Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. [ SNT OF AGRICULTURE N Se SiN NO; 144. = = <> . BILAxrovs PAPERS. - ety ~. ATION 0 oF NICOTINE TO THE BURNING QUALITY OF TOBACCO. By WIGHTMAN W. GARNER, Scientific A = Ac Tobaceo Tiivestigations. Se ~< ssistant, ss 4 oh a THE GRANVILLE TOBACCO WILT. Se By ERWIN F. SMITH, Pathologist in Charge of the Sera _ Laboratory of Plant Pathology. aa" mh ‘THE FLoRiDA VELVET BEAN AND ITS HISTORY. y KATHERINE STEPHENS BORT, Laboratory Aid, 3 2 ee - Forage Crop Investigations. Ae 1. THE IMPORTANCE OF BROAD BREEDING IN CORN. # te oe By GN. COLLINS, Assistant Botanist. ane = r HE PRESENT STATUS OF THE CHESTNUT-BARK DISEASE. - METCAI F, Pathologist in Charge, and J. FRANKLIN COLLIN i ee Agent, Investigations i in Forest Pathology. = DEPARTMENT OF AGRICULTURE. BUREAU OF PLANT INDUSTRY— BULLETIN NO. 141. B. T. GALLOWAY, Chief of Bureau. MISCELLANEOUS PAPERS. I. THE RELATION OF NICOTINE TO THE BURNING QUALITY OF TOBACCO. By WIGHTMAN W. GARNER, Scientific Assistant, Tobacco Investigations. Il. THE GRANVILLE TOBACCO WILT. By ERWIN F. SMITH, Pathologist in Charge of the Laboratory of Plant Pathology. Ill. THE FLORIDA VELVET BEAN AND ITS HISTORY. By KATHERINE STEPHENS BORT, Laboratory Aid, Forage Crop Investigations. IV. THE IMPORTANCE OF BROAD BREEDING IN CORN. 3y G. N. COLLINS, Assistant Botanist. VY. THE PRESENT STATUS OF THE CHESTNUT-BARK DISEASE. By HAVEN METCALF, Pathologist in Charge, and J. FRANKLIN COLLINS, Special Agent, Investigations in Furest Pathology. IssuED SEPTEMBER 30, 1909. ae <> WASHINGTON: GOVERNMENT PRINTING OFFICE. 1909, ko BUREAU OF PLANT INDUSTRY. Chicf of Bureau, BEVERLY T. GALLOWAY. Assistant Chief of Bureau, ALBERT F. WOODS. Editor, J. E. ROCKWELL. Chief Clerk, JAMES KI. JONES. Withdrawn FEB7 40 CONFPENTS.° Page The relation of nicotine to the quality of tobacco -............22222222.222-- 5 Variation in the nicotine content of tobacco...............-...-.--22--- 5 Relation of total nicotine content to the quality of tobacco ------ pase ne 6 Dutewent fosmis Gr micotine in tobacco... ..- ....-..-.......-...-.-.<-..- é Effects of fermentation and aging on the different forms of nicotine in Sokmeco ~~ 5.2. =<. ek ll a Ret e822 28S Oe as a ae ee ee 9 Effects of organic acids on the nicotine content of tobacco. .........--.-. 11 Eo es CS 13 Sy wat Py Se ES Ee ae ee 16 ae ae ee Se ee ee A ee 17 ee ee ee he eo een 5 oo ee SILL 17 The continued prevalence of the disease ---.-.----......--.----.------- 17 eee mrinarinE SaNe ADI oo 2 hc ee ne ook end 18 RIE OMe eo eee 5 or site. Sk he oe ce cece 19 Specific germ involved---..--- SERIO EG RRS tthe eect meet Sata See 20 nn Gr ememes OF LNG Pectenuim 22. 5... 2022. aon s ste ee ee ake 20 II SEE GP ee oe oa eae Pee 3 3 21 INN ea sd RS Se ee I ae Cs ain tei ee 24 min verres peal ane tLe hisiory:. 5... 2. -2-.-22-.62..5. 22.22. 25 Peery of sine Mlorida welyer, bean...-.2.-..2-.222-.-21.-25.2220-2. 25 The identity of the Florida velvet bean .--...-....-.-.-----------.--.... 28 | The importance of broad breeding in corn.-...----.--------.--------------- 33 I ES Ee Se ee en See eee eee a 33 Development of the present methods of corn breeding -.-.-----.--.----- 34 ES ga a A a 3 Confusion regarding the term uniformity ...-.--.-------.----.-.-..---- 36 Cultural tendencies toward inbreeding. ----.----..--------.---...---..- oF yg ES a) Cd ee eee 41 Continuous improvement through selection .--...-.-----------------.-- 41 Oo eh ee Ree eS a Se ee ee ee 42 The present status of the chestnut bark disease---..---- PR SE Pei eae aa 45 i OL aee Coram, BAEK Gibease = 2-1 = 22 24. =~. 4-225 -- 62. +2 .e He 45 ple te ee ae ee eee 45 ES ESS TE ee le ee a 47 oe ELA Be ge Pe pha oe 49 How the further spread of the bark disease may be limited. --- -- ae 49 By the inspection of diseased nursery stock ...--.-.-.---------- 49 By the prompt destruction of diseased trees......-------------- 50 By the treatment of diseased trees.......-.---- Kiet TS Se seme 50 Cmnciumong= 2852-2 ee et ta SL ss Oe Seg oie ae 52 eUNNRRCRNERE US OEE EEY Pome eerie ot Se a oe St ee eee So ssn 54 be SS os Re ee a eee 5d a4The five papers constituting this bulletin were issued in separate form on Sep- tember 18 and August 31, 1908, and on May 19, June 4, and August 30, 1909, respectively. | 141 . 3 LLU Seana: s: PLATES. PLATE 1. -Wallich’s platecot Mircuna Qiisae ss ae ee eee II. Leaf, cluster of flowers, and cluster of immature pods of the Florida velvet bean ...22 sito eee tee ee eee eee ie eee eee III. Mature pods and seeds of the Florida velvet bean..--..-....-...-- IV. Fig. 1.—Large chestnut trees killed by the bark disease. Fig. 2.— An orchard tree, showing recently girdled branches. Fig. 3.— Part of a diseased branch of a chestnut tree, showing typical pustules and form of spore discharge in damp weather---.------ TEXT FIGURES. Fic. 1. A cluster of mature pods of the Florida velvet bean -....-.-...-.-.--- 2. Map of the eastern portion of the United States, showing the distribu- tion o£ the chestnut barledisease tees seme aa ee eee 4 48 30 46 ~ MISCELLANEOUS PAPERS. B. P. I.—388. THE RELATION OF NICOTINE TO THE QUALITY OF TOBACCO. ~ By WicutTman W. Garner, Scientific Assistant, Tobacco Investigations. VARIATION IN THE NICOTINE CONTENT OF TOBACCO. Nicotine has long been recognized as the characteristic alkaloid of tobacco, but its function in the economy of the plant is not under- stood. It is present in the plant in the earliest stages of growth and is found alike in the roots, stalks, stems, and leaves. As the develop- ment and growth of the plant proceed the percentage of nicotine con- tained in the leaf constantly increases, reaching its maximum at maturity. On the other hand, as is well known, the maximum con- tent of protein nitrogen is found in the young green leaves which are growing rapidly. These facts seem to indicate that nicotine does not enter into the synthesis of the albuminoids from simpler forms of nitrogen, but rather that it is derived from katabolic changes in the albuminoid constituents, and thus continues to accumulate in the tissues so long as these are vitally active. The amount of nicotine contained in tobacco from different sources is subject to very wide variations, some samples containing less than 1 per cent, while others contain more than 5 per cent. The produc- tion of this alkaloid in the plant is influenced by a large number of factors, the relative importance of which has not been determined. No reliable conclusions can be drawn from a study of the nicotine con- tent of tobaccos grown in different parts of the world for the reason that we are always dealing with a complex group of factors and the effect of any single factor can be determined only by experiments so planned and conducted as to exclude, or at least to control, the effects of all others. In a very general way, however, it can be said that very rich heavy soils and excessive quantities of nitrogenous fertil- izers, which tend to produce a coarse, rank growth, produce a high percentage of nicotine. This relation is but a rough one and ap- plicable only to sharply contrasted differences in soils and fertilizers. The investigation of this subject carried on by the writer, though as yet incomplete, points unmistakably to the fact that in the case of any given variety of tobacco grown in a particular locality—that is, under approximately the same environment—the percentage of nicotine in different strains is roughly proportional to the albuminoid nitrogen ; but when markedly different varieties grown in different localities are compared, this relation does not hold. 5 141—1 6 MISCELLANEOUS PAPERS. From what has been said concerning the production of nicotine and its functions in the economy of the plant it might be inferred that the amount formed is controlled by external conditions of environ- ment and not by heredity, but our experiments along this line with several varieties and strains, as well as with hybrids, have shown con- clusively that there is a well-defined varietal influence distinct from external conditions, such as soil, fertilizers, temperature, moisture, and sunlight. As has been stated in a previous publication of this Department,’ there is every reason to believe that by systematic breeding it is practicable to procure strains of the important types of tobacco characterized by a high or a low nicotine content, provided the external conditions with reference to soils, fertilizers, and cul- tural methods are properly controlled. Extensive experiments with this object in view are now well under way. This work includes not only a systematic study as regards their nicotine content of large numbers of selections from different types, but also experiments in- tended to determine the relative influence on the production of nico- tine of the various factors which go to make up the environment in which the plant grows. To these should be added the effects of top- ping and suckering, practices which are now almost universal. It has already been stated that the maximum content of nicotine in the case of the leaf of the tobacco plant is attained just as the leaf reaches maturity. After this period the leaf begins to lose a part of its nicotine whether the plant is allowed to remain in the field or is harvested. Every tobacco grower is familiar with the sharp, pun- gent odor so noticeable in the curing shed and in the fermentation room, and this odor is due primarily to the nicotine which is escaping from the tobacco. From the time the tobacco is hung in the curing shed it continues to lose nicotine throughout the curing, fermentation, and aging processes. The writer has found that well fermented sam- ples of cigar tobacco are still slowly losing their nicotine after being kept.in tightly stoppered bottles for more than two years. The cause of this continued loss of nicotine will be discussed later. RELATION OF TOTAL NICOTINE CONTENT TO THE QUALITY OF TOBACCO. Although nicotine is the active principle of tobacco its production in large quantities is not desirable. On the contrary, the finest grades of tobacco contain only moderate (and even relatively small) amounts of this principle. It has long been recognized that the aroma is not governed by the amount of nicotine in the leaf, but some investi- gators have suggested that this important quality is due to its decom- 4Bureau of Plant Industry Bulletin No. 102, Part VII. ‘“A New Method for the Determination of Nicotine in Tobacco.” 