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(^16) 288- 5989 -Fo« i ri ) if ii I- i -ill 3)!!: * » # •■ ^EP »r» '« • I DOMINION OF CANADA DEPARTMENT OF AGRICULTURE ENTOMOLOGICAL BRANCH C. GORDON HEWITT, DOMINION ENTOMOLOGIST THE PEAF THRIPS {Taeniothrips inconsequens Uzel) AND ITS CONTROL IN BRITISH COLUMBIA BY A. E. CAMERON, M.A., D.Sc. AND R. C. TREHERNE. B.S.A. Field. Officers BULLETIN No. IS Published by direction of Hon. T. A. CRERAR, Minister of Agri. re, Ottawa OTTAWA J. !>■ LABROQUERIE TACH£ PRINTER TO THE KING'S MOST EXCELLENT MAJESTY l»I8 Price b cenU. ISSUED MAY B. I91l> ijj; si 'i . • t . .t ii ;is .1' I'- ll' ill « M i i i««l I t. It >; t '.... ...!-■■■ i :•)■-"- _. ^ ■- . " .i", ^ t \ - ,# ■■^-'f. V t k- ir-.' : • > ■«.. /■■I "■> K-i ;-^i-:' ;'..■.-.?.■., • •<' ... DOMINION OF CANADA DEPARTMENT OF AGRICULTURE ENTOMOLOGICAL BRANCH C. GORDON HEWITT, DOMINION ENTOMOLOQI8T THE PEAR THRIPS (Taeniothrips inconsequens Uzel) AND ITS CONTROL IN BRITISH COLUMBIA BY A. E. CAMERON, M.A., D.Sc. AND R. C. TREHERNE, B.S.A. Field Officers BULLETIN No. 15 tr ttl I' \ Publiihed by direction of the Hon. T. A. CRERAR, Minister of Agriculture. Ottawa tl '4 x> OTTAWA J. Di LABRuQUERIE TACH£ PRINTER TO THE KINGS MOST EXCELLENT MAJESTY 1913 [ISSUED MAY 8. 19ll> 36197—1 If ii '■ i ■ ll m Ottawa, Jaiiuarj- 22, 1918. The Honourable The Minister of Agriculture, Ottawa. Sir,— I have the honour to submit hr- jiritb for your approval Entomological Bulletin No. 15, entitled " The Pear 1 ips (Taeniothrips incoruequeru Uiel) and its Control in British Columbia " uich has been written by t>. a. E. Cameron and Mr. R. C. Treheme, Field Officers. In many commercial and other orchards on Vancouver bhint. ' .e has been for a number of years a very serious reduction in the crops of apples, plums, prunes, and cht ries owing to a cause which could not be determined. In certain cases, well-cuUivited orchards were almost wholly unproductive. In 1915 the pear thrips was discovered in the region in question, and we soon determined that it was the factor responsible for the losses which the fruit growers were experiencing each year. This was the first anu only record of the occurrence of this insect in Canada. In view of the losses for which it had already been responsible in the infested region in British Columbia, the serious damage it was causing in the states of California and New York, and the importance of checking its spread in Canada, we immediately undertook an investigation. The life-history, habits, and control of the insect under British Columbia conditions were studied. After determining the most satisfactory spray and suitable methods of application, demonst'-ntion work in c mmercial orchards was carried on. The practical results of this i.. , Tstigation h been of signal and immediate benefit to the fruit growers in the infected ret ; in one of the orchards the crop was increased tenfold lait season bj the adoption of control measures. Notwithstanding' the occurrence o*' i his pest in the state of New York, it has not yet been found in nv aart of C. hnJa other than Vancouver island and the adjacent islands in Brit : Columbia. It is very important, however, that a very careful watch should be kept for its first appearance in any other of the orchard sections of British Columbia or in eastern Canada. I have the honour to be, sir, Your obedien^ servant, C. GORDON HEWITT, Dominion Entomologist, I: I't; ' « F l!-;-b 36197—2 hi'*'- b3 We shall be pleased to hear from any one concerning damage or trouble of any kin 1 due to insect pests. No postage is required on such letters of inquiry when addressed : — Dominion Entomologist, Department of Agriculture, Ottawa, Ont. Such inquiries should be accompanied in all cases where it is possible by speci- mens of the insects. The insects should be sent packed with their food plant in a strong wooden or tin box to prevent loss in transit. Packages up to 12 ounces in weight may be mailed free, and every package should bear or contain the sender's name and address, and be accompanied by a le' ter. tuble of inquiry f speci- )Iant in inces in lender's CONTENTS. PAOI Summary 7 Introduction 9 Historical — Known distribution 10 History of species in British f^olumbia H Distribution in British Columbia H Synonomy of the species and its systematic position The Order Thysanoptera 12 Common names .!..........!.... 