthworm (Diplocardia communis, gen. et sp. nov.). Bull. Ill. State Lab. Nat. Hist., 3:47-77. HeEIMBURGER, H. V. 1915. Notes on Indiana Earthworms. Proc. Ind. Acad. Sci., 1914. 362 Intinois NATuRAL History SURVEY BULLETIN LANGDON, Fanny E. 1895. The Sense Organs of Lumbricus agricola Hoffm. Jour. Morph., 11:193-234. MICHAELSEN, W. 1900. Die Lumbriciden-Fauna Nordamerikas. Abh. nat. Ver. Hamburg, 16:1-22. 1900a. Oligochaeta. Das Tierreich, 10 Lief. xxix-575 pp. Berlin. 1910. Zur Kenntnis der Lumbriciden und ihrer Verbreitung. Ann. Mus. Zool. Acad. Imp. Sci. St. Petersburg, 15:1-74. Moors, H. F. 1895. On the Structure of Bimastos palustris, a New Oligochaete. Jour. Morph., 10:473-496. Smiru, F. 1895. A Preliminary Account of two New Oligochaeta from Illinois. Bull. Ill. State Lab. Nat. Hist., 4:138-148. 1900. Notes on Species of North American Oligochaeta.. | Ii.) Lastof Species found in Illinois, and Descriptions of Illinois Tubificidae. Bull. Ill. State Lab. Nat. Hist., 5:441-458. 1915. Two New Varieties of Earthworms with a Key to described Species in Illinois. Bull. [1l. State Lab. Nat. Hist., 10:551-559. 1917. North American earthworms of the family Lumbricidae in the col- lections of the United States National Museum. Proc. U. S. Nat. Mus., 52:157-182. 1924.. The calciferous glands of Lumbricidae and Diplocardia. Jil. Biol. Monographs, 9:1-76. 1925. Certain Differences between Text-book Earthworms and Real Earth- worms. Trans. Ill. State Acad. Sci., 17:78-83. SmirH, F.., AND GITTINS, E. M. 1915. Two New Species of Lumbricidae from Illinois. Bull. Ill. State Lab. Nat. Hist., 10:545-550. ey Al STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVIL _ BULLETIN Article XI. The Hessian Fly and the Illinois Wheat Crop BY W. P. FLINT and W. H. LARRIMER PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS August, 1928 , adtale 23. ee LIVIRGSTON daca ree i | yROQUOIS GREENE | ~ Macon ean Fest: JERSEY | | | } seit > + paSETTEK | er aces | JARPER (ere . x5 BON ol eS CT acer aS a | ae x penta ee MARION MART er Lone ry mh CLINTSN | k | ST CLaIR | . = | wasmineTon | 2 a) WAYNE - j 3 y Map of Illinois showing average date of seeding wheat for highest yield and to avoid damage by Hessian-fly. (65260—1M—10-31) <7 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVII. BULLETIN Article XI. The Hessian Fly and the Illinois Wheat Crop BY W. P. FLINT and W. H. LARRIMER PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS August, 1928 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. Sue ton, Director BOARD OF NATURAL RESOURCES AND CONSERVATION A. M. SHELTON, Chairman WILLIAM TRELEASE, Biology JoHN W. Atvorp, Engineering Henry C. Cow es, Forestry Cuartes M. Tuompson, Representing Epson S. Bastin, Geology the President of the University of WitiiAMmM A. Noyes, Chemistry Illinois THE NATURAL HISTORY SURVEY DIVISION STEPHEN A. ForsBeEs, Chief ScuHNeEpP & BARNES, PRINTERS SPRINGFIELD, ILL. 1928 1905—3M VotuMEe XVII ARTICLE XI THE HESSIAN FLY AND THE ILLINOIS WHEAT GROP W. P. Flint’ and W. H. Larrimer? INTRODUCTION The Hessian Fly, an insect that infests practically all of the large wheat-growing areas of the world, was first found in North America on Long Island in 1779 and was probably brought into this country in the straw used by the Hessian Troops sent here during the Revolutionary War. It was first recorded in Illinois in 1544, according to Webster®, and it has been a factor in wheat production in this State ever since that time. Of all the agricultural crops grown in Illinois, wheat is second in importance, being outranked only by corn. The annual value of the wheat crop to Illinois farmers is in the neighborhood of fifty million dollars. Of the 41,034,000 bushels produced in 1926, almost 95 per cent, or 38,934,000 bushels, was winter wheat*. Success in growing winter wheat in this State depends on many factors, including the w eather, type and fertility of soil, variety of w heat grown, presence of plant diseases, and infestation by insects, particularly the Hessian Fly. In years when this insect is very abundant, it may be the most im- portant factor in the production of winter wheat, for it sometimes de- stroys a fourth or even a half of the entire crop of the State. On indi- vidual farms it may, and often does, destroy from fifty to one hundred per cent of all the wheat plants in a field. The Hessian Fly feeds on rye and barley, besides wheat, and it has been found on some wild grasses, though not in sufficient numbers to affect the surrounding wheat. It does not feed on oats. For many years, experiments have been carried on by entomologists and others in an effort to devise practicable methods of protecting the wheat crop against the ravages of this pest. In order to fight the fly successfully, we had to learn just how it lives through the year, and just where it is to be found during each season. A vast amount of detailed information on these questions has been accumulated as a basis for prac- tical recommendations, but a brief outline of the main facts in the life history of the insect will serve our present purpose and show why certain methods are here recommended. 1Chief Entomologist, Illinois State Natural History Survey. 2 Senior Entomologist in charge of cereal and forage insect investigations, United States Department of Agriculture, Bureau of Entomology. 8 Webster, F. M. The Hessian Fly. Ohio Agr. Exp. Sta. Bull. 108. (1899.) 4Surratt, A. J. Illinois Crop and Live Stock Statistics. Dept. of Agr. Cire. 360. (1927.) [363] 364 IntmNoris NATuRAL History SuRVEY BULLETIN LIFE HISTORY The Hessian Fly passes the winter in the puparium, or “flaxseed” stage, resting as a larva, or maggot, within a brown flaxseed-like case, which is usually to be found behind the lower leaf sheath of early-sown or volunteer wheat, and sometimes in the old stubble. In the latitude of central Illinois the spring brood emerges about the middle of April; that is, the maggots within the flaxseed cases change to the pupal stage and shortly thereafter burst open these cases and emerge as small sooty-black flies, a little smaller than the common house mosquito. The adult flies do not feed, so far as is known. The females, whose abdomens are packed full of orange-red eggs, mate with the males shortly after emerging and then proceed to deposit their eggs on the leaves of the wheat. The eggs, which are so small that they can hardly be seen without the aid of a magnifying glass, are almost always deposited in the little grooves on the upper side of the wheat leaf. Hatching takes place from three to twelve days later, depending on the temperature and moisture. — Fig.1. Adult Hessian Fly, male. Fig. 2. Adult Hessian Fly, female. (U.S. D. A. Bureau of Entomology.) (U.S. D. A. Bureau of Entomology.) The little orange-red maggots which hatch from the eggs work their way downward until they reach a point where the leaf-sheath is joined to the main stem of the wheat plant. Their descent may be assisted by a drop of dew or rain. Having reached this point, they become permanently established and feed by sucking out the sap. A shoot that is attacked by several of them is weakened and finally killed. Under favorable weather conditions, the maggots grow very rapidly and become full-grown in about two weeks; and by this time they have attained a length of about an eighth of an inch and have become nearly white. Shortly after the maggot is full-grown, its outer skin loosens, be- comes detached from the inner skin, and then turns brown, forming a pro- tective case, which is known as the puparium or “flaxseed,” and from which the adult fly will emerge in due time. 365 Tue Hessian FLY AND THE WHEAT Crop (fbojowoqwwg fonvamg ya's’) Wweyo ALoxStY OFT] ATW UBISSeAH ‘g “BIW CRZISHOTS SIWOIIT ONY LNY RS LO ISVP SHIFTS ODD FHA ATMIN i Sa ] ~CPISKY EH SINOIIG LODO | WTbLS OL SIOD ONY SFT ANY Id AHLI FH 0. | LAM CFIPWED DMAGH | NO STH2¢H LODDPAW | SIAVI7 NO SIDI SAVT ATF ‘ ‘ y oY i ATTY FIWOWF AXLIOGE GIFEXA TS ONL NIAA ( | 7 QL OMIT DWAIN OFISKETS SNALNINA. OFISKY TS PITT Ol ONIN eee, ONY CFNTHESM ANTS ver i ) T | | | \ | | | \ ' i) | \ | | | | | 1 FIG | ALTA LLA STHIUbH LOOK ONE LEFHM PRIMM | 2NIOA NO SOQP SAY7 ATF ew AVS SIWOITS OFISKVTS y Gare | QPRIVINT AULFHO | | | | | | | | | | | t L092 0 AIT | t 366 ILttinois NATURAL History SURVEY BULLETIN In central Illinois the spring brood of maggots, which usually hatch in April, may reach the flaxseed stage by the first week in May; and some- times, if conditions are favorable, adults may come out from some of these flaxseeds during the early part of May and lay eggs which produce a sec- ond spring brood of maggots. These maggots usually become established rather high up on the wheat plants and cause serious breaking over of the wheat when the heads begin to fill. The Hessian Fly has been associated with wheat so long that it passes from stage to stage in its life history according to the development of the wheat plant. As the wheat ripens and the straw hardens and dries, the maggots change into the flaxseed stage, in which they remain, inactive, in the stubble or in the cut straw in the stack. If there is little rainfall during the summer, so that conditions are unfavorable for the growth of volunteer wheat, the flies remain in the flaxseed stage until the time of heavier rainfall in early autumn; but if the summer’s rainfall is suf- ficient to bring about a growth of volunteer wheat, the flies emerge and lay their eggs on the wheat at about the time the volunteer plants become two-bladed ; and the maggots hatching from these eggs become full-grown and ready to produce another brood of flies by early fall. In