1907. 141—1 RELATION OF NICOTINE TO QUALITY OF TOBACCO. 7 position products formed during the fermentation process. No direct evidence has been furnished in support of this view, and sev- eral facts point to the contrary. But even if this view be correct it does not follow that a high nicotine content is desirable, for in the matter of aroma we have to do with quality rather than with quantity. As regards the so-called “ strength ” of tobacco, the case is some- what different. This term is frequently used to designate the degree of physiological reaction of the system to the use of the tobacco in ques- tion, and when thus restricted the “ strength ” of a sample of tobacco depends on the amount of nicotine present. But this term is also fre- quently applied to the more direct effect of the tobacco or its smoke on the mucous membrane of the throat and nose. For example, when a high-grade Havana cigar is smoked it proves extremely satisfying to the smoker. and produces a marked physiological reaction, while the smoke exerts only a remarkably bland effect on the mucous mem- brane. On the other hand, some of our domestic cigar-filler tobaccos when smoked are not only less satisfying in their narcotic effects, but the smoke has a marked pungency and is irritating and biting to the nose and throat. These tobaccos are almost invariably classed as strong as compared with the Havana, whereas they actually contain less nicotine than the latter. Of course, these same differences may also be noted in different samples of the various domestic types. A long series of comparative tests conducted by the Bureau of Plant Industry has failed to establish any direct relation between the nico- tine content and the strength of the various samples of domestic filler tobaccos as judged and classified by a number of habitual smokers. In any event it seems best to consider the term “strength” as a composite one, made up essentially of two factors. The true physio- logical action which constitutes the satisfying effects to the consumer so strikingly exemplified in the Havana tobacco is commonly spoken of ‘as “ fullness ” of the smoke, while the relative freedom from the pungent, biting quality is designated by the term “ smoothness.” Thus, the Havana cigar tobaccos owe their great popularity among discriminating smokers largely to the marked fullness and smoothness of the smoke, while nearly all of our domestic filler tobaccos possessing sufficient fullness are characterized by a more or less well-defined roughness or harshness. Fullness and smoothness are generally, but not necessarily, opposed qualities of tobacco smoke. DIFFERENT FORMS OF NICOTINE IN TOBACCO. It has often been found in attempts to grow cigar-filler tobaccos in this country from Cuban seed and under conditions of soil and climate resembling those of Cuba that although of excellent quality 141—1 8 MISCELLANEOUS PAPERS. in other respects the smoke possesses the peculiar pungency or harsh- ness just mentioned. This defect is partially and sometimes efficiently remedied by resweating, followed by a long aging process. In some cases this resort fails and it is necessary to blend the tobacco with some very mild type before it can be used to advantage in the manufacture of cigars. This sharp, biting quality has often been attributed to the presence of an ethereal oil, but such a substance has never been isolated from cured tobacco. In the course of our experiments with a sample of domestic filler tobacco possessing the above-mentioned objectionable character to a marked degree, it was found that this quality was entirely lost after the tobacco had been extracted with petroleum ether. After evap- orating off the petroleum ether from the extract the residue upon warming gave off fumes which were extremely pungent and irrita- ting to the nose and throat. Upon examination these fumes were found to consist essentially of nicotine vapors. The nicotine is readily isolated from the extract by agitating the solution in petro- leum ether with water containing sulphuric acid. The aqueous layer containing the nicotine is well washed with petroleum ether and after adding an excess of alkali to free the nicotine from the sulphuric acid is once more extracted with petroleum ether of very low boiling point or with ordinary ethyl ether. After evaporation of the ether from this extract the nicotine is left as a residue in almost pure condition. This residue retains all the pungency of the original ex- tract, while the latter after removal of the nicotine no longer pos- sesses this property. A large sample of nicotine was purified by converting it into the citrate in aqueous solution and repeatedly extracting this solution with ether. The nicotine was then liberated with an excess of alkali, extracted from the aqueous layer with ether, and the ether solution dried. After evaporating the ether the nicotine was twice distilled in a current of hydrogen. The odor of this product was identical with that obtained by extracting the tobacco with petroleum ether, as already described. Although the peculiar sharpness or pungency of the smoke from tobacco of the kind in question is removed by ex- tracting the tobacco with petroleum ether, and this quality is due to nicotine, all of the nicotine is not by any means removed in this treat- ment. Kisshng has studied the relative amounts of nicotine salts removed from samples of tobacco from several different sources by extraction with petroleum ether, with ordinary ether, and with alcohol. A cer- tain definite portion of the nicotine, usually much less than half, is readily removed by extraction with petroleum ether, while further treatment with this solvent removes only traces of the remaining nicotine. It is perfectly clear, then, that nicotine is present in £41-—1 et FOI RELATION OF NICOTINE TO QUALITY OF TOBACCO. g tobacco in at least two forms, one of which is soluble in petroleum ether while the other is practically insoluble. Tobacco normally contains relatively large quantities of malic and citric acids, from 5 to 10 per cent, a portion of which is in combination with potash or lime and is of great importance in con- nection with the burning qualities of the leaf. Of these acids the portion above that required for combining with the lime and potash is doubtless largely combined with nicotine. Nicotine, though quite volatile in the free state, is strongly basic and forms comparatively stable salts with acids which are not readily volatile. The nicotine salts of the difficultly volatile polybasic or- ganic acids, such as malic, succinic, citric, and oxalic acids, are prac- tically insoluble in petroleum ether; and, hence, the nicotine in com- bination with these acids would not be removed by extraction with this solvent. There seems to be no reason for supposing that freshly cured tobacco contains any of the volatile fatty acids, such as acetic and butyric acids, but it is well known that these acids are formed in the fermentation process from the malic and citric acids, or pos- sibly more directly from succinic acid, which is itself formed by the fermentation of the citric and malic acids. Acetic acid, like nicotine, is easily volatile, and so nicotine acetate is also readily volatile. Moreover, this salt is readily soluble in petroleum ether. Ammonia is likewise a product of the fermentation of tobacco, and the small quantity of acetic acid formed in the fermentation of tobacco and which escapes volatilization is to be found in combina- tion with either ammonia or nicotine. Practically all tobaccos appear to contain more nicotine than is required for neutralizing all of the stronger organic acids which are not already in combination with mineral or inorganic bases. In other words, it appears that a portion of the nicotine contained in tobacco is present in practically a free state. It possibly does not exist in an absolutely free condition, but rather in loose combination with very weak acids of the order of tannic acid or those derived more directly from the splitting of the chlorophyll constituents. Such unstable salts would act in most respects like the free base. At any rate, the greater portion of the nicotine removed from tobacco by extraction with petroleum ether can be titrated with sulphuric acid directly, the same as if it were in the free state. EFFECTS OF FERMENTATION AND AGING ON THE DiFFERENT FORMS OF NICOTINE IN TOBACCO. It has long been known that there is a decided loss of nicotine in the fermentation process, and the amount varies from 10 to 15 per cent in the case of wrapper-leaf tobaccos to as much as a third of the total nicotine content in filler types. Different opinions have been 7034—Bul. 141—09——2 10 MISCELLANEOUS PAPERS. advanced as to whether these losses are due principally to simple volatilization of the nicotine or to its decomposition. Those who have had experience in the packing house where the fermentation is carried on do not need to be reminded of the sharp, disagreeable, and often nauseating odor emitted from the fermenting bulks, and this characteristic odor is due principally to the volatilization of the nico- tine. This volatilization of the nicotine is not confined to the fer- mentation, but is marked throughout both the air-curing and the flue-curing processes. Now it can be very readily demonstrated that there is practically no volatilization of nicotine when combined with malic or citric acids even at the highest temperatures reached in the fermentation bulks or in the curing barn in the flue-curing process. Of course this statement would not apply to the portion of these salts in which the acid constituents undergo fermentation, forming volatile fatty acids. Since the nicotine salts of malic and citric acids are insoluble in petroleum ether, it is very instructive to compare the amounts of nicotine removed by extraction with this solvent before and after fermentation. The following table shows the percentage of nicotine soluble in petroleum ether before and after fermentation, as well as the loss of this base in the fermentation process, in the case of a sample of Connecticut shade-grown wrapper-leaf tobacco: TABLE I.