12 Life-history — The Eir— DescriptioB 13 Period of em-laying 13 Duration ofen-staae 13 Emcapacity of adult Ij The l«rva--^«criptioB .......'. 17 First-state larva 17 Second-staae larva 17 Duration of larval stage Ig Number of moults 18 Depth of larvc in the ground 19 The prepupa— Description 20 Duration of prepupal stage 20 The pupa— Description 21 Duration of pupal stage 21 The Adult — Description 22 Duration of adult stage 23 Longevity of adults in captivity 23 Migration of adults from soil to tree 24 Determination of the date of adult emergence 25 Emergence ofadults in relation to temperafire 29 Habits- Food plants— Native and cultivated 31 Susceptibility of fruit trees to attack 33 Damage to pears 33 Damage to apples 35 Damage to prunes 37 Damage to cherries 37 Reproduction — Ovipositioa 3g Parthenogenesis 41 Control of the pear thrips— Spray mixtures 42 Hiscible oil No. 2 42 Whale-oil soap 43 Nicotine sulphate 44 Lime sulphur 44 Arsenate of lead 44 Results of spraying 45 Method of recording results 45 Value of two and four sprayings 45 Value of early and late sprayings 4S Budding chuactertiaics of trees 47 When and how to apply the sprays 48 Climatic factors 48 Cultivation 48 Schedule of applications 48 Preparation of spraying mixtures 48 Types of machines and noiiles tO Acknowledgments SO References 80 jl 'i ml'} Ft' ,^ I: Mil H 36197—21 ILLUSTRATIONS. Fio. 1.- 2.- 9.-' 10.- n.- 12.- 13.- 14- 15.- 16.- 17.- 18.- 19.- 20.- 21.- 22.- •The pear thrips, Ttteniolkripa incoiuequens; eggs. i93 13 Mica-chimney cage in position on a pear twig as used in oviposition experiments with pear thripa. 15 ■The pear thrips, Taeniotkripi inconaequeiu; larva recently emerged from the egg, ventral aspect. X 200 17 The pear thrips, Taeniothript ineoiuequem; full-grown larva, dorsal aspect, x 90 18 ■The pear thrips, Taeniolhript inconsequem; pupa, first stage, dorsal aspect, x 100 20 The pear thrips, Taeniotkripi inconse^uem; pupa, second stage, dorsal aspect, x 100 21 The pear thrips, Taemolhript inconaequeiu; adult, wings outspread, x 95 22 Duchess apple buds. May 3, 1917. Adult pear thript may be seen on the bud on the right- hand side 25 Trap emergence-box used in the orchard at Royal Oak, Vancouver island, 1917, for deter- mining the first appearance of thrips in the spring and their numbers in the soil. 26 -Combined trap-cone and cylinder of tin used for holding the glass vials, and fitted into the holes of the soil emergence-boxes, in the orchard at Royal Oak, Vancouver island, x 2 27 -Inverted, muslin, bag-net trap in position; a convenient method of deteimining the dates of emergence of adult thrips from the soil in the spring 28 -Straight-line curve showing emergence of adult pear thrips in trap cages under trees in orchard, Royal Oak, Vancouver island, March 28-April 25. Dotted curve is a graphical representation of average daily mean soil temperature during the same period 29 -Showing a destroyed blossom-bud and an injured blossom-cluster of the broad-leaved maple, Acer macropkpUum, May 8, 1917. Injury caused by the feeding activities of the adult pear thnps 31 -Egg-scars on the leaf-petioles of the broad-leaved maple, Acer macropkyllum, sifter eggs of pear thrips have hatched. May 31, 1917 32 ■A, Blossom buds of Bartlett pear; B, Olivet cherry, showing destruction by the feeding activities of adult thrips in early spring 34 -Egg scars on young develoning apple-stems. May 20, 1917. Larva) of pear thrips have emerged, rupturing the tissue and thus accentuating the scars. The pubescence of the stems has been partially removed to show the scars more clearly enlarged. 36 ■Olivet cherry infested by larva of pear thrips, May 31, 1917 37 Immature Olivet cherries showing chaiscteristio " russetting " caused by the feeding activities of the larve of pear thrips. May 31, 1917 38 ■The pear thrips, Taeniotkripe iseoiueQiMiM,- terminal abdominal segments of adult, to show the ovipositor, x ISO 39 ■Transverse section in outline of fruit-stem of Italian prune, to showetgf«hambers («.c.)in the outer layer of cells (cortex) . Drawn from actual specimen, e, epiderm ; e. cortex ; ee, chlorophyll layer of cortex; e.k., hair; e.c, egg-chambers; f.v.b., fibro-vascular bundles; m., pith, x 115 39 Transverse section of cherry stem to show the egg-chambers (ex.) in the outer layer of cells (cortex), e. Head of larva (I) recently emerged in egg-chamber also shown. Drawn from actual specimen. x6S 40 ■The pear thrips, Tamiotkripe incontequens. Adult in the act of ovipositing in fruit-stem of apple; ovipositor extended and represented asembedded i- theplant tissue, x 126. 