most years, fortunately, the flies remain in the wheat stubble until the early fall rains have produced good conditions for the growth of volun- teer wheat, or have brought up early-sown wheat in the fields. They usually begin coming out about the middle or latter part of August in central Illinois (somewhat earlier in northern Illinois and later in southern Illinois) and continue to emerge for about six weeks. These adult flies cannot survive the winter, and in central Illinois practically all of tliem die by the first week in October. If they find no growing wheat or other host plants on which to lay their eggs, they leave no progeny ; but if they do find growing wheat, a fall brood of maggots will be produced, which will become full-grown and reach the flaxseed stage before cold weather sets in, and will thus be able to withstand the lowest winter temperatures that are likely to occur in any part of Illinois. From these statements, it will be seen that normally there is at least one spring brood and one fall brood of the Hessian Fly. Under more fa- vorable conditions there may be two spring broods and two fall broods, and under the most favorable conditions, two spring broods, one summer brood, and two fall broods, or five broods in the course of a single year. Some live puparia of the first spring brood always carry over to the fall, and usually even through the winter to the second season, thus providing for perpetuation of the species under adverse conditions. The development of this insect is very largely dependent on tempera- ture and moisture, or rather a combination of the two, as high tempera- tures will not bring through a brood of flies unless combined with an abundance of moisture. Some idea of the great differences in the length of time required for the completion of the life cycle under different sets of weather conditions may be gained from the fact that McColloch® in Kansas carried a brood through one complete generation in a period of 5 McColloch, James W. Variations in the Length of the Flaxseed Stage of the Hessian Fly. J. Ee. Ent. 12: 252-255. (1919.) a ee ee ee THE HessIAN FLy AND THE WHEAT CROP 367 twenty days, while under other conditions it required four years for an individual to complete the same cycle. Under normal weather conditions in Illinois, the relatively fly-free date is September 18 for the northernmost tier of counties and pro- gressively later as one goes southward, as shown on the map in Figure 4. ISTEPHENSON | W/NNEBAGO | BOONE} Sept i ee ei a Brie Wrak WHITES/DE area a KENDALL VERMILION ee DOUGLAS EDGAR arn e pee FFG Lae JASPER (cag : oe ea WAYNE Cs me Aga WW HAMILTO! PERRY 7 oe a r? WAS ms /ROQUO!S fOWAROS Fig.4. Map of Illinois showing normal relatively fly-free dates for wheat seeding. 368 ILtinois NaturAL History Survey BULLETIN CONTROL MEASURES It is advisable for wheat growers to protect their crop against the Hessian Fly in every way possible. The methods that have proved to be the best may be summarized as follows: First: Sow wheat late enough, so that it will come up and make a growth at a time when there are no adults of the Hessian Fly to deposit their eggs upon it, but early enough to withstand the winter. Second: Keep down all volunteer wheat, in so far as possible. Third: Have the seed bed in good condition and the land in a high state of fertility, so that the wheat plants will start a vigorous growth. This is especially important in years of moderate to light infestation, when the first shoots to come up may become infested and die, but the later ones may still make a good crop. Fourth: Plow under during the summer the stubble from the last crop, if such plowing does not interfere with good agronomic practice. This is an important, though often neglected, means of fighting the fly. Fifth: Grow strong-stemmed varieties of wheat which do not easily break over. Of these methods, the proper date of seeding is the most important. It has long been recognized, throughout the wheat-growing areas of North America, that wheat sown early in years when the Hessian Fly is abundant will be killed, and that wheat sown moderately late will often entirely escape infestation. On the other hand, there is a danger that very late seeding will cause a reduction in yield through winter killing. DATE-OF-SEEDING EXPERIMENTS In order to determine as exactly as possible what effect the date of seeding has on the degree of infestation by the Hessian Fly and on the yield of wheat, the entomologists of the Natural History Survey have been conducting a series of experiments since 1917 in fields in six different parts of the State, namely, in Winnebago (Boone, two years), LaSalle (Bureau, three years), Hancock, Macoupin, Jackson, and Champaign counties. During this time the federal Bureau of Entomology, cooperating with the Natural History Survey and the Illinois Agricultural Experiment Station, has also made similar experiments in Marion, Pulaski, and Ran- dolph counties. The general plan of these experiments was to sow a series of plots of wheat, each at least a half-acre in extent, making the first seeding at least two weeks before the date which was considered the average rela- tively fly-free date for that particular locality, and making the next seed- ing approximately five days later, and so on, until six or more seedings had been made. This plan gave a range of seedings extending over a period of one month or more, including approximately two weeks before and after the normal fly-free date. ee THE HESSIAN FLY AND THE WHEAT CROP 369 In all fields north of Macoupin County, the variety of wheat grown was Turkey Red, most frequently the strain Turkey 10-110 developed by the University of Illinois. Fultz and Fulcaster were the varieties gen- erally grown in the southern fields. With the exceptions of the plots on the University Farm at Urbana and the field in charge of the Bureau of Entomology at Centralia, the seed- ings were made by farmers in parts of their wheat fields. Some of the experiments have been transferred from one farm to another in the same locality. During the first half of November in each year, the percentage of fly infestation in each plot was taken by the entomologists, using the sam- pling method described in a previous paper®. The yield of wheat from each plot was measured at the regular time of harvest. ISSUE ANS The following tables give the yield in bushels per acre and the per- centage of fly infestation for each field and each date of seeding in each year throughout the period of the experiments, and the accompanying graphs are made from the averages for the entire period. Several facts show up very clearly in these results. In the first place, it is evident that there is a very definite relationship between yield and in- festation. By consulting the tables it will be seen that, without any ex- ception, wheat heavily infested by the Hessian Fly has made lower yields than wheat grown during the same year and in the same field but seeded later so as to avoid the fly. Furthermore, as shown in the graphs, the average yield has always increased as the infestation decreased. Good yields were obtained from some early seedings during certain years, but never when the fly was abundant. In general, the degree of infestation has been of great importance in early seedings but of no consequence in late seedings. From the results of this work, and also from many other observations made in fields throughout the State, it is evident that the yield is not noticeably affected when less than ten per cent of the plants in a field are infested. WINNEBAGO AND BooNE COUNTIES In the extreme northern part of the State, the experimental plots have been located on farms in the vicinity of Rockford, for four years in Winnebago County and for two years just across the boundary line in Boone County. The work was begun in 1917 and continued to 1926 except for interruptions in 1918, 1921, and 1923. The dates of seeding ranged from September 2 to October 6. The painstaking work of Mr. E. R. Derivent, who has been our cooperator for several years, has contributed to the success of the experiment. 6Flint, W. P., Turner, C. F., and Davis, J. J. Methods in Entomological Field Experimentation. J. He. Ent. 12:178-183. (1919.) 370 ILLInoIs NATURAL History SURVEY BULLETIN Table I shows the yields from all the plots, arranged according to the date of seeding, for each of the six years; it also shows what per cent of the wheat plants in each plot were infested by the Hessian Fly. The normal relatively fly-free date for this locality is September 18. The aver- age yield from all plots seeded before this date has been 24.8 bushels per acre. From all plots seeded after this date, the average yield has been 28.1 bushels per acre. Judging from these results, anyone growing wheat in the northern tier of counties in the State will obtain the best yields if he sows during the period of September 17—30. It seems, also, that the degree of fly in- festation drops very sharply in seedings made after September 16 and, in fact, can be considered of no consequence in its effect on yields from such seedings. The direct relationship of fly infestation and wheat yield ap- pears very clearly in the graphs of Figure 5, which are made from aver- ages for the six years. TABLE I Per Cent INFESTATION BY THE HESSIAN FLY AND WHEAT YIELDS (BuUSHELS PER ACRE) WINNEBAGO AND BOONE COUNTIES 1917—1926 | | “ Sept. ase Sept. Sept. | Sept. Sept. Sept. Oct, Date of seedingamr 2-6 | 711 | 12-16 | 17-21 | 22-26 | Ce | 28 | | felts Infestation November, 1917............... 8 7 4 2 0 0 TIES Werellasucphcecocesacnenoose 33.8 27.2 34.30 5. 