—Nicotine soluble in petroleum ether in a sample of Connecticut wrapper-leaf tobacco before and after fermentation. Per cent. Total nicotine before fermeniawWones ae eer Total. nicotine: aEter > Keri e mba ts 0 Tees eee ee eee ep Loss of nicotine in the fermentation process______--__-_-____ 0. 50 Nicotine soluble in petroleum ether before fermentation_____ 1. 60 Nicotine soluble in petroleum ether after fermentation_______ LeOm PTE reme se a5 2 ee a sae pe ae Re 0. 59 It will be seen that the total loss of nicotine in fermentation cor- responds very closely to the difference between the amounts soluble in petroleum ether before and after the fermentation, and it is highly probable that nearly all of this loss is due to simple volatilization. As is to be expected, the loss of nicotine is greatest in those cases in which the temperatures of the fermenting bulks reach the highest points. This volatilization of nicotine which takes place during the curing, and especially in the fermentation process, continues through- out the subsequent aging of the tobacco, but of course at a diminished rate. It is easy to understand, therefore, the marked improvement brought about by resweating or a long period of aging in the case of those types of tobacco containing excessive quantities of nicotine in an easily volatile form, which imparts a very undesirable sharpness or pungency to the smoke. 141—1 RELATION OF NICOTINE TO QUALITY OF TOBACCO. 11 In addition to these marked losses of nicotine by simple volatiliza- tion, there is a further decrease brought about by a process of oxida- tion. This latter transformation is a very slow one, and while it plays a part in the production of the brown color of tobacco it is not of importance as regards the total nicotine content. The slow oxidation of the nicotine to thick, brown-colored, tarry substances begins in the curing shed and is a continuous process thereafter, af- fecting alike the difficultly volatile and the easily volatile forms. EFFECTS OF ORGANIC ACIDS ON THE NICOTINE CONTENT OF TOBACCO. It has already been pointed out that, while the true physiological effect produced by the smoke of a given sample of tobacco depends essentially on the total nicotine content, one important factor pertain- ing to the strength of the tobacco as this term is generally under- stood—i. e., the sharpness of the smoke—i is the amount of the nicotine present which acts as if it were in the free state in that it is readily volatile. Furthermore, it has been shown that this easily volatile form of the nicotine is readily soluble in petroleum ether, while the nicotine which is in combination with malic and citric acids is not soluble. It follows, therefore, that the sharpness shown by the smoke of any tobacco should be removed either by extracting the tobacco with petroleum ether or, equally as well, by adding a sufhi- cient quantity of malic or citric acid to combine with all the nicotine present. We have made a number of experiments along this line with a sample of domestic filler tobacco which was especially well adapted for this purpose, and the results appear to justify fully the above: conclusions. This tobacco was of excellent quality in nearly every respect except that the smoke was extremely sharp and pungent, so that it was necessary to blend the tobacco with some other very mild type before using it for the manufacture of cigars. This filler was classed as a strong, very heavy type, although the total nicotine content was only 2.20 per cent, while many of our domestic filler types contain as much as 5 per cent of nicotine, The amount of this nicotine soluble in petroleum ether was determined. To a portion of the tobacco about 2 per cent of citric acid was added in aqueous solution by spraying, after which the sample was cased down for two days to allow the citric acid to diffuse through the leaf as far as possible. The nicotine in this sample before and after extraction with petroleum ether was then determined. For comparison, a sam- ple of imported Cuban filler known as “ Santa Clara,” which is a very mild type and which showed only a slight sharpness in the smoke, was also tested as to the amount of nicotine soluble in petro- _leum ether. 141—1 12 MISCELLANEOUS PAPERS. The results of these tests are shown in the following table: TABLE II.—Nicotine soluble in petroleum ether in domestic filler tobacco before and after the addition of citric acid. Domestic Domestic |filler tobac- prioeas Nicotine content. lertoe Gol with sen CO, -4 |\Santa Clara bacco. nee At tobacco. ° Per cent. Per cent. Per cent. Rotalimicotime .. Voss. csc ee ee ee ee Ce Eee eee 2.20 Dealt 1.33 Nicotine insoluble im petroleum ether == a= =e —ee = seer eee 0. 76 1.66 0.79 ‘OH Tee”? SINT CO DIME! = cites e a ahs tae a Ces a rs eV 1.44 | 0.47 0.54 It will be observed that two-thirds of the total nicotine contained in the domestic filler tobacco is in the easily volatile form which exists either in the free state or loosely combined with weak acids and that the addition of citric acid renders the greater portion of this insoluble in petroleum ether. The fact that the nicotine is not made wholly in- soluble by the addition of the acid is accounted for partly by reason of the shght solubility of the nicotine citrate in petroleum ether, but mainly because the solution of citric acid added had not diffused throughout the leaf tissue. Better results could be obtained by add- ing the citric acid solution before the fermentation process is com- pleted, thereby affording a better opportunity for the even diffusion of the acid through the leaf. Even under these unfavorable condi- tions the soluble portion of the nicotine was reduced below that of the mild Santa Clara sample. Samples of this tobacco to which the citric acid had been added were made into cigars which were tested by a number of persons, and the universal opinion has been that the sharpness or pungency of the smoke has been almost entirely removed by this treatment. Other similar acids, such as malic and tartaric acids, are also efficient in overcoming this property of the smoke, but oxalic acid does not give satisfactory results. The easily volatile fatty acids, such as acetic acid, form easily volatile salts with nicotine and hence do not produce any decided influence in this respect. It has already been stated, moreover, that these salts are soluble in petroleum ether. Citric and malic, succinic, and finally acetic and butyric acids merely represent intermediate stages in the degradation by fermenta- tive processes of the sugars to carbon dioxid and water. Citric and malic acids exist in the leaf prior to the fermentation, and whether the quantity of these is diminished in this process depends in any given case on whether the loss occasioned by partial transformation of these into succinic, butyric, and acetic acids is made good by the formation of further quantities by fermentation of the sugars. Acetic acid is formed during the fermentation at the expense of the citric 141—1 | RELATION OF NICOTINE TO QUALITY OF TOBACCO. 18 and malic acids, and hence it follows that prolonged fermentation can never entirely remove the pungency of tobacco smoke due to the easily volatile nicotine. In the presence of an excess of citric acid, however, the greater portion of the acetic acid would be expelled because of its easy volatility. Citric acid is a normal and valuable constituent of tobacco, and its addition in moderate amounts could not therefore injure the quality of the tobacco in any way. There is every reason to believe that its addition during the fermentation process would prove highly bene- ficial to those types of cigar-filler tobacco which contain excessive quantities of nicotine not already in combination with citric or malic acids. This could probably be best applied by spraying the tobacco at the time of turning the bulks with an aqueous solution of such con- centration as to add from 1 to 2 per cent of the acid. COMPOSITION OF TOBACCO SMOKE. Now that we have seen that organic acids like citric, malic, or tartaric acid are efficient agents in preventing the nicotine contained in the tobacco from imparting an undesirable sharpness to the smoke, the question naturally arises as to the manner in which these acids effect this result. There would seem to be three possible ways in which this effect might be produced: (1) The nicotine salts of these acids are so difficultly volatile that the nicotine 1s decomposed in situ by the heat from the burning end of the cigar; (2) these salts, on account of their slight volatility at lower temperatures, are condensed from the smoke before it enters the mouth of the smoker and thus constantly accumulate in the unburned portion of the cigar; and (3) the nicotine passes into the smoke and enters the mouth of the smoker in the form of the salt instead of in the free state, thus losing its pungency or biting qualities. Which of these alternatives affords the true explanation can best be answered by smoking the tobacco in a suitable apparatus and determining the amount of the nicotine contained in the smoke and that remaining in the unsmoked ends of the cigars. A number of investigators have endeavored to study the composi- tion of tobacco smoke, but the problem presents many difficulties in the matter of securing satisfactory analyses. Without attempting to enter into this subject fully, it may be said in brief that the smoke is, in the first place, mixed with large amounts of nitrogen and small quantities of oxygen derived from. the air used in the combustion. In addition to these, the smoke proper contains, as difficultly condens- ible gases, small but appreciable quantities of carbon monoxid, hydro- eyanic acid, and probably also hydrogen sulphid. These latter are three well-known poisonous gases, although the quantities contained in tobacco