40 THE PEAR THRIPS {Taeniothrips incomequens, Uzel) AND ITS CONTROL IN BRITISH COLUMBIA. By a. E. Cameron, M.A., D.Sc. AND R. C. Treherne, B.S.A. Field Officers. SUMMARY. For many years orchardists of Vancouver island have annually experienced a decided reduction in their crops, owing to a " blighting " of the Sm budV fTi ?oX .T^^t •"/'^t.'S'^!; -^^ *^^* ^^^ '°«« ^^ attributedTo spring iLkL' Tvr * iwif ^^.^'^''^•^ certain orchard sections appear to be peculiarly mi-* ^°* ^^" ^^^ A&mf,fi,e, however, could be ascribed to this c^se. In T^t-tt^^ discovered that severa orchards were overrun by the pearthrips, Taenwthnpa incomequens, and to this insect alone the greater propor^on of the damage is now known to be due. The minute, glossy-brown insect meMure^ PnH"of°M*T*''!,\^^ ''I •'?''^™ ^"«th, and is^sullly fim observedTth^ end of March and the beginning of April actively moving around in large fiHlv nr«*',^l P ""P?"'"** ^^^^' ^?"^*th the enveloping scales of which thfy iSe^^c^ltse^rrmlSh^s'^^ ""'^"*"" ^" '""^ '''''' *^^^ ^^ ^een dormant Life-history. The emergence from the soil continues up to the middle of April, the maxi- mum number appearing from April 1 to 14. This practically coincides ^th the time of the bursting of the buds of the various fruit tree^s on vSo^er ™l\iT * /•' ^''''% ^?^^'/ °'?^°?'* '^^^'^ ^^^ ad»'t« enter and feed on the young delicate tissue of the developing parts within. Almost as soon as the leaves and blossom pedicels appear, the adults begin to lay their eggs. The SHff*^f tJ^ generally laid about the middle of April, and the last Kbout the middle of May. The period of maximum oviposition usually extends from April fL? ^^ *u ^^^^ f""" '^'? '" '^«,^'* numbers on the petioles and midribs of Sf lt^r'V°" the outer surface of the calyces of the young fruit, as well as on nrnhlK! ikT^K ^^^V^'i'}'^^ about fivc to Seventeen days to hatch, and it is probable that the great majority hatch in about fourteen days under the con- ditions prevailing on Vancouver island. „«„if™°j*' P'""u *°^ cherries, which are more tardy in their development thi.n apples and pears by almost a week are attacked later by migrating individual:'. Sn T^'^^r'?"^ •' ^^^^^^'^ °y ^^^ ^""^^ °^ t^'esc fi'^t i« proportionally greate^ than what obtains on apples and pears. It is well to bear in mind that the most before^Somln ^^^^ '^ associated with the buds just after bursting and K„ t ^^A '^'^f "J*"*^ *''*'.'■. ''"* appearance at the beginning of May, and are to TnlS "♦K °" J*"' ^'^^' ';"*u" *Jl^ "'^'^'c of June. In great abundance they occur inside the calyx-cup of the blossoms, lacerating its tender tissue and feeding on the nectar. They are also to be found on the back of the leaves, shaded from the sun, busily sucking the leaf-juices. When at rest, they are generally to be found ranged along each side of the midrib and chief veins. When the larva .■»J": m ': i II J'! 8 attack the young fruit in numbers, they cause a " russetting " of the skin which is known as " thrips scab." They appear in maximum numbers from May 20 to June 5. The individuals remain on the trees for about three weeks before they are fully fed. When mature, the larvte fall to the ground which they enter by any con- venient crevice or crack. They may penetrate quite deeply, depending on the character of the soil. In the clayey soils of the Saanich peninsula no larva was found below a depth of 15 inches. The greatest numbers occur nearer the surface, at about 6 to 10 inches. Very few are found to occur in the surface mulch of cultivated orchards. In uncultivated orchards, quite a number of larvae penetrate no more deeply than the stratum of interlacing grass- and weed- roots. They remain in the soil for three to four months before transforming to prepupae in their tiny earthen cells. The prepupal condition lasts for only one week to ten days at the end of September and the beginning of October. The prepupae tran-form to true pupae, the last of which are found in November. The great majority of the pupae remain as such for six weeks to two months. During November the pupae