37.2 36.3 33.8 Infestation Ay November, 1919...............- 41 48 23 2 i 7 Fiohs Bach IBA MAGS Ss onéonasondsqososnd 17.3 18.5 19.3 & 20.1 19.3 metas ceria Infestation > November, 1920........./.---++ 21 1 1 2) 0 0 1921) WWieldicececesmem neue aoe 14.5 20.4 23,4 BS 2107 25.0 23.8 Infestation & November, 1922...............: ase 4600 60 a 15 0 0 1923% Wield se. seestnaesneos aeto care 1573) eee 13.7 16.1 16.1 a Infestation & November, 1924............--.. 12 0 2 65 0 0 0 1925 UYaeldt teas cecmaeniciice 27.2 23.6 ale 34.3 39.6 33.2 Infestation 5 November, 1925..........-00005 5 chats 500g 2 0 0 Natal We acononcecnbaeoouna%6 32.8 ee Apes 35.9 38.9 32.4 Average Infestation........... 17 14 18 4 6 0 0 EAVELA SE Ye) Cleats eee 25.0 22.4 26.5 28.7 28.5 29.4 24.4 a es THE HESSIAN FLY AND THE WHEAT CROP 371 DATE _oF SEEDIN' Septé-6| |Sep 207 p Sp INFESTATION PERCENT yi y a ternal ty free cate\s Sept /B ——————— ° Fig.5. Graphs showing average yield and average infesta- tion for experimental plots in Winnebago and Boone counties. LASALLE AND BUREAU COUNTIES The experiment which was started in Bureau County in 1917 has been continued in LaSalle County since 1920. The work has been done on three different farms. Mr. L. C. Rinker, of Grand Ridge, who has co- operated with the Natural History Survey for several years in this work, has been very careful in his handling of the fields. Most of the seedings were made between September 7 and October 6. DATE oF SEEDING [SeptZ226] [ept27an] [oct 2-6 00 x 40 x 80 = s wu 2 & ry x0 5 608 c k & gq g 3 6 S we. = of BS 8 g : : : v 0 o o Fig. 6. Graphs showing average yield and average infesta- tion for experimental plots in LaSalle and Bureau counties. 372 ILLinois NATURAL History SuRVEY BULLETIN As shown in Table II, wheat sown in the period of September 17—26 gave the highest average yield. Infestation by the Hessian Fly was fairly heavy in most years up to September 22, which is the normal relatively fly-free date for this locality. This date, in general, coincides with the date of highest yields. In years when the Hessian Fly has been very abundant, the early seedings have made poor yields. Figure 6 shows graphically how the average yield rises as the average infestation falls in plots sown during the first three weeks in September; it also shows a slight reduction in yield from plots sown in October, due to winter killing. Tarte I Per Cent INFESTATION BY THE HESSIAN FLY AND WHEAT YIELDS (BUSHELS PER ACRE) LASALLE AND BUREAU COUNTIES 1917—1926 Date oltseciincame- Sept. | Sept. | Sept. | Sept. Sept. Sept Oct. Seem cca 2-6 7-1 12-16 | 1721 2226 Octet 2-6 Infestation November, 1917: -..-...020.6< ener 47 27 0 wares 0 0 Ew stalslbeesasaurocsa inte eae 27.8 31.9 35.6 rida. 32.2 27.8 Infestation November, 1918............. ato 15 12 4 0 0 0 TL Bh aitAnncdactuecosacor Aetd 34.8 36.3 43.3 47.7 41.9 41.8 Infestation November, 1919............. 79 58 51 45 a 14 18 RPE NAGIGIER soScdokneratacscd 20.9 20.9 29.0 24.2 = 33.1 27.4 o Infestation aq November, 50 28 44 3 43 43 11 1921 Yield 27.8 29.8 32.3 = 33.1 26.6 27.4 n Infestation a November, 1921............. 74 50 37 agac sae 0 3 fs A922 Yael dire ese tit as cere 12.1 16.1 20.1 Sao £ 20.1 20.1 ' Infestation 5 November, 1922............. Rene 83 90 79 = 25 7 0 NPY a Cil aaAsaaeeanaaesoedce nei 16.9 25.0 29.8 ns 25.8 35.4 29.0 C=] Infestation Z November, 1923............. boat 53 29 0 6 0 0 0 1924 Wield rer eravineecis cucu eft HiBiOt 19.8 27.0 40.3 5 39.5 36.7 29.4 a Infestation November, 1924............. Aa06 33 33 23 16 6 2 UCP EP eG Roradacersacadronns ce 41.5 42.8 47.1 47.1 43.5 45.0 Infestation November, 1925............. Sele 19 20 0 0 0 0 1926) Vieldvy ain. ee sccmeoner sod 32.8 33.9 34.4 37.3 42.0 35.0 Average Infestation........ 17 45 36 24 12 8 2 Average Yield.............. 16.5 26.5 30.6 36.0 35.4 34.0 33.6 THE HESSIAN FLY AND THE WHEAT CROP 373 Hancock County The experiment in Hancock County was carried on for the entire period from 1917 to 1926 on the farm of Mr. Kent Campbell near La- Harpe. Mr. Campbell has taken a great deal of personal interest in this : work, and it is due to his care that we have such a complete set of records as are shown in Table III. His farm is kept in a very good state of fer- tility, and the average yield from his plots for the entire period is higher than that from any others in the State. The yields in the plots, more- over, correspond very well with the yields generally obtained in his fields. TABLE IIT Per Cent INFESTATION BY THE HESSIAN FLY AND WHEAT YIELDS (BUSHELS PER ACRE) HANCOCK COUNTY 1917—1926 | = | Date of Sept. Sept. Sept. Sept. oy : Oct. Oct. Oct. seeding 7-11 | 12-16 17—21 22—26 eel 26 | 7-11 | 12-16 | I Infestation November, 1917..... 42 AocS 3 0 0 wane 0 1919 Yield.......... 33.8 AaBS 42.8 50.0 49.7 =a 40.3 Infestation November, 1918..... 45 13 2 0 0 0 1919 Yield.......... 34.2 37.3 35.3 35.5 36.3 40.3 Infestation = November, 84 91 Se 33 g 0 0 1920 Yield 20.8 23.4 sane 31.0 = 35.4 34.6 Infestation = November, 1920..... 90 81 58 49 = 36 2 TLE a G PARR rae 21.8 29.0 26.6 25.0 = 27.4 29.9 Infestation = November, 1921..... Shes aces 9 2 2 O 0 1922 Yield.......... 3555 Rees 18.1 20.9 = 23.4 24.2 Infestation S November, 1922..... .... 22 21 7 = 2 2 1923) Wield: <..-....< 5ae5 39.5 44.3 $4 = 44.3 45.1 50.8 Infestation =) November, 1923..... .... 26 10 6 =e 2 0 MOA! Yaeld. ..)..c-=- = aeele 39.9 33.4 33.8 9 44.4 35.8 27.0 Infestation November, 1924..... 64 55 wee 48 19 4 0 1925 Yield.......... 17.7 21.0 soe 20.1 23.0 26.6 28.2 Infestation November, 1925..... 343 aa 20 1 0 sone 0 1926 Yield.......... SAS 5 Baad 35.2 45.8 38.9 <5ab 26.6 Average Infestation 65 48 18 16 7 1 0 1 Average Yield...... 25.7 31.7 33.7 34.5 34.8 33. ~ wo or J & © 374 ILLinoIs NaTuRAL History SURVEY BULLETIN Here, as at other points, the early seedings have been severely dam- aged by the Hessian Fly during several seasons, so that the yields were greatly reduced. Though differences in yields are only partly due to the influence of the fly and partly to other seasonal factors, a comparison of the records for several years will show how large a part is played by the fly in early seedings. Plots seeded during the period of September 12—16, for example, produced more than 39 bushels per acre in 1923 and 1924, when the infestation was very light; but those seeded during the same period in 1919 and 1924, when the infestation was very heavy, produced only 23.4 and 21.0 bushels per acre, respectively. For this locality, the highest average yield has been obtained from plots seeded between September 22 and October 17, although a few plots seeded later than October 12 have given very good yields. Here again, as shown by the averages, the normal relatively fly-free date, September 26, corresponds very closely with the date of highest yield. See Figure 7. Date _oF S€EDING HEBEL Septlé-/6) |Sept 17-21 Sept22-24 [septeZOct Oct2-€ 8 UsKeL S PER ACRE N / Hie Wormal f/yt free cate) ts / / / we As) Oo Fig. 7. Graphs showing average yield and average infesta- tion for experimental plots in Hancock County. CHAMPAIGN COUNTY The date-of-seeding experiments on the University Farm in Cham- paign County were not started until the fall of 1919, but a very extended series has been carried out. Some very early and very late seedings, be- ginning with August 28 and ending with October 31, have been made since 1923. The results are shown in Table IV and Figure 8. While all the early seedings have made a good growth and the plants have borne large tops in the fall, the yields from them have not been as high as those from the later seedings. The highest average yields were obtained from plots seeded between September 27 and October 12, that is, within two weeks after the normal relatively fly-free date for this locality. ss THe HESSIAN FLy AND THE WHEAT CROP 375 In some seasons, however, October 12 is too late to prevent severe winter killing, and for this reason the best yield generally may be expected from seedings made between September 27 and October 6. The figures for the first two years are especially significant. In 1920, the lowest yields were obtained from the early-sown plots, which all be- came heavily infested by the fly, and progressively higher yields were ob- tained from the late-sown plots as the infestation decreased. In 1921, on the contrary, the relatively high infestation in wheat sown between Sep- tember 22 and October 1 was not of serious consequence because the in- festation occurred late, and the feeding of the maggots that were in the wheat in the fall was curtailed by cold weather, and they all died during the winter. Taste IV Per Cent INFESTATION BY THE HESSIAN FLy anp WHEAT YIELDS (BUSHELS PER ACRE) CHAMPAIGN COUNTY 1919—1927 | | | 7 | } | Date of Aug. Sept. Sept. Sept. | Oct. | Oct. | Oct. Oct. | Oct. | After seeding | song, 1| 12-16 | 17-21 22-26 | Get | 2-8 | 71 | 12-16 | 17—21 | 27—31 | Oct. 31 | | | Infestation November, 1919 .... 100 100 75 0 0 3 1920 Yield...... S95 23.3 28.5 40.3 43.1 37.9 : Infestation November, 1920 .... 100 100 100 95 38 0 0 1921 Yield...... Tees 33.9 32.3 33.1 37.1 40.3 39.1 34.7 Infestation a November, 1921 .... 16 5 0 S 0 0 0 0 e 1922 Yield...... 555 25.0 30.6 28.2 = 33.8 32.2 36.3 40.3 < Infestation = November, 1922 .... 1 0 0 g 0 0 0 0 1923 Yield...... a8 36.3 45.9 45.9 . 39.5 37.9 39.5 31.4 Infestation = November, 1923 13 2 5 0 0 0 0 0 1924 Yield...... 32.1 34.3 33.2 36.0 5 40.8 38.9 31.4 32.7 Infestation = November, 1924 7: 42 17 <=} 4 6 0 0 0 1925 Yield...... 15.9 20.2 21.2 17.4 3 34.1 41.1 38.6 31.4 21.6 = Infestation z November, 1925 93 sats 43 0 Zz 0 0 i) woke 0 - 0 1926 Yield...... 