smoke are probably too small to be of any special signifi- 141—1 14 MISCELLANEOUS PAPERS. cance. Among the more easily condensible constituents may be men- tioned nicotine and its decomposition products, especially pyridin, an ethereal oil of fragrant odor and a complex mixture of thick, tarry substances. Of course the smoke also contains large quantities of carbon dioxid and water vapor resulting from the combustion of the tobacco. The nicotine content of tobacco smoke has been extensively studied by Kissling,’ whose principal conclusions may be briefly sum- marized as follows: Considerably less than half of the total quantity of nicotine is ordinarily destroyed in the smoking of a cigar, and greater or lesser quantities enter into the smoke, depending on what portion of the cigar remains unsmoked. In the case of a lot of cigars containing 3.75 per cent of nicotine, when two-thirds of the entire cigar were smoked about 28 per cent of the nicotine in the smoked part of the cigar was contained in the smoke; about 12 per cent had accumulated in the unburned portion of the cigar, and about 60 per cent was destroyed. In another experiment in which nearly seven- eighths of the entire cigar. were smoked, the percentages were 52, 5.5, and 42.5, respectively. Unfortunately, in these tests the cigars were smoked by drawing through them a constant flow of air instead of by intermittent “ puffs,” as in the actual practice of smoking, so that the above values are not entirely applicable. Kissling con- siders that the physiological effects of tobacco smoke are produced almost wholly by nicotine and its immediate decomposition products of the pyridin class of compounds. We have carried out several experiments along the lines of those conducted by Kisshng to determine more particularly the effects produced by citric acid on the nicotine content of tobacco smoke. A portion of the sample of tobacco repeatedly referred to in this paper was sprayed with an aqueous solution of citric acid in the manner already described, and was then made into cigars. Another portion. of the same sample without the addition of the acid was also made into cigars. A lke number of each was smoked in a suitable ap- paratus, the smoke being drawn through a series of flasks containing sulphuric acid to absorb the nicotine. The wash waters containing the nicotine from the smoke were then distilled in a current of steam to remove any indifferent volatile matter, an excess of alkali added, and the mixture was then again distilled. The distillate containing the nicotine mixed with pyridin and a relatively large amount of ammonia was accurately neutralized with sulphuric acid and then evaporated to dryness. The nicotine and pyridin were then separated from the ammonia by extracting the residue with small volumes of absolute aleohol. The apparatus used for smoking the cigars was so ¢Dingl. Polyt. Journal, 1882, p. 64. ’ The word ‘ puff” in this paper is used to cover both the inhalation ard ex- pulsion of the smoke. 141—1 7 \ RELATION OF NICOTINE TO QUALITY OF TOBACCO. 15 constructed that the air could be drawn through the cigars either in an uninterrupted current or intermittently, and the rate of smoking was so regulated that about thirty minutes would be required for the complete combustion of a cigar. In one series of experiments ap- proximately two-thirds of each cigar were smoked, while in a second series only one-half of each was consumed. The results obtained are recorded in Table III, but it is to be understood that the values shown are only approximate, since they are influenced by a multitude of factors which can not be rigidly controlled. In experiments 1 and 3 the cigars were smoked by intermittent “ puffs,’ while in ex- periments 2 and 4 they were smoked by a constant current of air. In every case the results given in the columns designated by “A ” refer to cigars made of tobacco to which citric acid had been added, while those under columns headed “B” refer to cigars from the natural leaf. All results are expressed in percentages and are the averages obtained from smoking a number of cigars. The cigars used contained 2.2 per cent of nicotine. The percentages of nicotine given in the table are all calculated to the amount of nicotine in the portion of the cigar actually smoked, and not to that contained in the whole cigar. The values for nicotine include at least a portion of the pyridin formed by the partial decomposition of the nicotine, in- asmuch as no method has been devised for the quantitative separation of these two substances. TABLE III.—Nicotine in the smoke of cigars made from tobacco to which citric acid had been added and those made from natural leaf. Experiment 1.| Experiment 2. | Experiment 38. | Experiment 4. A. | B. A (eB. | a. Bee Portion of total weight of cigars | Perct.| Perct.| Perct.| Perct.| Perct.| Perct.| Perct.| Per ct. TE SEs ee ee a eee ee Te 70 | 60 63 49 50 48 | 51 Nicotine of smoked tobacco found i OR ae. ee 25.5 34.5 | 27 RS Beret ee ieee 22 | 26.3 Nicotine-of smoked tobacco recoy- : ered from residual ends.......... 14 8 4 42 29 18 48 40 Nicotine destroyed in process of smoking or expelled directly into the air from the burning end of : | DEE ee A og ON Eee 60.5 57.5 19 ite Pre re eo) ase: Ss Se 30 33.7 It will be seen that when about two-thirds of a cigar are smoked about 30 per cent of the nicotine of the smoked portion passes into the smoke, while from 10 to 20 per cent collects in the unsmoked por- tion, and the remainder is either destroyed or escapes into the air. The striking increase in the amount of nicotine which collects in the unsmoked portion of the cigar when it is smoked by means of a con- stant current of air instead of by intermittent “ puffs ” is due to the circumstance that in the first case practically all of the nicotine is drawn into, or through, the unburned portion of the cigar, while in the latter case a large portion of the nicotine escapes into the air 141—1 16 | MISCZLLANEOUS PAPERS. during the intervals between “ puffs.” The relative amount of nico- tine which is to be found in the smoke depends chiefly on the relative length of the unsmoked portion of the cigar and on the rate at which the smoke is drawn through the cigar. eas The point of chief interest, however, is the effect of the citric acid on the nicotine content of the smoke. It 1s apparent that in every case the quantity of nicotine in the smoke is reduced, while that which collects in the residual end of the cigar is correspondingly increased. This difference, nevertheless, is too small to account for the marked effect produced on the quality of the smoke. Apparently the only possible explanation of this pronounced effect on the sharp- ness of the smoke is that in the presence of the citric acid the nico- tine enters the smoke in the form of a salt rather than in the free state, and thereby loses its pungency while still exerting the usual physiological effect. CONCLUSIONS. Tt has been shown in the preceding pages that there is no direct relation between the so-called “strength” of tobacco when used for smoking purposes and the total content of nicotine. However, a distinction must be drawn between two forms of nicotine con- tained in tobacco, one of which is easily volatile and readily soluble in petroleum ether while the other is volatile only at elevated tem- peratures and is almost insoluble in petroleum ether. The unde- sirable sharpness or pungency contained in the smoke from certain types of cigar-filler tobacco and which constitutes one of the two factors included in the term “ strength” as applied to the smoke is due almost entirely to the volatile, easily soluble form of nicotine which acts as if it were in the free state. On the other hand, the true physiological effects of the smoke, as embodied in the term “ full- ness,” are proportional to the total quantity of nicotine. The pungent, harsh quality of the smoke is partially, but not en- tirely, removed by protracted resweating and aging of the tobacco, whereby the easily volatile nicotine is largely expelled. This unde- sirable property is entirely removed by extracting the tobacco with petroleum ether, which simply dissolves out the volatile nicotine. Finally, the addition of sufficient citric acid-to the tobacco to com- bine with all of this easily volatile nicotine efficiently overcomes the sharpness or pungency of the smoke. It can best be added by spray- ing the tobacco with an aqueous solution when the fermenting bulks are being turned. The addition of the citric acid reduces somewhat the amount of nicotine in the smoke of the cigar, but not enough to account for the marked effect on the quality of the smoke. It is suggested, therefore, that probably the nicotine enters the smoke in the form of a salt rather than in the free state, thereby losing its pungency. 141—1 B. P. I.