become adults, and in this condition they remain in the soil for about five months. At the end of March and the beginning of April of the following year, they omerge from their winter quarters and make their way to the trees. There is but one brood of the species each year. Remedial Measures. As a result of a thorough study of the various remedial measures for the pear thrips undertaken diu-ing the springs of 1916 and 1917, it may be confidently stated that this insect can be readily controlled. Spraying offers the only satisfactory means of combating its ravages, and the energies of the orchardists must be concentrated to cope with the adults and larvae on the trees in the spring. It is primarily essential that the orchardist should learn (1) to recognize the thrips, (2) to watch very carefully for its first appearance on the buds. By following this advice the first step in control will have been accom- plished. It has been conclusively shown that spraying against the adult thrips is more important than against the larvae. Hence, if circumstances demand the application of only two sprays, it is better that they both be applied before blossom- ing rather than one spray before and the other after. Three sprayings may be arranged for in instances of severe infestation, in which case two applications arc made before blossoming and one after. In the case o." h moderate degree of infestation, two applications of spray are alone necessary. Both of these should l>e made at a time when the thrips are observed to be " running " on the outside of the buds. Usually the first application is made on a bright warm day in spring after the buds have just begun to burst. The second may be made in the week preceding the period of maximum bloom. The third spray is directed against the larvae in the calyx-cups and on the leaves just after the fall of the petals. It has been demonstrated that for the first application the best results attend the use of miscible oil No. 2 in combination with nicotine sulphate. Whale-oil soap, also combined with nicotine sulphate, is the most suitable and economical for the second antl third sprays. Lime-sulphur has been shown to possess very poor penetrative and spreading qualities, hence its potency as a controlling agent for thrips is merely confined to those insects with which it comes into direct contact. Therefore it should only 'le used to replace the second and third api)lications of whale-oil soap in cases of light infestation and wherc^ it has been found necessary to undertake control measures for " scab." On no account must it be inferred that the first application of miscible oil can bi dispensed with. Miscible oil, by rem'on of its greater powers of penetratinu the young buds, has been found to be the best remedial ajp^ent in the first spraying. The use of whale-oil soap at this time, whilst often satisfactory, is less effectivi than the oil. 9 INTRODUCTION. The pear thrips, Taeniothripa inconse^juens Uzel, w-iS discovered on Van- couver island for the first time in the spring of 1915 in an orchard at Royal Oak, four niilM norta of Victoria. Previous to this, the insect had not been observed m British Columbia. It is probable, however, that it ht^ been present in the province for at least ten years, if not more. In the opinion of orominent orchard- ists, the characteristic injury r-aused by the pear thiips to the buds of the various deciduous fruit trees, has existed more or less in their orchards during that period; but the damage was not associated wi''i the presence of this apparently insignificant, but very important, pest until 191.5. The fact that, in the absenc of treatment, the average annual loss due to the thrips in the infested areas of California, is computed at over $2,000 000' —a figure which would naturally increase with time— has been more than sufficient incentive to an early combating of its activities in the province of British Columbia. Three separate r 'd badly infested districts were selected in order to prosecute investigations, all situated on the Saanith peninsula of Vancouver island. At I * o^' '" addition to the general or ird spraying, a small section containing ^jout 200 trees was set apart for the p pose of experiment and demonstration. Here, too, a laboratory was established by the Entomological Branch of the Dominion Department of Agriculture, to