12.1 oe 20.4 35.3 34.0 32.7 33.1 aoe Rises aos 24.6 Infestation November, 1926 29 17 6 a4 oe eae 9 ee 6 8 0 1927 Yield...... 35.8 39.4 38.5 355 5355 ee SoeG geeen 32.4 33.0 28.5 Average Infestation .... 52 40 35 26 20 6 2 0 1 2 0 Average Yield.. 24.0 30.3 31.3 33.7 36.4 37.8 36.6 37.2 33.7 28.7 28.6 376 ILLINoIs NATURAL History SURVEY BULLETIN DATE OF SEEDING 50 =e [fo] Ts S i 6 4o 7 =~ | ® Pe) x S “ w N x S & lef : Xt 2 Ni Yie § \ i & a eS % Sit y & Sy ‘ oa, “4 S Q elon ek RS \ so [o=== 0 \ i) 2 ee Ss) Fig. 8. Graphs showing average yield and average infesta- tionfor experimental plots in Champaign County. Macoupin County The experiment in Macoupin County has been conducted for the en- tire period on the farm of Mr. Vernon Vaniman two miles south of Vir- den. Mr. Vaniman and his tenant, Mr. Theo. Anspaugh, have helped in every way in carrying on this experiment. Seedings were made as early as the middle of September and as late as the fourth week in October. The records for the eight years, as shown in Table V, are very good and may be relied upon as typical of conditions in that locality. The figures on average infestation over the whole period indicate that the Hessian Fly normally is most abundant there in wheat sown from DATE _OF SEEDING S a g Ss & ~ 4 N30 gos iS = x 9 320 aS 20 > Infesty ron - = wa) 2) 10 QO Oo Fig.9. Graphs showing average yield and’ average infesta- tion for experimental plots in Macoupin County. THE HESSIAN FLY AND THE WHEAT CROP 377 September 17 to 21, and progressively less abundant in wheat sown later. In certain years, however, notably in 1919, 1920, 1921, and 1925, plots seeded during September 22—26 became heavily infested and, on the whole, made very low yields. In every year except the first, when the flies were scarce throughout the season, the highest yields were obtained from plots seeded within a few days of the relatively fly-free date, Oc- tober 2. Figure 9 shows graphically this close relationship between fly in- festation and yield. The graph for infestation reaches its highest point at the same time as the graph for yield reaches its lowest point. Then, as the former falls, the latter rises, and after October 1, when infes- tation becomes negligible, the yield is comparatively high. It is evi- dent, therefore, that the best yields in this section can be expected, on the average, from wheat sown between October 1 and October 16. TABLE V Per CENT INFESTATION BY THE HESSIAN FLY AND WHEAT YIELDS (BUSHELS PER ACRE) MACOUPIN COUNTY 1917—1926 Date of Sept. | Sept. | Sept. | Soe Oct. Oct. Oct. Oct. seeding 12-16 | 17—21 | 22—26 Oct.1 2-6 7-11 12—16 17—21 Infestation November, 1917..... 10 ares 3 0 bor 0 0 AQIS) Vields oes... 46.8 eins 43.6 41.9 es 37.1 37.1 Infestation November, 1918..... mrece 28 16 0 0 0 Bee 0 1919 Yield.......... sien 14.9 17.3 17.4 2 20.9 19.4 naire 17.2 ‘ Nn Infestation 5 November, 1919..... 100 100 81 13 2 0 0 1920 Yield.......... 10.5 12.1 23.4 30.6 2 29.8 33.1 Infestation = November, 1920..... Rivets 94 88 85 ee 44 0 1921 Yield.......... he 13.7 11.3 AS of, yas) eS 17.8 16.1 Infestation Ss November, 70 50 SS 9 5 0 1922 Yield 11.3 12.9 “a 22.7 17.7 19.3 Infestation Ss November, 1922..... 2 1 = 1 0 TORRONE is cnwees 23.3 25.8 5 35.4 29.0 29.8 Zz Infestation November, 1924..... 33 17 20 19 0 0 1925) Wield cowcces ss 21.7 21.6 23.0 24.4 29.4 26.0 Infestation November, 1925..... Adee 68 55 0 0 0 0 iCpliy VaR Re nechso a500 43.6 37.4 52.6 43.7 34.8 47.7 Average Infestation. 48 54 39 19 14 7 0 0 Average Yield...... 26.3 20.1 24.3 30.1 28.3 25.3 30.3 29.0 378 ILLtinois NATURAL History SURVEY BULLETIN Marion County The plots for date-of-seeding experiments in Marion County were located during the entire period on the farm of Mr. Ben Michael, west of Centralia. Mr. Michael’s friendly cooperation has been enjoyed and is highly appreciated. During most of the period covered by these experi- ments, the Bureau of Entomology has had a man stationed there to de- vote his entire time to the Hessian Fly work, making observations not only on the degree of infestation in relation to yield, but also on the weather conditions which brought out the fly, the rate of parasitism, and the possible resistance of different varieties of wheat to the attack of the fly. In addition to the usual series, a number of very early seedings were made, beginning on August 28. TABLE VI Per Cent INFESTATION BY THE HESSIAN FLY AND WHEAT YIELDS (BUSHELS PER ACRE) MARION COUNTY 1919—1927 Date of Aus. | sept. | Sept. | Sept. | SeP& | oct Oct Oct. | Oct u 28 ‘ . | Sept. | Sept. 27 a et. et. et. seedingaa— Sept. 1 1216 | 17—21 | 2226 | oot 4 2-6 7-11 12—16 | 17—21 Infestation November, 1919........ male 96 patee 96 89 56 13 0 0 1920 Yield.....:........ ange 9.9 woe 14.9 11.2 14.9 10.6 9.8 10.9 Infestation November, 1920........ wate went 77 85 85 54 6 0 0 1921S Vieldecemem: ceeere. S008 SHOU 18.0 15.7 12.0 14.8 17.7 21.8 28.3 Infestation a November, 7. 56 S408 75 sas 17 & vi 0 0 1922 Yield 33.0 37.5 S05 36.4 Aad 35.0 3 30.1 29.0 29.8 Oo Infestation ° November, 1922........ 64 63 42 85 74 4 77 72 15 1923 Viel deen ee viene 10.0 14.5 14.5 16.5 14.0 » 16.0 21.0 22.8 oS Infestation is November, 1923........ 67 96 95 66 1 o 0 0 ever 19247 Vielqee eG sence = 1.5 2.0 2.5 6.5 26.8 = 21.0 25.5 5 ot Infestation S November, 1924........ 15 22 24 15 3 0 0 0 UPPE veel sosnasocecdee 22.5 29.5 29.0 35.0 & 34.0 32.0 34.0 o Infestation a November, 1925........ 56 59 94 49 0 0 0 0 1926 Yield.............. 8.0 10.0 8.5 20.5 28.0 26.0 23.5 26.0 Infestation November, 1926........ = 0 0 . 1927p Waelder: ees 23.0 14.0 = Average Infestation.... 66 64 89 62 71 31 13 9 3 Average Yield......... 13.1 16.1 9.7 19.7 17.2 24.1 22.3 22.1 25.3 ee THE HESSIAN FLY AND THE WHEAT CROP 379 The results as shown in Table VI and Figure 10 again indicate how directly the Hessian Fly affects the yield of wheat. It certainly is not merely an accident that the yield graph reaches high points whenever the infestation graph reaches low points, and vice-versa, throughout the ex- periment. The connection is unmistakable. The normal relatively fly-free date for this locality is October 5. Judging from the data on the experimental plots, one can generally expect the best yields of wheat in this section from seedings made be- tween October 4 and October 20. DATE OF SEEOING 4ug.28| Sep7 | Sept | Sepr | Sep7 | Sgor |Sept27) Oct | Oct | Ocr | Oct. oot] zie 7a 12-16 | 17-21 |22-26|Oct/ | 2-6 | 7-U |\l216| /72/ Oct 22-26 w 00 x “\ § AlN 4 7S. a BO, \ ¥ = w 4 \ Al 8 my v4 = / \ - v C Go s=- -+-—-~+y a \ w & x u su Q \—_—_+ 2 —__} oo Gg Ip festetion \ eS > Q SS Yrel7 8 ° : N Py 3 x = vs ioe S S K : ( : \ he 0 Fig.10. Graphs showing average yield and average in- festation for experimental plots in Marion County. RANDOLPH CoUNTY The experimental work in Randolph County was done in the vicinity of Sparta. It was started on the farm of Mr. H. B. McIntire and has been continued, since 1920, on the farm of Mr. W. M. Beattie, whose reliability and interest have aided greatly in carrying on the work. The dates of seeding range from September 22 to October 21. As will be seen by an analysis of Table VII, or by a glance at Figure 11, the yields have been about the same, on the average, for all dates of seeding. Leaving out of account the exceptionally high yield in 1921 from the earliest seeding, the data show that plots sown about October 7, which is the normal relatively fly-free date for this locality, have given the best average yield. The infestation percentages indicate that the fly usually is not abundant enough there to cause any considerable damage to wheat sown after October 4. In unusual years, however, such as 1919, seedings made during the first week in October may become heavily infested and may give low yields. 380 ILLinois NATuRAL History SuRVEY BULLETIN TABLE VII Per Cent INFESTATION BY THE HESSIAN FLY AND WHEAT YIELDS (BUSHELS PER ACRE) RANDOLPH COUNTY 1919—1927 BE ee ee Sept, rea Oct. Oct. Oct. Oct. are S 22-26 Oct. 1 2-6 7-11 12-16 17—21 Infestation November, 100 100 99 abat 13 2 1920 Yield 7.3 5.5 12.1 Saki 22.0 16.5 Infestation November, 1920............... 26 8 13 0 Apa 0 § IGPAL WEEN oancaddaseccarnods6 42.5 33.8 30.5 31.5 miaiets 35.0 3 ~ Infestation be : November, 1921..............- 35 39 18 S 4 0 MPD Nah ss seme gaesns coed 32.5 30.5 33.0 = 24.0 23.0 : oO Infestation On ; November, 1922.............. 9 16 23 @B 19 4 ; 1923 Mitel Clmemrenictarrs leit 12.5 16.0 16.5 o 20.5 17.5 ; Infestation = November, 1923.............. ech 8 0 rn 0 0 0 ‘ 1924 Vitel Glee ioe ciatelsiaielstniolaictel inte aaa 16.5 16.5 S 14.0 20.5 16.0 : Infestation & November, 1924.............. Sioc 29 1 = 0 0 0 ; (GPE ara lascndsntosceacaun sao resin 32.0 33.5 a $1.5 27.5 28.5 . iz \ Infestation S q November, 1925.............. Nae 20 0 a 0 0 : IPE WING asd sana sede Sfa0d0s5 det 17.5 20.0 19.5 22.0 Infestation : November, 1926.............. sone 7 0 0 0 0 P PY Nal eapeidd SooccscusdRhn 30b0 21.0 21.5 21.0 19.5 14.0 ; 7 Average Infestation.......... 