— 399. THE GRANVILLE TOBACCO WILT. By Erwin F. Situ, Pathologist in Charge of the Laboratory of Plant Pathology. HISTORY. Attention was first called to the Granville tobacco wilt in Septem- ber, 1903, by McKenney, then connected with this Department. He attributed it to a fungus (Fusarium) nearly related to those studied by the writer on cotton, melon, and cowpea. No proofs from inocu- lation were obtained by McKenney. A few days after the appearance of McKenney’s paper a bulletin was published by Stevens and Sackett, of the North Carolina Agri- cultural Experiment Station, describing this disease and attributing it to bacteria. Their diagnosis also depended solely on field observa- tions and microscopic studies, but this part of the work was well done. In 1905, as the result of personal examinations of infected plants, studies of the microorganism in pure cultures, and successful inocu- lations therefrom, the writer confirmed the findings of Stevens and Sackett as to the bacterial nature of this disease. Numerous success- ful infections of tobacco were obtained both by needle puncture from pure culture and by plantings in infected soil. The organism was identified provisionally as closely related to Bac- terium solanacearum, a species described by the writer in 1896 as the cause of a widespread and destructive brown rot of the potato, tomato, and eggplant. This conclusion was based on the similar behavior of the tobacco bacterium and of undoubted Bacterium solanacearum (derived from tomato and potato) in a variety of culture media. The shade of doubt remaining in my mind at that time was due to the fact that many cross-inoculations (potato to tobacco and tobacco to to- mato), while showing multiplication of bacteria in the inoculated tissues and some other signs of disease (brown stain in the bundles, and on tomato stems the development of incipient aerial roots), did not contract the wilt. THE CONTINUED PREVALENCE OF THE DISEASE. Both in North Carolina and in Florida this wilt of tobaceo has con- tinued with increasing severity, the losses in 1908 being greater than those of any previous year. In North Carolina quite a number of 7034—Bul. 141—09 3 17 » 18 MISCELLANEOUS PAPERS. planters have lost whole fields and others considerable parts of fields. Still others have harvested their tobacco green to save some part of it. The entire loss in 1908 in North Carolina is not known, but is esti- mated at upward of $100,000. In Florida the disease has also made great inroads in several places, causing serious losses for three or four years. In 1908, one man lost 20 acres of tobacco under shade by reason of it. The same year a company lost nearly every plant on 12 acres of home-grown Sumatra under shade and also a considerable part of 95 acres of imported Sumatra, also grown under cover (cloth). On many of these fields tobacco has followed tobacco for a long series of years (eighteen years in one field). The worst feature of this disease is the fact that fields once infected remain infected indefinitely, or at least for many years, and are also use- less for growing any other plant of this family, e. g., potatoes, tomatoes, eggplants, or peppers. The disease is therefore a very serious one. If it continues at its present rate of progress, tobacco growing in the infected districts will become impossible within a few years, and if it should extend to all the tobacco-growing sections of the United States this industry would be destroyed. It is therefore of the utmost im- portance to keep it out of sections which are still free from it. To this end correct information respecting its nature should be disseminated as widely as possible. An ounce of prevention is worth tons of cure— and, moreover, @ cure is not in sight. Something may be done, how- ever, by good field hygiene to restrict its progress. BACTERIAL ORIGIN OF THE DISEASE. The writer no longer has any doubt as to the bacterial origin of this disease. On two or three occasions he has found Fusarium on tobacco stems affected by this disease, but not commonly, nor ever exclusively. Generally there were also a great many bacteria present in the stems occupied by the fungus. Once I have observed Fusarium to be a secondary infection—in one plant out of many inoculated with the bacterium some years ago. Almost all of the diseased tobacco plants examined by me from North Carolina and from Florida, a hundred or more, in several differ- ent years, were attacked by bacteria to the exclusion of fungi. Fusa- rium certainly was not present. Nothing here said, however, need be construed as a denial of the occurrence in this country of a Fusarium disease of tobacco, since it 1s very reasonable to suppose the existence of such a disease. There are many such diseases, as the writer was the first to point out. One occurs on the tomato and another on the potato. Why not one on tobacco? The evidence necessary to estab- lish such a contention, however, is yet to be procured. Meanwhile we may consider the Granville wilt as solely bacterial in its origin. 141—II THE GRANVILLE TOBACCO WILT. 19 NEW EXPERIMENTS. ‘Experiments by the writer in the summer of 1908 have demonstrated that the Carolina tobacco disease is readily communicated to tomatoes through the root system. These infections were obtained by trans- planting healthy tomatoes into a bed of good hothouse soil in which tobacco plants affected by the Granville wilt had been buried recently. The stems of these tobacco plants, which were obtained from North Carolina, were swarming with the bacteria peculiar to this disease. The tomato plants were infected through broken roots, the plants being of considerable size when set into the infected bed. The experiment was begun at the end of July, and up to this date (August 18) nineteen tomato plants have contracted the disease. This disease is typical tomato wilt, the vascular bundles of stems and mid- ribs being browned and their vessels filled with the grayish white bacterial slime peculiar to the genuine tomato disease. Dissections showed the brown stain and the bacteria in the bundles to be more abundant as one passed from the top of the plant toward the roots, and always one or more broken roots were found diseased to the very end, i. e., browned and occupied by the bacteria. Most of the roots, how- ever, as well as all of the underground stem and all of the parts above ground, were free from external appearance of disease other than the wilt, i.e., from wounds, spots, or stains. The wilting was sudden,1.e., not preceded by any yellowing of the foliage. Numerous incipient roots developed on the stems. No other tomato plants in the houses or on the grounds (several hundred) showed any signs of this disease. The Jimson weed (Datura stramonium) planted in this bed also contracted this disease through the root system. Moreover, with bacterial slime taken from the interior of four of these wilting tomato plants (upper part of the stem) I have caused the Granville tobacco wilt inside of two weeks on four large healthy tobacco plants, the bacteria being introduced into leaves and stems by means of needle pricks, and also by pulling off leaves and rubbing the scars with the crushed tomato stems. The signs of this tobacco disease so obtained were in every way characteristic—wilt of follage, darkening of the veins of the leaves, longitudinal dark stripes on the stem origi- nating from internal staining, brown stain of the vascular bundles of the stem and leaves, and vessels gorged with the characteristic bacteria. Some of the uninoculated leaves also dried out irregularly, and the apical leaves on the inoculated side of the stem became dwarfed and distorted. The inoculations were made in another hothouse (where no other Solanaceae were grown), the checks remained healthy, and when the wilting plants were cut for examination the root system in three of the four plants was still free from disease, the inoculations having been made at the top of the plants. Moreover, in all cases (four places on each plant) the disease began in the pricked and rubbed areas. 141—11 20 MISCELLANEOUS PAPERS. SPECIFIC GERM INVOLVED. The cultural characters of the tobacco organism are the same as those of Bacterium solanacearum derived from tomato or potato, and now that good cross-infections have been obtained no doubt remains that the Granville wilt of tobacco and the brown-rot ef potato, tomato, and eggplant are one and the same disease, i. e., due to the same organism, all of these plants belonging to the nightshade family and being rather close relatives. The Florida tobacco wilt at Quincy and Hinson appears to be the same thing. I examined diseased plants from Florida some years ago and again this year. The writer formerly stated (1896) that he did not succeed in cross- inoculating Bacterium solanacearum into tobacco and peppers, and at that time he believed tobacco to be exempt, but not many experiments were made, and we may assume either that the cultures used had lost their virulence or that the particular plants selected were too old or growing too slowly, or for some other reason were unusually resistant. The writer now believes that Bacterium solanacearum does frequently lose its virulence by continued culture; that, in general, old and slow- growing plants are difficult to infect; and that some individuals and some varieties are more resistant than others. This, I believe, suffi- ciently explains the former failures. We may conclude, therefore, in searching for remedies that we have one disease to deal with and not several. METHOD OF ENTRANCE OF THE BACTERIUM. If stomatal infections occur, which is not unlikely, especially in wet weather, they have not yet been demonstrated. So far as we know, this organism enters the plant only through wounds. Van Breda de Haan found the root system especially subject. Stevens and Sackett state that the infection is first in the root. A large number of infec- . tions undoubtedly take place under ground, the organism present in the soil entering the plant through wounds made in transplanting or cultivating, or by small animals infesting the soil. Roots broken in transplanting and leaves pulled or pinched off at that time are respon- sible for many infections, and it would seem that by care the number of such wounds inviting infection might be greatly reduced. It has been observed in Sumatra, where occurs a destructive bacte- rial wilt some years ago identified by Hunger as due to Bacterium solunacearum, that the tobacco plants are peculiarly subject to it when grown on land infested with eelworms (nematodes) or with insects which attack the roots or base of the stems. Rainy weather is favor- able to the progress of this disease, although the wilt may be detected first in dry weather. In this country it has been observed, especially by Earle on tomatoes in Alabama, that wet soil is peculiarly favorable to the spread of this disease. All observers agree that the root system 141—II THE GRANVILLE TOBACCO WILT. 21 is peculiarly lable to attack. To a very considerable extent the destructive prevalence of this disease seems to hinge on the occurrence of root-infesting nematodes. They are common in the diseased to- bacco soils of Florida and probably occur also in those of North Carolina. REMEDIES AND PALLIATIVES. (1) This organism is to be regarded as a very bad weed lable to be distributed in many ways. It is worse than ordinary weeds because it is invisible. On plantations free from the