facilitate the undertaking of an extensive and intensive study of the life-historv and habits oi the pear thrips. At the two remaining centres, Keating and Gordon Head, a campaign of experi- mental spraying was undertaken as at Royal Oak with a view to discovering the most sat'sfactory and economical means of controlling the pest under local conditions. It is not possible to give figures with any degree of accuracy illustrating the loss ol cro) that occurred annually on Vancouver island. It can be quite confidently - .ted, however, that in the last seven vears the prune and pear crops have been a negligible quantity in certain sections. The trees have produced a wealth of blossom and the prospects appeared bright for an excellent return of fruit, which did not, however, materialize. In some cases the fruit buds were destroyed no completely that the blossom never appeared. The same symptoms were apparent in the case of cherries. Only. a.s they are more productive than prunes, generally quite a large percentage of the blossoms set fruit. lu pears, some varieties appeared to be more susceptible than o.ier;,<\nd the difference of altitude seemed to be directly associated in some casco with lesser or greater infestation u.' an individual tree. Generally speaking, it was founa at Royal Oak, at lep.st, that the pear trees situated on low-lying ground sufferen more than those on higher positions. Apples aa a whole are more robist in their growth than the other trees just mentioned, and although the infestation on some varieties, notably King and Baldwin, is mo»t severe, they do not apnear to suffer to the same extent a^ the other deciduous trees. Not only does the tb.ips levy a heavy toll on the fruit crop oach by damage to the fruit buds, but the atroi>hy of these buds, as well as the .iage buds, caused by the indiscriminate feeding of the insect and its larvse, tends to check the natural development of tl'c tree. As a consequence, where the control of the pest is neglected, there is a progressive diminution in the vields from year to year. The purpose of this bulletin is to call attention to the damage caused by this pest in the orchards of Vancouver island, and to the danger of introducing It into those of the mainland of western and eastern Canada, as well as to record the results of experimental spraying in its control. At the same time, new facts concerning the life-history and biology of the species under the conditions prevailing in Vancouver island are set forth. ' JJ 1-V 10 HISTORICAL. Known Distribution. Since the d'scovery and description of the pear thrips in Cnlifomia la 1904 by Miss S. M. Daniel,* the presence of fit species iu other •'art* .,{ the American continent has been demonstrated. It was not uatil the year 1911 that Parrott' f u « ^^ thrips (Taeniothrips pyri) in New York state, in pear orchards of the Hudson valley around Germantown extending from Stuyvesant in the north to Tivoli in the south. It wps also recorded by him from apple buds at Geneva, N.Y. According to Foster and Jones,' the pear thrips was forwarded to them in May, 1912, by Quamtance of vhe United S*,ates Bureau of Entomology The specimens were taken in six different orchards at northeast Philadelphia, in tht state of Pennsylvania. In the year 1914, Scott* recorded the pear thrips from a small KieflFer pear orchard near Baltimore, Md. The insect was also taken on some neighbouring peach and apple trees, though not seriously damaging them. In Europe, CoUinge collected seve'.l specimens from plum blossoms at Evesham in Worcestershire, England, which Bagnall' identified as EiUhripa (JaentMirtps) pyri Dan. Theobald* of the South Eastern Agricultural College, Wye, Kent, England, pays particular attention to the sne-ies in his Report on Economic Zoology, for 1910. Williams' records the occurrence of the species under the name Physothripspyri'D&mel, from Histon near Cambridge, England, in 1911 and 1913, and also believes that larvae sent from Cirencester belong to the same species. This author says there can be no doubt but that the thrips has been present in England for many years, and must occur in many localities. Mokrzecki' in his report of 1912, published in 1913, refers to the discovery of the pear thrips on apple and pear trees in the Crimea in March, 1912. With the exception of these records from the south of