43 28 19 4 3 1 ; Average Yield...........0+++ 23.7 21.6 23.0 23.8 21.8 21.6 f Dare of SEEOINS Sept 22-26] |Sept&7-Octl Oct2-6 | | Oct7 | | Octleré| |_Ocr/7Z1 | 50 (50 7 $ 40 40 © 5 2 y g Bm: Ss 3 Bs g N | Pr ss N = = : S 5 wre 8 Ki > 8 Infestation \ S 2 Q ‘ < 7 /0 AS 10 ‘ N Oo Fig.11. Graphs showing average yield and average in- festation for experimental plots in Randolph County. THE HESSIAN FLY AND THE WHEAT Crop 381 Jackson CouNTY The work in Jackson County has been done on several different farms in different years, under conditions that are hardly comparable. It has been interfered with by flooding of the plots, by winds, and by several other factors which have tended to confuse the results. In 1918, for example, when the plots were on rich bottomland that had been heavily treated with fertilizer, flooding interfered with cutting, so that the data had to be discarded. The results shown in Table VIII and Figure 12, therefore, cannot be considered as truly representative of this section of the State. The difference in the yields obtained from plots sown before the relatively fly-free date (October 7) and from those sown after this date, has been less than in any other county where the experiments were made. On the average, nevertheless, the best yields have been obtained from seedings made between October 2 and TABLE VIII Per CENT INFESTATION BY THE HESSIAN FLY AND WHEAT YIELDS (BUSHELS PER ACRE) JACKSON COUNTY 1918—1926 | | Date of | Sept. Sat Oct. Oct. Oct. Oct. | Oct, seedingaa 22—26 Oct 1 2-6 7-11 12—16 17-21 | 22-26 | | Infestation . November, 1918.. 2 1 0 0 0 0 1919 Yield....... 19.2 22.2 20.2 20.2 21.2 9.1 Infestation ‘ November, 1920.. 20 29 16 ~ 0 0 0 = 1921 Yield........ 6.5 12.1 10.5 = 9.7 8.1 6.5 : Infestation = November, 1921.. caus 65 33 ° 0 0 0 1922 Yield........ Bante 12.1 16.4 2 14.9 18.5 18.5 Infestation = November, 1922.. Noo 52 72 s 26 3 0 1923 Yield........ ees 3.6 4.6 s 6.4 4.8 11.2 Infestation = November, 0 0 S 0 0 1924 Yield... 13.0 16.5 a 16.5 20.6 24.6 Infestation E November, 1924.. 10 7 0 Zz 0 0 0 1925 Yield........ 24.1 29.7 30.7 35.0 27.7 24.5 Infestation November, 1925.. hae Hoty: 0 0 ssc5 0 1926 Yield........ sock aca 32.4 29.6 cece 26.9 Average Infestation ...... il 26 17 i) 5 0 0 Average Yield.... 16.6 15.5 18.8 21.0 16.8 15.1 18.1 382 Intinois NATuRAL History SURVEY BULLETIN October 12, though the yields from other seedings have not been much lower. More information on plots under more uniform conditions is needed in this locality before any definite conclusions can be drawn. Oare of SEEOING Db) INFESTATION PERCENT BusHets PER ACRE Yield ~ Ss Infestar) (7) Fig.12. Graphs showing average yield and average in- festation for experimental plots in Jackson County. PuLASKI CouNTY The date-of-seeding experiment in Pulaski County was made in cooperation with several different farmers in the vicinity of Grand Chain. Since 1922, the experiment has been located on the farm of Mr. A. J. Schoenborn, whose interest in the work has been a great help. Dare oF SEEDING INFESTATION PERCENT Busneys PER ACRE S 3 o Fig.13. Graphs showing average yield and average in- festation for experimental plots in Pulaski County. —— Tue Hessian FLy AND THE WHEAT Crop 383 The experimental plots have had very good attention, and the results shown in Table IX can be considered as representing average condi- tions in this locality. Most of the seedings were made between September 27 and October 26. In general, the best yields have been obtained from plots sown between October 5 and October 26. It will be noticed in Figure 13 that the yield graph reaches its highest point in the period of October 7—11, when the infestation graph falls to the 10 per cent mark. From this we may conclude that wheat sown within a few days after the normal fly-free date, October 8, will usually escape serious infestation. In the fall of 1922, however, when the fly was unusually late in making its appearance in this locality, wheat sown during the second week of October became heavily infested and made a low yield. TABLE IX Per Cent INFESTATION BY THE HESSIAN FLY AND WHEAT YIELDS (BUSHELS PER ACRE) PULASKI COUNTY 1919—1927 | | | Sept . | Date of Sept. eee | Oct. Oct. Oct. Oct. Oct. seeding {aS~ 22—26 Oct ees 2—6 i1 | 12—16 | 17—21 22—26 | | | | | Infestation November, 1919... 100 92 92 onan jo55 S855 0 1920 Yield........ 6.5 16.0 10.0 Eas cee Senc 15.5 Infestation November, 1920.. 10 0 0 6 0 0 0 iP O aS aces 14.0 7.5 9.0 15.5 12.0 13.5 14.0 Infestation o November, 1921.. 19 12 ba 0 0 0 0 1922 Yield........ 20.0 18.5 3 28.5 25.5 26.0 24.5 Infestation x November, 1922.. 25 38 39 = 68 28 7 1923 Yield........ 18.5 23.5 17.5 Se 16.5 19.5 16.5 Infestation = November, 1923.. Berg atin 36 a 0 0 0 1924 Yield........ SBo0 S05 17.5 2 25.0 32.5 26.0 Infestation 2 November, 1924.. ae seme 15 = 0 0 0 1925 Yield........ dae Saae 11.0 = 13.0 11.5 7.5 I Infestation z November, 1925.. 0 0 0 1926 Yield........ 36.0 35.5 28.8 Infestation November, 1926.. An Both ll 4 0 0 1927 Yield.:...... anes ash 17.5 15.0 11.0 9.0 Average Infestation ...... 45 37 26 10 0 3 1 Average Yield.... 13.0 16.8 17.1 21.3 18. on = “I ~ © wo 384 I~tinois NATURAL History SuRVEY BULLETIN SUMMARY Table X shows the average yields of wheat obtained from all seed- ings made before, and from all those made after, the normal relatively fly-free date for each of the localities named. In every locality, with the exception of Randolph and Jackson counties (see pp. 379-382), there has been an appreciable increase in the yield from the later seed- ings as compared with the earlier seedings. In most cases the increase in yield is sufficient to pay an added return equal to, or greater than, the taxes on the land. This increase does not involve any additional labor or any expenditure for fertilizer or any other outlay. From Table X, which also gives the average per cent infestation by the Hessian Fly in these two groups of seedings, it will be seen that the wheat sown after the relatively fly-free date has not been sufficiently infested at any point in the State to cause a marked decline in yield. In all the fields except the one in Marion County (Table V1), seedings made on the normal fly-free date have been relatively free from infes- tation throughout the entire period of the experiments. In a few sec- tions of the State it seems safe to make seedings a little earlier than this date in years when the Hessian Fly is known to be comparatively scarce in those particular localities. Early seeding does not produce high yields of wheat on the aver- age. The same is true of very late seeding. In years when the Hessian Fly is abundant, it is almost sure to cause a very marked decrease in yield from wheat sown early. The TABLE X AVERAGE YIELDS OF WHEAT (BUSHELS PER ACRE) AND PERCENTAGES OF PLANTS INFESTED BY HESSIAN FLY IN PLoTS SOWN BEFORE AND AFTER THE NORMAL RELATIVELY FLy-FREE DATE INCLUDING ALL YEARS COVERED BY EXPERIMENTS Number AVERAGE YIELD AVERAGE INFESTATION Location of plots of from wheat sown in wheat sown years BEFORE AFTER | BEFORE AFTER Winnebago County! .............. 6 24.8 28 1 17 2 LaSalle County? ..........---2.0+ 9 29 8 34.4 39 8 Hancock County................+ 9 32.0 35.0 33 3 Champaign County............... 8 30.6 34.8 44 5 Macoupin County 8 24.8 27.7 40 6 Marion County.. 8 17.8 23.0 60 8 Randolph County 8 22.5 22.3 28 2 Jackson County.. 7 17.0 17.2 19 il Pulaski County.. 8 16.2 19.2 33 4 AVERAGES (weighted by years) 25E1 27.4 36 4 1 Boone County, two years. 2 Bureau County, three years. THE HESSIAN FLY AND THE WHEAT CROP 385 results obtained from the experimental plots in such years are sum- marized in Table XI, showing that the difference between the yields from wheat sown before the fly-free date and after this date has aver- aged more than five bushels per acre. TABsLe XI AVERAGE YIELDS OF WHEAT (BUSHELS PER ACRE) AND PERCENTAGES OF PLANTS INFESTED BY HESSIAN FLy IN PLots Sown BerorRE AND AFTER THE NORMAL RELATIVELY FLY-FREE DATE EXCLUDING YEARS OF SLIGHT INFESTATION Number AVERAGE YIELD | AVERAGE INFESTATION Location of plots of | from wheat sown | in wheat sown years BEFORE AFTER | BEFORE AFTER Winnebago County? .............. 2 17.6 16.9 43 6 Masalle! County i. cn. ..cce eens 7 28.1 32.2 46 10 PANCOck: (OCOUNGY ssc. ccs cece cecae 3 24.0 29.3 65 11 Champaign County. 4 25.7 34.4 65 11 Macoupin County. dj 4 22.8 2S 67 12 Wa nvorie COU GV ters lccaicietesinncls saree 6 16.2 21.8 66 ll Randolph 1 County. .cecices cece 3 18.3 20.6 49 7 Jackson ‘County... .cccsccseeeces 2 9.2 12.4 55 5 PLUS MO OU Este xis nelasteten sireie me 2 15 3 17.0 64 26 AVERAGES (weighted by years) PNP) 25.6 58 11 1 Boone County, one year. * Bureau County, two years. In view of the very definite relationship between infestation and yield, the Hessian Fly cannot be disregarded as a factor in wheat pro- duction in Illinois, but must be Conadered every year. The entomologists of the State Natural History Survey and the Federal Bureau of Ento- mology cooperatively make a special Hessian Fly survey of Illinois each season during August, and the results of this survey, giving the relative abundance of the fly in all of the principal wheat-growing sections of the State, can be obtained by writing to the chief entomologist of the Natural History Survey at Urbana or through the Farm Bureau in each county. With this information at hand, growers should use their own judgment in regard to the time of seeding. ACKNOWLEDGMENT This work was made possible through the assistance of a number of entomologists connected with the field station of the Bureau of Ento- mology at Lafayette, Indiana, and the entomologists of the Natural His- tory Survey. Thanks are also due to the department of agronomy of the Illinois Agricultural Experiment Station for threshing all wheat samples from the experimental plots. STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVII. BULLETIN Article XII. The Bottom Fauna of the Middle Illinois River, 1913-1925 Its Distribution, Abundance, Valuation, and Index Value in the Study of Stream Pollution R. E. RICHARDSON PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS December, 1928 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVIL. BULLETIN Article XIL. The Bottom Fauna of