disease a rigid quarantine should be erected against plantations subject to the disease. Nothing should be received by the farmer from the latter—seeds, young plants, raw tobacco, cured tobacco, packing cases, wagons, tools, fertilizers, laborers, horses, cattle, etc., all should be excluded. Avoid also the manuring of fields with tobacco waste even when it is believed to originate from clean sources. (2) Do not plant tobacco on lands subject to this disease. Rent healthy land at a distance if necessary. To plant infected land invites disaster. Jt és not safe to do so even after several years. Stevens and Sackett have recorded several cases where the disease returned after five to eight years rest of the soil, and one instance where it did not return after a rest of fifteen years. (3) Do not cultivate any other similar plants on infected land. Tomatoes, potatoes, eggplants, peppers, and pepinos are all more or less subject to this disease, and their growth will help to continue the organisms in the soil. Grow plants of some entirely different family. Look out also for solanaceous weeds. It is not known whether these are actual harborers of the bacteria, but it is well to destroy them. In the hothouse the writer has found the plant called Stramonium, jimp- son, or Jamestown weed quite subject to this disease. The disease is also readily inoculable into the black nightshade (Solanum nigrum). (4) Search the affected tobacco fields carefully, especially toward the end of the season, in the hope of finding resistant plants from which seed may be saved for the breeding up of resistant sorts. There is some hope that this may be accomplished. The intelligent planter can serve himself in this matter as well as help to excite general in- terest in the subject. The end in view is worth the expenditure of much time and trouble. (5) If it is impossible to avoid the use of infected lands, then cer- tainly avoid planting the wettest spots, and underdrain such fields as speedily as possible. (6) Select for the seed beds soil which is uncontaminated, and trans- plant to the field early, i. e., while the plants are quite small, and with the greatest care to avoid breaking the roots. Cultivate shallow with the same thought in mind. Under no circumstances use large plants 141—I1 i a) MISCELLANEOUS PAPERS. on such lands. The roots are certain to be broken more or less in transplanting and equally certain to become infected, with subse- quent infection of the whole plant. Probably half the trouble on such lands, if they are free from nematodes, might be avoided by careful attention to this one particular. Under tents, sowing the seed in the place where the plant is to stand might also be given a trial. (7) Wound as little as possible the base of the plants and the tops by pruning or pulling away leaves. Do not jerk off leaves when setting out. It is a good rule under ordinary circumstances to balance root and top by removing a portion of the leaves at planting time, but not when this disease is present, since infection is hable to occur in this way. The same end may be accomphshed with less danger to the plants by using greater care in transplanting, and especially by trans- planting when the plants are small. Top the plants in dry weather. (8) Avoid fields known to be infected with root nematodes. They wound the roots and enable the bacteria to gain an entrance. Hunger demonstrated this on tomatoes in the Dutch East Indies. If such fields must be used, the nematodes may be reduced in number by rotation with winter grains (oats, rve, wheat) followed by velvet beans but not — by cowpeas (except Iron), since ordinary cowpeas are much subject to root nematodes and will increase the number of them in the soil. Vel- vet beans are not subject to nematodes. The number of nematodes in the soil may also be reduced by a skillful use of trap crops, but an unskillful use of the same will increase their number. The object ofa trap crop is to get as many nematodes as possible encysted in the roots, which are then pulled up and burned. Cowpeas may be used as a trap crop. They should be removed and burned as early as the fourth week, 1. e., before the nematodes have escaped again into the soil in increased numbers. It would be best, however, to put this work into the hands of persons having some knowledge of biology, since trap-cropping for nematodes is still in the experimental stage. (9) Remove and burn affected plants as soon as they are detected. They are swarming with innumerable millions of infectious particles ¢ which plowed under or allowed to fall to the ground are washed into the earth and will serve to increase the soil infection. Such plants are also a source of danger to your own free fields and to those of your neighbors. There are enough neglected tobacco plants in Granville County to infect the whole United States if properly distributed. (10) Under no circumstances throw tobacco refuse on your fields, or into your barnyard, or into streams or roadways. Such refuse is a good fertilizer, but it may also prove the carrier of this disease and the danger is too great. The organism may live in the dead stems for some time—just how long is not known. Do not take any risks. The “4 single tobacco plant may contain ten thousand million of these bacteria. 141—11 THE GRANVILLE TOBACCO WILT. os organism is not known to produce spores and is believed to be de- stroyed by a short exposure (ten minutes) to 52° C. (125° F.), but until it has been confirmed on a large scale in the field it is best to be cautious about using waste material from the curing house. Some portion of it containing these bacteria may not have been heated hot enough to destroy them. (11) Strive to keep uninfected fields free from infection. To this end look out for the tobacco refuse; also for wash of rain water from infected lands (this to be turned aside by ditches and dikes). Be watchful also for other sources of infection, e. g., dirt or fragments of infected tobacco carried on tools, feet of horses and cattle, ete. Tools may be disinfected (after removing the dirt) by a short expo- sure to live steam, boiling water, or the open flame (gasoline torch). Five minutes’ exposure ought to be ample. They may also be disin- fected by the use of germicides, e. g., 5 per cent carbolic acid (poison) or one-fifth per cent mercuric chlorid (poison). Carbolic acid or mer- curic chlorid (corrosive sublimate) are better than formalin, since the latter is volatile and likely to be under the certified strength (40 per cent formaldehyde) in broken packages or old corked bottles. Mer- curic chlorid tablets prepared for this purpose, so that weighing is not necessary, are on the market. Wooden pails and clean boiled water should be used. The germicidal action of mercuric chlorid is destroyed by contact with metal dishes. These substances should be kept out of reach of children. (12) Avoid also the increasingly common southern practice of sowing fields with dirt from other fields, the idea being to inoculate the soil with nitrogen-fixing organisms. This method of inoculating soils isa bad practice under any circumstances, 1. e., one well calculated to dis- seminate plant parasites and one particularly reprehensible in localities where this disease prevails or is liable to occur. Nematodes, injurious insects, parasitic fungi, club-root of cabbage and other crucifers, and plant-destroying bacteria, not to mention animal parasites, are all liable to be disseminated in this way. To let loose a whole menagerie for the sake of obtaining an ox or an ass is not a good policy. Obtain pure cultures for soil inoculations from the Department of Agriculture or the State agricultural experiment station. (13) Those who grow Sumatra wrapper-leaf tobacco under tents erected at great expense, and whose annual crop is worth $1,000 or - $1,500 per acre, can afford greater expenditures in combating this dis- ease than the ordinary planter. Such persons should endeavor to free the soil of this organism by fire or by steam heat. They should also combat the nematodes. Bacterium solanacearum is quite sensitive to heat, and if the whole body of the soil could be warmed up to 125° F. for fifteen minutes this organism would be destroyed. If such attempts fifteen minutes this organism would be destroyed. If such attempts are made great care must be taken that the sterilized portions are not 141—11 24 MISCELLANEOUS PAPERS. reinfected by careless workmen from the parts not yet treated. Live steam under considerable pressure conveyed through parallel lines of buried gas pipes and let loose into the soil at short distances by suit- able small openings is probably the best method of applying steam. It may be applied, however, as Shamel has recommended for seed beds, i. e., under large shallow metal pans, which are then moved to a fresh portion of the field, and so on until all is treated. ~ « a Se en a , > = = a - «fo oe i ae os: Fic. 3.—PART OF A DISEASED BRANCH OF A CHESTNUT TREE, SHOWING TYPICAL PUSTULES AND FORM OF SpoRE DISCHARGE IN DAMP WEATHER. Magnified 3 diameters. ) PRESENT STATUS OF CHESTNUT BARK DISEASE. 