England by Bagnall and Williams, and from the Crimea by Mokrzecki, Taeniothrips inconsequena had not, up to the time of its discovery in British Columbia in 1915, been found to occur outside the United States. It is very probable that it will yet be recorded from other districts on the American continent, for it seems hardly credible that this insect only exists in localities so widely separated as California and British Columbia on the one side, and New York, Pennsylvania, and Maryland on the other. It is feasible to suppose that this markedly discontinuous distribution can be best explained by the supposition that the insect has been imported from one continent to another and fro^i one state or province to another on nursery stock. It canno' be argued that the insect is indigenous to British Columbia, notwith- standing its discovery on native trees, because it has not so far become established on the mainland. In the districts already named, certain favourable conditions, climatic or otherwise, have caused its rapid multiplication to such an extent that It has overflowed from its cultivated food-plants to native trees where it has assumed, in some cases, an undeniable economic significance. Especially i? this true in regard to maples. -By reason of the fact that on this continent the insect was first found in California and on pear trees, it is often popularlv designated the " California pear thrips.*' Under date of June 6, 1916, a letter was received from Mr. C. B. Williams. in which he states that the pear thrips must in future be known as Taeniothrips mconsequens Uzel, as it happens to be identical with an old-known European species. In a paper* dealing with British Thysanoptera he suggests the probabI< introduction of the species into the United States of America from Europe in the larval stage among the soil adhering to the roots of fruit trees. 11 HisTORT Of Species In British Columbia. D r- ^u "^^u" °^ ^^^^' * prominent orchardist, Mr. T. A. Brydon of Royal Oak, B.C., had been engaged in spraying his apple and pear trees with lime-sulphur .s^olution in order to combat " scab ", Venturia pomi Wint, and Venturia pyrina .\derh. His attention was attracted to the scorched appearance of the buds on several trees, and concluding that the injury was the result of the treatment, he at once ceased operations. Later, he observed that both sprayed and unsprayed trees had a similar damaged appearance which seemed to dispel all doubts that the hme-sulphur had eau.sed the blighting of tho buds. A com- munication seeking advice on the subject was straightway sent by the orchardist to Mr. R. M. WiT!slovv, Provincial Horticulturist, who with his a-ss-istant, Mr W H Robertson, diseovered specimens of thrips in th.- Brydon orchard. Simultaneously,' Mr. h. W. White, Field Inspector, acting und«>r the insv ructions of the late Mr. Ihomas t-unningham, Provincial Inspector of Fruit Pests, also visited this orchard and found the thrips. Specimens were submitted by Mr. White to .Mr. R. C. Treherne who tentativdy identified them as pear thrips, Taeniothrips l>yn Dan. This identification was later corroborated by Mr. S. W. Foster of California and Mr. J. Douglas Hood of the United States National Museum, \v ashmgton. Immediately on receipt of this information, the serious nature of the situa- tion wa-s reahzea. M the suggestion of Mr. Winslow who proved him If very energetic in facing the problem, a series of Farmers' Institute meetings was held in the Saanich peninsula of Vancouver island. Thorough examination of several orchards was made, and in ever case the presence of the pear thrips was de. . nstrated. Growers were quickly notified of the importance of the pest, and ai'yised to busy themselve? in preparing for a campaign of attack during the sprmg of 1916. Only one treatment for the larval thrips was made during the season of 1915, and thJg was achieved at Mr. Brj'don's orchard. In the spring of 1916, another serif of Farmers' Institu' ■ meetings was held, and plans ivere fully discussed preparatory to adopting measures for mitigating the injury likely to occur in the following season. Distribution In British Columbia. Our investigations have shown that the distribution of the insect is more extensive than was at first supposed. It has practicallv become established all over X'ancouver island and the adjacent