the Middle Illinois River, 1913-1925 Its Distribution, Abundance, Valuation, and Index Value in the Study of Stream Pollution BY R. E. RICHARDSON PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS December, 1928 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. SHELTON, Director BOARD OF NATURAL RESOURCES AND CONSERVATION A. M. SHELTON, Chairman WILLIAM TRELEASE, Biology JoHN W. ALvorpb, Engineering Henry C. Cowes, Forestry CuHartes M. TuHompson, Representing Epson S. Bastin, Geology the President of the University of WittiAM A. Noyes, Chemistry Illinois THE NATURAL HISTORY SURVEY DIVISION STEPHEN A. ForsBes, Chief ScuNepp & BARNES, PRINTERS SPRINGFIELD, ILL. 1928 83820—1200 FOREWORD The present article is the twenty-third of a series of bulletins strictly devoted to Illinois River biology, containing 2108 pages and 155 plates, published during the past 52 years by the Illinois State Laboratory of Natural History and its successor, the State Natural History Survey, as a product of operations carried on from 1874 to 1927. It was the guiding purpose of these studies to make a comprehensive survey of the plants and animals of the stream and its tributary waters, and to analyze their interactions with each other and with their physical environment during all seasons of the year and under the various condi- tions of successive years, especial attention being paid to food relations and to effects produced upon the biological system of the stream by the periodical overflow and gradual recession of its waters—a phenomenon of which the Illinois offered a notable example owing to its generally sluggish current and the unusual extent of its bottomlands. During the early years of this period especial attention was given to the fishes of the stream and its connected waters, but not to the exclusion of the other inhabitants. In 1894 these preliminary studies, which were a part only of a gen- eral program covering the entire state, were concentrated and adequately provided for by the establishment of a biological station, with a complete- ly portable equipment, at Havana on the Illinois River, at which place continuous investigation was carried on from 1895 to 1900, supplemented by a summer’s operation with Meredosia, 47 miles below, as its center, and by a year’s work on the upper river for which the station equipment was moved to Ottawa in 1901. The Illinois River operations were there- after limited for a time to occasional visits while the other streams of the state were being explored and a report on the fishes of Illinois was being prepared and published, but continuous operations on Illinois River bi- ology were resumed in 1909 and were carried on with only occasional in- terruptions until 1925. The time necessary to accomplish the purposes in view was greatly prolonged by the repeated occurrence of revolutionary changes in con- dition, affecting the biological system of the river so profoundly as pres- ently to render obsolete much that had been done and to call for a repeti- tion of a considerable part of the work. The most important of these changes were, first, the introduction in 1885 of the European carp and its rapid multiplication, until by 1908 its yield to the commercial fishermen was greater than that of all the other fishes of the river taken together ; second, the completion and opening in January, 1900, of the drainage canal of the Sanitary District of Chicago, greatly increasing the amount [387] of raw sewage from the city of Chicago introduced into the Illinois at its source; and, third, a general movement for the reclamation of the bottomlands of the river for agricultural uses, by the construction of levees to prevent an overflow of the streams and by the drainage of bot- tomland lakes. Our biological studies of the Illinois River have, of course, been carried on by the aquatic biologists of our own staff, but for a knowledge of the ecological conditions of an aquatic situation, an acquaintance with the chemistry of the water was essential, and this has been made possible to us by the generous cooperation, at first of the Department of Chemis- try of the University of Illinois, which began analyses for us in May, 1894, and since then by the Water Survey of the State which was organ- ized the following year. These chemical studies became increasingly important as problems of stream pollution grew in prominence and led to the addition of a chemist to the river field party during the summer season of three years (1911, 1920, 1922), to the analysis of weekly samples sent to the chemical laboratory in 1914, and to occasional trips to the river in other years by chemists of the Water Survey, as called for by the biologists; and finally, upon the transfer of the main oper- ations of the Natural History Survey to Rock River in 1925, the State Water Survey took over the Illinois River program as a problem in river pollution, with its center of operations at Peoria, to which the Havana equipment had been transferred in 1920. The Natural History Survey still retains a permanent interest in the Illinois River, especially as a field for the solution of individual prob- lems ; and it dealt with one such problem in 1926 and 1927, when it made an exhaustive study of a new and remarkable disease of the European carp, traceable to the effects of pollution on the food supply of the carp. The Survey sustains also relations of cooperation with the Water Sur- vey, to which it furnishes a biologist whenever his services are likely to be needed in elucidation of chemical conditions disclosed. The place of the present bulletin in the series of which it is, in a sense, the final number, dealing as it does with the last twelve years of our active period on the Illinois, and discussing topics related to the whole range of our studies, may be made more evident by reference to the list of publications on the subject printed as an appendix to this paper. STEPHEN A. ForRBES. [388] a ee eee so CONTENTS PAGE aera Oran Dia Ste Puen! AC MBOLDES ca 5 2 ssc -s,c.0-5,5% soe be.t cen on ae 387 Collections, dates, apparatus, river levels. ..........:..5-.----.-- 391 River reaches covered, main hydrographical features, and principal SOMecineistaHansy |\withtimapy': cet acloe tc aadercces saiawcdee ees eRe Load of sewage and industrial waste and zones of pollution [with altel eee ete aricr ocrc Abe ncfaa Are entero ra Feed wares ah cher ase Se OOO Classification of the species with reference to degree of tolerance... 403 Some principal points regarding index value..............-....-- 410 Changes in the number of species taken and missing..............- 414 Changes in the dissolved oxygen supply..................+-.+..- 420 Major changes in abundance of the more important groups......... 425 Changes in valuation as fish food and in per cent composition by WHEE. seg. o 5 2 IRE Seta rls So is Be Ines ti See nero 432 Temporal succession of the leading groups of pollutional or unusual- ly tolerant forms in the polluted reaches below Chillicothe. ....... 437 Gogineiid yeenelaliQuspe er) cae coredes eel sae ese 2 se eats oe ee 442 Accessibility, quality, and extent of use as fish food............... tit Changes in abundance of the principal groups during and just after They conunious»summer floodsor 1924—.: ..js cee Sk eee ue ee eee 448 Comparative abundance in the channel and extra-channel areas, 1920 (ko) UN ole SS ES oe ee Sic ae ese Ione ene IE eee eR eee 453 Changes in the mussel fauna of Peoria Lake, 1912 to 1925......... 454 Becplanawonmnoter ChueralgaMlesechrch Jas) scesic asec See oe aie soe © ar 458 SHAME Bete s SY Shoes DOOR OCIS Re cea ann area 469 JARDEINGIS.S: 553.5455 no oOo ESR A OMe ES erSe f be GEC ae eee ae 473 [389] : a ¢ % * Dak: ns utes Lae ei: Rau aor ce See A aver Cee a ee i } AN Shee ea mow ele tie ‘ at vas: > rai A Sp i i ncn Ae ’ ; we SSAC aS whe gia-leeN phe gil el os VoLtuME XVII ARTICLE XII THE BOTTOM FAUNA OF THE MIDDLE ILLINOIS RIVER, 1913-1925 Its Distribution, Abundance, Valuation, and Index Value in the Study of Stream Pollution R. E. Richardson The present paper adds the findings of two more years (1924 and 1925) to our previous accumulation* on the small bottom fauna oi the middle Illinois River, and brings into comparison with the data obtained under the comparatively clean-water conditions of 1913-1915 the results of five summers’ collecting in the more or less seriously polluted bottom muds in the same territory between the years 1920 and 1925. The dis- solved-oxygen readings for the same or neighboring years have been fur- nished by the Illinois State Water Survey. The collection of the bio- logical material in 1923 was the work of Dr. D. H. Thompson of the Natural History Survey. The same part of the work in 1924 and 1925 was in the hands of Dr. H. J. Eigenbrodt. Especial thanks are also due to Dr. Thompson for considerable clerical work in the organization of recent data, and for valuable suggestions in the course of preparation of the manuscript. Collections, Dates, Apparatus, River Levels The statements contained in the present paper concerning the changes in the Illinois River bottom fauna during the twelve-year period, 1913- 1925, are mainly based on a total of 749 dredge and Petersen sampler collections taken between Chillicothe (146.5 miles below Chicago) and the Lagrange Dam (249.5 miles below Chicago). Of these, 237 hauls, with various dredges or with the mud dipper, were taken during the three years 1913-1915. The remainder, 512 collections with the Petersen samp- ler, were taken during the summers of 1920 and 1922-1925, covering five * Richardson, R. E., The Small Bottom and Shore