49 RESTRICTION OF SPREAD. HOW THE FURTHER SPREAD OF THE BARK DISEASE MAY BE LIMITED. By THE INSPECTION OF DISEASED NURSERY STOCK. It beccmes more and more evident as this disease is studied that diseased nursery stock is the most important factor in its spread to distant points. In that part of the country where it is already well established in the native chestnuts its progress is rapid and sure, but there is no evidence at present that it is able to pass to remote districts, tens or hundreds of miles away, except on diseased nursery stock. Of course it is conceivable that the spores are carried by birds. Such distribution would, however, follow in general the great lines of bird migration north and south and hence would not be an important factor in the western spread, except locally. During the summer of $908 nearly every chestnut nursery and orchard of impor- tance in the Atlantic States north of North Carolina was visited, and very few were found free from the bark disease. Several cases were observed where the disease had obviously spread from the nursery to adjacent wild trees. This is the only way in which the disease is hkely to spread beyond the Alleghenies. It is therefore obvious that every State in which the chestnut or chinquapin grows should as speedily as possible pass a law putting the chestnut bark disease on the same footing as other pernicious diseases and insect pests, such as the San Jose scale, against which quarantine measures are taken. The Department of Agriculture will be glad to give detailed suggestions or advice regarding the framing of such laws. Inspectors who already have legal power to quarantine against this disease should now take special care that no shipment of chestnut stock escapes their rigid inspection. A campaign of education should also be undertaken by patholo- gists and inspectors in every State in order to acquaint the public with the nature and appearance of the bark disease, so that it may be quickly recognized and stamped out in any particular locality in which it appears. The Department of Agriculture will cooperate in the following ways: Specimens from suspected trees sent in by any person will be promptly examined and the presence or absence of the disease reported. Typical specimens showing the disease (with the fungus previously killed by soaking in formalin to insure against any infection from this source) will be sent upon application to any inspector, forester, pathologist, or other State or experiment sta- tion officer, to any nurseryman or orchardist growing chestnuts, or to any botanist or teacher of botany. So far as the supply per- mits lantern slides and photographs will, upon application, be loaned for special lectures, exhibits, etc., to the officers of States, experiment 141—y 50 MISCELLANEOUS PAPERS. stations, or colleges. By these means the inspectors first, and then the general public, may become familiar with the appearance and work of the disease in localities that it has not yet reached, and when it does appear may be able to recognize it before it is too late to take efficient measures against it. Although its present distribution is that shown by the map (fig. 1), the bark disease may be confidently looked for in any orchard or nursery in the United States that contains chestnut trees. All such places should therefore be rigidly inspected at the earliest possible date. By THE PROMPT DESTRUCTION OF DISEASED TREES. When the bark disease is first noticed in any locality, all the affected trees should be immediately cut down, unless, as in the case of orchard and some few ornamental trees, they are of sufficient in- dividual value to warrant special treatment. Diseased trees if un- treated are doomed to death in any case. If permitted to stand, every such tree becomes a center of infection, certain to spread the disease to all neighboring trees, and so long as it will soon die if left to itself the sooner it is cut down the better. When cut, the brush should be immediately gathered and burned in order to destroy the fungus in the bark. Whenever the bark is removed from the trunk, as, for example, when the trees are to be used for poles, it should be immediately burned with the brush. Even when the tree is to be used for firewood an effort should be made to cut off at least all the diseased patches of bark on the trunk and large limbs when the tree is cut and to burn this bark along with the brush; otherwise the brush and the piled wood will continue to spread infection, since it has been found that the fungus continues alive on dead bark for at least six months after cutting. Sprouts arising from the stumps of cut trees will be free from the disease for the first year at least, but must then be carefully inspected to be sure that no infection has persisted. By THE TREATMENT OF DISEASED TREES. During the past two years the Office of Investigations in Forest Pathology has been conducting certain experiments and collecting information in regard to the best methods of treating diseased trees. At present it is impossible definitely to record general beneficial results from any of the sprayings which have been undertaken or have been under observation. This may in part be due to the fact that it is yet too early to judge satisfactorily all the results and in part, per- haps, to the infrequency of sprayings. 141—y area ee PRESENT STATUS OF CHESTNUT BARK DISEASE. 51 Observations and experiments seem to bear out the statement that it is very improbable that any method of spraying can interfere with the growth of the fungus if it has once established itself in the inner bark, but it may be of considerable importance in preventing the development of spores which come from other trees or from other parts of the same tree. It has already been demonstrated that the crotches of branches and enlarged bases of sprouts are very susceptible to infection because they are favorable places for the lodgment of water, dust, spores, ete. In a large majority of cases infections are definitely known to have originated at a point where the outer bark had been injured in some way, leaving the inner living bark exposed, or where the entire bark over a more or less limited area had been stripped from the tree or eracked and split away from the wood. Certain injuries which are known to have afforded entrance for the disease have been of such a nature that they might easily be overlooked, while others have been quite obvious, even to the careless observer. Among the latter may be mentioned broken limbs, split limbs, branches which have been carefully cut but not properly treated with tar or paint, bruises from hames, plows, and cultivators; also poor grafts and diseased grafting scions. Among the former may be included bruises from boot heels, climbing spurs, holes made by borers and other insects, knife and saw cuts, and frost cracks, Almost the only treatment that can at present be safely recom- mended as surely retarding the spread of the disease to a greater or ‘less extent is one which will never be of practical use except in the case of orchard trees or certain valuable ornamental trees. It consists essentially in cutting out the infected branches or areas of bark and carefully protecting the cut surfaces from outside infection by means of a coat of paint or tar. This cutting must be thoroughly done and the bark of every infected place entirely removed for a distance of at least an inch (where the size of the branch permits) beyond the characteristic, often fan-shaped, discolored areas produced by the growing fungus in the inner bark. All small infected twigs or branches should be cut from the tree, the cut being made well back of the diseased area. A pruning knife with an incurved tip, a hollow gouge, or any other clean-cutting instrument will serve for cutting out diseased spots. So far as the exigencies of the case will permit, all borers’ holes should be cut out. It has been repeatedly observed in the field that infection often starts where borers are at work, or even at the old holes made by them. The paint or tar may be applied by means of a good-sized brush, care being taken to cover every part of the cutting. Treatment should begin, or observations at least, at the base of the tree and the fact ascertained whether the disease has 141—y 52 MISCELLANEOUS PAPERS. already girdled the trunk. If such is the case it will be a waste of time to attempt any treatment; instead, cut the tree down at once. A rigid watch must be kept, especially during the growing season, for new infections or infections which were overlooked in the earher ex- aminations, and if any are observed they must be treated promptly, as above mentioned. Constant vigilance is necessary to keep the disease in check. It is suggested that examinations be made about June 1, July 15, and September 1. During a very rainy or foggy season, when conditions are particularly favorable for the growth of fungi, it may be advisable to inspect as often as once a month. In regions in which the disease is so widespread that almost every tree is infected, as, for instance, within 25 miles of the city of New York, it is extremely doubtful whether any individual treatment. will pay. Under such conditions immediate reinfection is almost sure to occur at one or more of the small unnoticed abrasions or injuries which are quite certain to exist on most trees. In a region, however, where only isolated cases have yet appeared it is quite possible to stamp out the disease, or at least to prevent its rapid spread, by promptly cutting out and carefully burning all diseased bark and limbs, thus destroying these new sources of infection. If a tree is too badly infected to be worth treating it should not be left standing, for it will then become a continual menace to all surrounding chest- nuts. The Office of Investigations in Forest Pathology asks the cooper- ation of all persons who have observed the disease or experimented with it in any way. If such people will send in an early report of the: kind of treatment used, time of treatment, methods employed, and results obtained (even if adverse), it may be possible to arrive at an earlier and more definite conclusion in regard to the possibilities or impossibilities of control than would otherwise be the case. CONCLUSIONS. It is to be hoped that in the economy of nature some limiting fac- tor will arise to check the spread of the bark disease before it has wrought the same destruction throughout the country that it already has in the vicinity of New York. But at present there is nothing in sight that promises even remotely to check its spread into new ter- ritory except the general adoption of the measures advocated in these pages. It can not be argued that because of its apparently recent origin and rapid spread it will soon disappear of itself. Such dis-— eases as pear-bliight and peach yellows have been in the country for more than a century and yet show no sign of abating except when actively combated by modern quarantine methods. Nor can any conclusions be drawn from the fact that chestnuts in the Southern 141—- PRESENT STATUS OF CHESTNUT BARK DISEASE. 