Fauna of the Middle and Lower Illinois River and its Connecting Lakes, Chillicothe to Grafton; its Valua- tion; its Sources of Food Supply; and its Relation to the Fishery. Bull. Ill. Nat. Hist. Survey, Vol. XIII, Art. XV, pp. 363-524, and maps; June, 1921. —————_.,, Changes in the Bottom and Shore Fauna of the Middle Illinois River and its Connecting Lakes since 1913-1915 as a Result of the Increase Southward of Sewage Pollution. Bull. Ill. Nat. Hist. Survey, Vol. XIV, Art. IV, pp. 33-75; December, 1921. —————.,, Changes in the Small Bottom Fauna of Peoria Lake, 1920 to 1922. Bull. Ill. Nat. Hist. Survey, Vol. XV, Art. V, pp. 327-388; August, 1925. ————., Illinois River Bottom Fauna in 1923. Bull. Ill. Nat. Hist. Survey, Vol. XV, Art. VI, pp. 391-422; October, 1925. [391] 392 ILLInoIs NAtTuRAL History SurRvVEY BULLETIN seasons. The 749 collections mentioned were all taken either in the river proper or in the extra-channel portions of the expanded river above Peoria known as Peoria Lake, but include none from the smaller, more nearly inclosed, but connecting, bottomland lakes below or above Peoria. The distribution of these 749 collections in time and their apportionment to river reaches was as follows: Number of collections 1913 Chillicothe to Lagrange Dam........ 44 1914 Vicinity ot blavaiiawerenia-int sat eens 13 1915 Chillicothe to Lagrange Dam........ 180 1920 Chillicothe to foot of Hickory Island. fal 1922 Chillicothe to foot of Peoria Lake... 71 1923 LaSalle to Beardstown............. 158 1924 LaSalle to Beardstown............. 137 1925 LaSalle to Beardstown............. 75 Total aie Meronacsct erie tetneunrie 749 In addition to the above collections from the river and Peoria Lake there were taken in the river below Lagrange Dam in 1913 and 1915 a total of 153 hauls with dredges; and in the connecting bottomland lakes between Clear Lake (about 10 miles above Havana) and Meredosia Bay between 1913 and 1920 a total of 406. The apportionment of these col- lections follows: Number of collections 1913 Illinois River, Lagrange Dam to Graf- ton (mouth of river)............ 78 1915 Illinois River, Lagrange Dam to Graf- rea SEOUIS SU eetuaws tastes varepap ie eteuen ee iare aan stie gems 75 1913 Connecting bottomland lakes, Clear Lake to Meredosia Bay.......... 113 1914 Connecting bottomland lakes, Clear Lake to Sangamon Bay........... 102 1915 Connecting bottomland lakes, Clear Lake to Sangamon Bay.......... 171 1920 Connecting bottomland: lakes, Liver- pool Lake to Stewart Lake........ 20 Bortom Fauna, ILtinois River, 1913-1925 393 Adding this group of bottom collections to the first list given, we have a grand total of 1,308 dredge and Petersen sampler hauls taken between 1913 and 1925 in the Illinois River and immediately connecting waters ; 406 of these coming from the smaller connecting bottomland lakes below Peoria; and 902 from the river proper and Peoria Lake. The usual collecting period, in all years, has been June to Septem- ber, with the larger part of the work falling in July and August. In the 1913-1915 period a small number of spring collections were taken, and in the autumn of 1914 work was extended to the end of October. The collections of the small bottom fauna in 1920 and 1922 were made without exception in the deeper open water, both of Peoria Lake and of the river, being thus confined to those areas where the effects of pol- lution were felt most fully, and where there was no unusual aeration or other protection afforded by coarse aquatic vegetation. In 1923, 1924, and 1925, a few collections were made near the margins, in the rather sparse new growths of vegetation since 1920, but the data from those lots are excluded from the figures used in valuation, and the species there taken are segregated for special treatment in the arrangement of the lists of species taken in order of index value, and their discussion. Weed and edge species have been excluded also from all 1913-1915 data used for comparison. River levels during all but two of the eight seasons of collecting from 1913 to 1925 were either unusually low or about average for the warm season of recent years. The summer of 1915 was unusually wet, but ap- parently not sufficiently so to affect seriously the distribution or the abund- ance of the bottom invertebrates. The summer of 1924 had several suc- cessive floods that seem to be reflected in the bottom fauna figures for that year. For a brief further.statement on river levels, and some ac- count of the effects of the floods of 1924 on the small bottom animals, see page 448. River Reaches Covered, Main Hydrographical Features, and Principal Collecting Stations The portion of the Illinois River north of the Lagrange Dam coy- ered either by the collections of 1913-1915 or by those of 1920-1925, or in both periods, has a length of 148 miles, lying between mile numbers 101.5 and 249.5 below Lake Michigan, or between LaSalle and the Lagrange Dam, respectively. This region of river breaks naturally into three main sections: the first, the 45 miles between LaSalle and the approximate head of Peoria Lake at Chillicothe; the second, the 19.9 miles of greatly expanded river between Chillicothe and the Peoria and Pekin Union Railway Bridge at South Peoria, which we have assigned to Peoria Lake; and third, the 83.1 miles between the Peoria and Pekin Union Railway Bridge, or foot of Peoria Lake, and the Lagrange Dam. 394 Iutrnois NaturaL History Survey BuLLeTIN The 45-mile reach, LaSalle to Chillicothe, is mainly a sluggish, black-mud-bottomed section, with no important tributaries or other varying hydrographical features, except for the low dam at Henry, about three-fourths of the distance downstream from LaSalle. The effect of this dam is not important at either present or recent low-water stages, the swifter current immediately below continuing an almost negligible distance into the region of exceedingly low slope between there and Chil- licothe. The 19.9-mile section called Peoria Lake is made up, first, of two unusually wide and sluggish, mud-bottomed lakes or “wide-waters” (Upper and Middle Peoria Lake), about 7.7 and 6.8 miles in length, respectively ; differing scarcely perceptibly in hydrographical character; and separated by a wide “narrows”, of visibly faster-moving water which covers a distance of around three-quarters of a mile and has mud bot- tom. The lower 5.4 miles of this 19.9-mile section (Lower Peoria Lake) is both shorter and narrower than either the Upper or Middle Lake; has a distinctly swifter average current, relatively much wider channel and correspondingly narrower “lake” or ‘“‘wide-water” portion; and is separated from the Middle Lake, at Peoria Narrows, by a narrow neck about one-half mile in length, with unusually fast current and generally well washed, lightly silted, and Bryozoa-covered bottom. The 83.1 miles between the. foot of Peoria Lake and the Lagrange Dam presents a great variety hydrographically, having alternating swift and sluggish reaches, a dam (Copperas Creek) about one-fourth of the way down, two tributaries of considerable size (Mackinaw and Spoon Rivers, the first important ones below LaSalle) between Peoria- Pekin and its midway point, and another still larger tributary (Sangamon River) about 10 miles above its lower end. For purposes of conven- ience, mainly, we have broken it up, in various comparisons, into five sections; the first four being short ones, covering only the first 40.6 miles below the foot of the Lake and ending just below Spoon River at Havana; and the fifth covering the entire remaining 42.5 miles be- tween Havana and the dam at Lagrange. The four upper short reaches recognized between the foot of Pe- oria Lake and Havana, in their turn, break into two groups at the Cop- peras Creek Dam, 23.8 miles below the foot of Peoria Lake. The upper 23.8 miles, again, has a natural break at Pekin, due to the access there of large additional factory wastes and to the marked slowing up of current that begins very shortly below that point as a consequence of the backing effect at low water of the Copperas Creek Dam. Also, the 16.8 miles between Copperas Creek Dam and Havana has a more or less natural dividing line about one mile above Liverpool, marking roughly the complete subsidence of the faster flow following the fall over the crest of the dam, and the entrance into the very sluggish deep- soft-black-mud-bottomed pool lying between that point and the Spoon River bar about 9 miles south. 4 q 4 : i | | : | Borrom Fauna, ILtinors River, 1913-1925 395 The stretch of 42.5 miles between Havana and the Lagrange Dam covered in the seasons 1913-1915 is much more uniform over most of its length than the Peoria~Havana section. Sand, sand and shell, hard clay, or very lightly silted soft bottom is the rule throughout this stretch with the single important exception of a few miles of more heavily silted bot- tom lying immediately above the Sangamon River bar, about 5 miles above Beardstown and about 15 miles above Lagrange. The scheme of main reaches and subdivisions and a list of the principal sampling stations, or location of cross-sections, with distances below Lake Michigan, will be found in Tables I and II, respectively. TABLE I Marin REACHES AND SUBDIVISIONS OF TIE ILLINOIS RIVER CovERED BY COMPARABLE BorTroM FAUNA SERIES, BOTH 1913-1915 aNp 1920-1925 | Upper and lower Reaches and subdivisions Ae a mile numbers (below Lake Michigan) Chillicothe to Foot of Peoria Lake........... 199 146.5—166.4 MBER CORE Micdkee iste okie eens tele cele vercsaei is Tet 146.5—154.2 Mid dlemPeoniaisabes. Given aii ccs ele ticles 6 6.8 154.2—161.0 OW erm PEOT a Isa KOre.. «yes «cosre's 01s cheers ee pss 5.4 161.0—166.4 Foot of Peoria Lake to Lagrange Dam....... 83.1 166.4—249.5 or Foot of Peoria Lake to Beardstown....... 71.6 166 .4—238.0 Foot of Peoria Lake to Copperas Creek DENIM terror ararcrsint pee scarce saves uatsccta ara 23.8 166.4—190.2 Foot of Peoria Lake to Pekin........ 7.6 166.4—174.0 Pekin to Copperas Creek Dam....... 16.2 174.0—190.2 Copperas Creek Dam to Havana.......... 16.8 190 .2—207.0 Copperas Creek Dam to 1 Mile above EVEL BOO ertrtereeicmaeyeishelst eit nteciciniers 7.8 190.2—198.0 1 Mile above Liverpool to Havana.... 9.0 198 .0—207.0 Havana to Lagrange Dam............... 42.5 207 .0—249.5 or Havana to Beardstown..............- 31.0 207 .0—2388 .0 396 Intinois NaturAL History Survey BULLETIN TABLE II LocATION OF PRINCIPAL SAMPLING STATIONS (Bottom Fauna AND DISSOLVED OxyGEN) Ituinois Rrver, 1913-1915 ro 1925 Distance below Lake Michigan Sampling stations Fa aastros * BA Salve eples, spo eercs ee acer cea cll atere te eR meme 101.5 Springs) Valley. .G. krcon tet -eheeteekeoe moon tae 108.6 FOnMepins Hitec ney erie ciecahelaiaterci wen reeeieieetters 119.5 ERGOT TY. © foi seh recstere iets Gr ekcnscet aks haniee he accu whecthe enoeeehe 131.0 SACOM crest ot ag iste oe eee hare eae 137.8 Chillicothes Geis 2vintencce oes teccyaepiare tan eattais 146.5 FROME! FP are Spake coarsttvavelebere antares aRTae ete oe 149.3 Foot of Partridge Island.................. 151.0 Upper Peoria Lake Spring? Bayer sclsistoees stat nie Sheual er astane serersce 153.2 Spring) Bay Narrows: sacs se eee 154.0 Mossivallle: = Ssh 5 soreednte. ie croconelettnetee tare Gune-Ave) (01677 Enea Middle Peoria Lake: Mossville .......... 1,98 Guwy-Aug.) “78 Gune-Aug:) 1977? 3.017 (July-Aug.) 4.802 (June-July. 3.068 (July-Sept.) * Exponent is number of readings averaged taken in the months indicated. yj Water levels, all years, about normal for season. Visible increases in the bottom In Lower Peoria Lake and in dissolved oxygen in mid-channel between Copperas Creek Dam and Beardstown after 1923. the river between Wesley (opposite South Peoria) and points shortly above Copperas Creek Dam the mid- summer dissolved oxygen readings since 1920 have generally been quite irregular and are best left out of the Bottom Fauna, Ivirvois River, 1913-1925 423 discussion at present. The first low, then high figures encountered, at various stations in this section of the river, sometimes reversed on the next round, are a consequence of the always varying mixture of fresh sewage received at Peoria and Pekin with more or less highly oxygenated water received from the frequently rich plankton-bearing wide-waters of the middle and lower sections of Peoria Lake. Omitting these figures, and dropping about 31 miles below the foot of Peoria Lake, to Liverpool, we find again for the 40-mile section of river between Liverpool and Beardstown readings that are as a rule much more regular and certain in significance, but have relatively fewer of them for the summer months since and including 1920, than were taken in Peoria Lake. Taking Liver- pool, Havana, and Beardstown, 31, 40, and 71 miles below the foot of Peoria Lake, approximately, as representative stations for this section, we note little change upward, or actual decrease in the amounts of bottom oxygen present between 1920 and 1923; averages or single samples taken at the three stations in July-September of those two years running: Liver- pool 1.75° in 1920* and 0.0' parts per million in 1923; Havana 2.16% parts per million in 1920, and 1.17 in 1923; and Beardstown 2.2! in 1920 and 2.44 in 1923. Between 1923 and 1925, however, an emphatic upturn in the bottom dissolved oxygen is indicated by our rather limited number of mid-channel readings from these same three stations. The comparisons with 1920 stood: Liverpool, increase from 1.75? to 4.45? parts per million; Havana from 2.16° to 4.60° parts per million; and Beardstown from 2.2? to 3.3 parts per million. It appears likely, though not wholly certain, that the increases at Liverpool and Havana between 1923 and 1925 reflect improve- ment in methods of waste-disposal recently put into operation by the Corn Products Refining Company at Pekin; and that the moderate relapse in the dissolved oxygen figures at some stations below Havana in the sum- mer of 1923, as in other recent years, is a consequence of delayed fer- mentation of some of the carbohydrate wastes still received at Pekin or Peoria. TABLE X. CHANGES IN Bortrom DISSOLVED OXYGEN, MIbD-CHANNEL, LIVERPOOL TO BEARDS- TOWN, 1920 To 1925; Parts PER MILLION*7 Sampling stations 1920 1923 1925 Thi erpoolen saa. fo scer<-s2 1.751 (Aug.-Sept.) 0.0! Aug.) 4.452 Guly) IRENE Aye cicisict's mp aisins few yoaG uy neee) 1 4.67 Guly) Beardstown ..........-- 2.91 (Sept.) 2.41 (Aug.) Sess) * Exponent is number of readings averaged. 7 Water levels, all years, about normal for season. 424 Intinois NATURAL History SURVEY BULLETIN Uncertain index value of dissolved In the suminer months of oxygen figures from the Peoria Lake 1920 and succeeding years dis- qwide-waters since 1920. solved oxygen readings from the wide-waters of Upper and Mid- dle Peoria Lake have agreed mainly in the single point of showing great irregularity. This is, however, not wholly unexpected, as both these sec- tions of expanded river lie in close proximity to the boundary line between the light and the heavy oxygen-producing plankton of the warm low-water period (in other words, the blue-green Algae and the chlorophyll-bearing Algae and Flagellata). The location of this line in 1920 and 1922 varied sometimes as much as the length of either lake in a few days or weeks, as there occurred shifts in water levels, temperature, wind, and sunlight. Under the most favorable conditions for the multiplication of the Chloro- phyceae and the green Flagellata, we occasionally obtained in 1920, even in the wide-waters of the Upper Lake, surface readings of dissolved oxy- gen topping 6 or 7 parts per million. A few days or weeks later, as the lower limit of the largely colorless or blue-green plankton moved several miles further downstream, it was not unusual to get bottom readings under one part per million more than three-quarters of a mile from mid- channel in the Upper Lake; and readings under two parts per million at similar distances even in the lower part of the Middle Lake. Because of this unusually great variability in dissolved oxygen fig- ures, the minimum mid-summer readings are believed to be of more value than averages in estimating the fundamental or underlying sanitary con- dition in the Peoria Lake wide-waters. A short table of minimum dis- solved oxygen readings taken at long distances from the mid-channel line in the Upper and Middle Lakes is shown on p. 425. For comparison with the location of these minimum readings, the approximate full recent low-water widths of the lake on the side beyond the mid-channel line from which they were taken are also given. These show that at times both in the summer of 1920 and 1922 comparatively low bottom dissolved oxygen was not infrequent at stations well toward the margins of the east wide- waters of these two subdivisions of Peoria Lake. The 1924 figures are of no value for comparison because of excessive dilution due to flood conditions all summer. The 1925 unpublished fig- ures by the State Water Survey are apparently deficient in readings from stations at long distances from the center of the channel, in all sections of Peoria Lake. Although this is the case, it is believed it may safely be assumed that, as there was practically no change in the channel supply of bottom oxygen in the Upper and Middle Lakes between 1920 and 1925, so there cannot have been any appreciable amount of change of a permanent nature in the wide-waters, at least where open and compara- tively free from vegetation. During the summer season, our recent records of dissolved oxygen, both surface and bottom, in the east wide-waters of Lower Peoria Lake have in general been more consistently high in comparison with the indi- cations supplied by the bottom fauna than in either the Upper or Middle Borrom Fauna, Invtrnois River, 1913-1925 425 Lake. But this advantage is probably largely nullified at other seasons, as in the late autumn, when the first northwest winds carry over local pol- lution from the Peoria water front. Effects of this wind- and wave-borne pollution are apparent, in fact, on comparison of the number of small bot- tom animals with lowest tolerance taken in recent years in the Middle and Lower Lake. It is found, in brief, that if a few species that have survived in the Lower Lake since 1920 by virtue of unusual current of the very wide channel be excepted, the Middle Lake has recently yielded a larger number of small bottom species with low tolerance than has the Lower. TABLE XI. Borrom DIssoLveD OXYGEN, Mip-SUMMER LOW POINTS IN PEORIA LAKE WIDE-WATERS, 1920 AND 1922.* Approximate " rantwiaen | tame | of lake Chen ncieting Low readings east of of foe isayniguan of bottom Reaches and stations Year mid-channel dissolved Gissolved line at recent oxygen summer low sienaee water levels = p. p.m. miles miles Upper Peoria Lake ROMIGI re oiveneicies se apes 1920 0.87 0.75 1.5 July FROIMIGY aha ee cists cisterns ices 1920 0.87 0.62 2.0 Aug. ERED ERT beste avai ates aratang 1922 0.87 0.70 1.0 Aug. Rome, 2% mi. below 1920 0.87 0.62 2.7 July Rome, 2% mi. below 1920 0.87 0.83 0.4 Aug. Middle Peoria Lake IMOSSWIGD Sree cee me 1922 0.87 0.60 3.0 Aug. Mossville: fess. > 1920 0.87 0.75+ 3.1-3.4 July Mossville, %4 mi. below 1920 1.00 0.62 2.0 Aug. 19 Aug PAISSERGSGCD) vost encis