53 States have suffered from a disease during the past twenty years, since, as already stated, that is a totally different thing from the bark disease. Where the bark disease is already firmly established and has at- tacked 50 per cent or more of the chestnut trees, as in the vicinity of the city of New York, it is probably too late to try to do anything, but where the disease is just appearing there is no reason to doubt that strict quarantine methods will apply as well to this as to any other disease, whether of plants or animals. The question to settle is simply which is more costly—to use the methods recommended or to lose the trees. The people concerned must decide. 141—yv BIBLIOGRAPHY. CHESTER, F. D. Blight of Japanese chestnuts. 14th Ann. Rept., Del. Coll. Agr. Exp. Sta. for 1902, pp. 4445. 1903. GASKILL, A. The chestnut blight. 38d Ann. Rept., Forest Park Reservation Commission of New Jersey for 1907, pp. 4546. 1908. Hopson, E. R. Extent and importance of the chestnut bark disease. Cire. [unnumbered], Forest Service, U. S. Dept. Agr., Oct. 21, 1908. MERKEL, HERMANN W. A deadly fungus on the American chestnut. 10th Ann. Rept., N. Y. Zoological Society, pp. 96-103. 1906. METCALF, HAVEN. Diseases of ornamental trees. Yearbook, U. S. Dept. Agr., for 1907. Pages 489-490 contain an account of the chestnut bark disease. The immunity of the Japanese chestnut to the bark disease. Bur. Plant: Ind, U. S:Dept. Agr, bully a2ie pt 6. 1008: Morris, Ropert T. Chestnut timber going to waste. Conservation, vol. 15, no. 4, p. 226. 1909. MURRILL, WILLIAM A. A new chestnut disease. Torreya, vol. 6, no. 9, pp. 186-189. 1906. Further remarks on aserious chestnut disease. Jour. N. Y. Bot. Gard., vol. 7, no. 81, pp. 203-211. 1906. A serious chestnut disease. Jour. N. Y. Bot. Gard., vol. 7, no. 78, pp. 148-153. 1906. The chestnut canker. Torreya, vol. 8, no. 5, pp. 111-112. 1908. ——- Editorial paragraph in Mycologia, vol. 1, no. 1, p. 36. 1909. Spread of the chestnut disease. Jour. N. Y. Bot. Gard., vol. 9, no. 98, pp. 23-380. 1908. REHM, H. Ascomycetes exs. Fase. 39, No. 1710. Annales Mycologici, vol. 5, NO ode eee OL OO Ke STERLING, EH. A. Are we to lose our chestnut forests? Country Life in America, vol. 15, no. 1, pp. 44-45. 1908. 141—-v 54 INDEX. Page. Acids, organic, effects on nicotine’ content of tobacco...........------------- 11-13 Dn Mom Wels OMm sOrtns U1 Mieokine._.2-\.. 2-2... 2k. ee 9-11 amere orien oO: Granvilie tobacco wilt..........0....--.2...2.---.- 00-24. 18 Bacterium, Granville tobacco wilt, method of entrance..........-.-..------- 20-21 Bark disease, chestnut, present status, peper ..........-.....----------.---- 45-55 See Chestnut bark disease. an. 2 iomus-veive., and its history, paper. .....:.......-ss.-..-2-4..----- 25-32 UT DU RES SCC Aas se Nf a PS oe A 25-28 . es ll ae eS) Ae REN oe ge Ce oe eR 28-32 Deammumranny Of chestnut bark disease..© - .-.. 2. =~ sn. 2-60 seg ees eendet 5d Bort, KATHERINE STEPHENS, paper entitled ‘‘The Florida velvet bean and its eS Bee FOR I et 2 Ree ape oe neg ns en oe eee 25-32 Peerier Drond, 1) COM, Importance, papers... .. 4... 2... 82560 55-6-22-4-. 33-44 corn, development of present methods.-.-....-..--......---------- 34-36 penn were cnemee. Dihlioeranny..--. 222... - 222-25) A<2.-2 25520 o5e5t 55 Reap Arne Sy TOs so 8 Byes en sn ede sie ea SL 47-48 control by destruction of diseased trees. -..-.---.---- 50 inspection of nursery stock ......-.------ 49-50 treatment of diseased trees --------------- 50-52 NEEM ete oer Sek ye a ie Ses oes ues oe 45 Pepe Meret EAE 2 SS eo oa: 45-47 Mi ERODE ah roe ete oe ee oS ee Se 45-55 rericnoen OF spread, methods). 25 62s 222. 22222 49-52 Co.uins, Guy N., paper entitled ‘‘The importance of broad breeding in corn’. 33-44 J. FRANKLIN, and Metcatr, Haven, paper entitled ‘‘The present grams of tne chesimit bark disease’’.... 2... -. 2. 22 0et 5 a2 45-55 Corn, breeding, development of present methods ----..-------------+------- 34-36 Brean prcemine. 1Mipemiamce, Paver <2. 2 2 oe sn eee 33-44 continuous improvement through selection..-......------------------ 41-42 culsural fendencies toward imbreeding ...---...-.:--.-.+2.-5-+----.-- 37-40 Sg Oo 7: ene a a a 41 Damani OG MPI ot ne oo Soe oe ee tee ee eke oes the 36 Disease, arn, chestnul, present statis, paper... 222542252 -2.2+- 2-5-2. -- = 45-55 See Chestnut bark disease. pete es AOAC MuWUl, Pier 5 222 oo. Poo acl, alae s be awning eyo -'e 17-24 Fermentation of tobacco, effects on forms of nicotine......-.....-..-.--.---- 9-11 Pima weve, peamand tie history, paper o 220025. -2..225.26.. 24. 2-2-2. -- = 25-32 See Bean, Florida velvet. GARNER, WIGHTMAN WELLS, paper entitled ‘‘The relation of nicotine to the enn CAS ee ee eee ee le ol ce Late wd 5-16 Paap saiacro wilt paper sn oo2 Ys 2 et fas oe he oe oes 17-24 See Tobacco wilt, Granville. Puipotianes of broad breedine incom, paper..2-...22. +. -2 2 2 See ose 45-55 Nicotine content of tobacco, effects of organic acids......---- to wi ie Hh ee 11-13 relation to quality 222 2293325 S252 a ee 6-7 ‘ strene thy 2. Vou eee ee eee 6 Warlation see soe See ane ae ee ce a 5-6 fOTMS . 2.24. o- eo ee eee oS Se Pe ee eee ee 7-9 effects of fermentation and aging? =- 592 9225 22 a= 25 eee 9-11 relation to quality: of tobaccompapern= = asso -— ee oe ee 5-16 See also Tobacco. - Nursery stock, diseased, inspection for chestnut bark disease.....-.-.......- 49-50 Present status of the chestnut bark disease; paper. = so =. a= ns ee 45~55 Relation of nicotine to the quality of tobacco, papers. —-2-— 6. ae 5-16 Selection, corn, means of continuous amprovemenite sss. s.= eee eee 41-42 SmitH, Erwin F[RrInxK], paper entitled ‘‘The Granville tobacco wilt’’....._- 17-24 Smoke, tobacco, composition =. 22 = Bas ee ee 13-16 Tobacco, aging and fermentation, effects on forms of nicotine...--.........-- 9-11 nicotine content; etiects ol oreanie acids= 49-2 as ae ae ee 11-13 relation) to qualitive ssa" s=es2- so" RMN ces trys 6-7 “ssGrem ela? ee nthe Ae a Se ee 16 VaTIAblon. 5.1 ae Eee eo eee eee 5-6 effects of fermentation andlagin® 225) 2s =e ae ene 9-11 forms. -.2 ses. SoU ee ee 7-9 quality, -relation of nicotine, paper == sns- aes = oe a ee 5-16 total nicotine ‘comtente es). - = 6 oa eee 6-7 See also Nicotine. smoke, composition ..2 == 222 G2 222 a See os eis eee epee eg ee 13-16 “‘strength;”’ relation of micotime content: === sae. = eee 16 wilt; Granville, paper = 22. Use Noe ae Se ae 17-24 bacterial orig pms i ee ee 18 continued prevalence: = 22 Cas ae) eee 17-18 experiments: 922 a eee 19 germ involved estos eh ere eee oe en eee 20 history. 9. .ts4 --2----- eee 20-21 remedies‘and! palliatives, 65.2222 22245- 2 eee 21-24 Trees, diseased, destruction to control chestnut bark disease............-..-- 50 treatment to control chestnut bark disease.................- 50-52 Wnitormity im breeding) contusion resaraimg Lenn sa ee = eee ae 36-37 corn Not essentials 7-2 ee ee ee ed 36 Velvet bean, Florida,-and its history, papers. ee oe ee 25-32 See Bean, Florida velvet. bg Wilt, tobacco, Granville; paper: + 2+ seen ee ee eee ee ere ee ee 17-24 See Tobacco wilt, Granville. [Bull. 141] } ; ts Bees " [Continued Som page 2 ey eover.] i ticeovtae: the Quality of Wheat. 1905. Price, 10 cents. | 9. Variability of Wheat Varieties in Resistance to Toxic Salts. 1905. BY 80. Agricultural Explorations in Algeria. 1905. . Price, 10 cents. ee Ev lation of Cellular Structures. 1905. Price, 5 cents. 82.6 Lands of the South Alaska Coast. 1905. Price, 10 cents. eit -- 83. The Vitality of Buried Seeds. 1905. _ Price, 5 cents. aa; i ode ee 84. The Seeds of the Bluegrasses. 1905. Price, 5 cents. , =e - 86. Agriculture without Irrigation in the Sahara Desert. 1905. . Price, Scents. _ °. 87. Disease Resistance of Potatoes.1905. Price, 5 cents. is 88. Weevil-Resisting Adaptations of the Cotton Plant. 1906. Price, 10 cents. AP __ 89. Wild Medicinal Plants of the United States. 1906. Price, 5 cents. | 1 aia * 90. Miscellaneotis Papers. 1906. Price, 5 cents. CBs of. _ 91. Varieties of Tobacco Seed Distributed, etc. 1906. Price, 5 cents. ; 93. The Control of Apple Bitter-Rot. 1906. Price, 10 cents. 94. Farm Practice with Forage Crops in Western Oregon, etc. 1906. Price, 10 cents. 95. A New Type of Red Clover. 1906. Price, 10 cents. Sig) Sone one - 96. Tobacco Breeding. 1907. Price, 15 cents. “i . . aha 98. Soy Bean Varieties. 1907. Price, 15 cents. . ec - 99. Quick Method for Determination of Moisture in Grain. 1907. Price, 5 cents. ae te es _ 100. Miscellaneous Papers. 1907.. Price, 25 cents. hee eee OR ~ 401. Contents of and Index to Bulletins Nos. 1 to 100. 1907. Price, 15 cents. Be ee * 102. Miscellaneous Papers. 1907. Price, 15 cents. Ae bene: oO 103. Dry Farming in the Great Basin. 1907. Price, 10 cents. “si ) gee Shere 104. The Use of Feldspathie Rocks as Fertilizers. 1907. Price, 5 cents. Se 105. Relation of Composition of Leaf to Burning Qualities of Tobacco. 1907. Price, 10 cents. — Mert wy eA, 106. Seeds and Plants Imported. Inventory No. 12. 1907. Price, 15 cents. ‘ Be et Pe — 107.. American Root Drugs. 1907. Price, 15 cents. ogee uk ei ‘2 ~_ 108. The Cold Storage of Small Fruits. 1907. Price, 15 cents. : 4 TN PH oe ae pete j Price, 5 cents. - 109. American Varieties of Garden Beans. 1907. Price, 25 cents. ~ 110. Cranberry Diseases. 1907. Price, 20 cents. | = aE An “Miscellaneous Papers. 1907. Price, 15 cents. “e eh aa eee 112. Use of Suprarenal Glands in Physiological Testing of Drug Plants. 1907.. Price, 10 cents. - oe Se . _ - 113. Comparative Tolerance of Various Plants for Salts in Alkali Soils. 1907. Price, 5 cents. axe ae j _ ‘114, Sap-Rot and Other Diseases of the Red Gum. 1907. Price, 15 cents. paiea ak . 115. Disinfection of Sewage for Protection of Water Supplies. 1907. Price, 10 cents. ae 3 2 iets alee _.-:116. The Tuna as Food for Man. 1907. Price, 10 cents. cates =! a a __. 117: The Reseeding of Depleted Range and Native Pastures. .1907. Price, 10 cents. , CT ene 118. Peruvian Alfalfa. 19077 Price, 10 cents. ; Boo he 119. The Mulberry and Other Silkworm Food Plants. 1907. Price, 10 cents. es Sane 120. Production of Easter Lily Bulbs in the United States. 1908. Price, 10 cents. ; A dias _ 121. Miscellaneous Papers. 1908. Price, 15 cents. aoe es | ‘ ac,