islands of the Gulf of Georgia, wherever there lire orchards or maple trees. All the orchards of the Saanich peninsula are more or less infested, and reports of its presence on Gahriola island have been verified. Here, too, the maples bordering the shores of the island, showed a great deal of damage when examined on April 27, 1917. The blossoms had been practically killed, and the petioles of the blossoms (fig. 14) were badly scarred by reason of the oviposition of the adults. L^ier in the season these trees developed a very poor foliage. Even the shade n.aple-trees in the city of Victoria itself have not escaped, and the few fruit tref s which almost every householder possesses are suffering from thrips attack. In a thorough search of the district extending from Victoria in the south to .^anaimo in the north, our efforts were reivarded by the discovery of the insec* practically everywhere, there being a particulailj heavy infestation in some o:chards in the vicinity of Duncan. It would appear that the species has not so far become established on the tnainla of British Columbia. A large number of the orchards in the Fraser valley trom Agassiz to New Westminster, including those of Hatzic and Mission, were carefully examined in 1916 and again in 1917, and although an unidentified species of Frankliniella was encountered, not a single specimen of the pear thrips was found. Similarly, a close watch for its occurrence in the orchards of the Okanagan has so far proveil negative. 36197—3 \ ill 1 ih i u a P ft 12 When one realizes the comparatively narrow waters which separate Van- couver «land from the mainlan.l. and the frequent intercours^ that occ5« between the two places, it seems difficult to 8up,i,se that the speci^couW n^ be earned to the mamland orchards from the islalTt with nurssry^sS The"2 wlf^h f^f h'*'''"'^' "P^^ l^'' orchardists of the mainland to m^ntain a carS watch for the species and to report its presence wherever it is found. SYNONYMY OF THE SPECIES AND ITS SYSTEMATIC POSITION. Most authors who have dealt with the species have referred it to the eenus th^^T f"*^'""'^"!'""'.^'^'^- H^*^''" •^°*«^«^ «ta*e« that according to the laws of nomenclature this name must be replaced because it was first use to designate a sub-genus substituting the term TAnp,, itself SemDloved Ih^^a^fh"' ''^^rr ^'""^ ^U^^^- '^*>« ^"t*>°'-' therefore, decid^^t^Te bgate the pear thrips to the genus Taeniothrips of Amvot and Serville whilst he i^nJr^"^?//^ "^""T^'^^l '^l'^ previously assi^ed to A'u'a™' among the K^f. H ^r'^^^K*"""' f*^*'''*"^. Odontothrips, and Frankliliela IniS^ he partly adopted the method of Karny." Williams' already quoted, originally placed the species in the grnus Phyaothrips, but this name has now been discarded. ^ THE OrDF.R ThYSANOPTERA. To, Z^"^ /?''*''''■ ,'^^'^u"K'.'P**''""i^ mewhat broader anteriorly than po terioriy. It U whiti.h toIouHm with a very delicate chorion and no evident micmovl.. HnHn. inV,.»...i„- .i.„ ™ ."_""■ .\?i2"n®?J Period of egg-laying.~Aduh>i wen- first ohserveil to be engaRetl in ovipositinR about April 18 and contniued to lay their eggs up to about Mav 10, after which date no female wan seen to ovipost. Xeverthelefss, many stragglers and late individuals must continue to do so for several days later, which explains in part the presence of newly-emerged larva? towards the end of Mav. The period of maximum oviposition extends from April 24 to May 7, during which time the scars caused by the ovipositor on the petioles of ffuil and leaves, and on the midribs and veins of the latter become very apparent. Towards the end of the egg-laying season the under surface of the sepals, especially of apples, receive a goodly quota of eggs. Isolated cases of oviposition on the young fruit anil pistiLs were ob.served, more particularly on cherries and prunes, bat it is im- probable that the resulting damage, if any, seriouslv affects the crop yield. Jig. 1.— The pear thripti, Taeniollirips ineomfquenii; oH?». X 93. (Original). Duration of egg-stagt .—To determine the duration of the egg-stage a scries of efore the adults had emerged from the soil, thus en&urmg that no eggs could be laid by individuals other than those introKT o( Eipprimeat. I 2 3 4 5. a. 7.. 8.. 9.. 10.. P . 12. 13.. 14.. IS.. 16.. 17.. 18. 19.. Variety of Tiw. Numlicr of I-«Rs. DurhrM apple Gravriutpiu ' Red Cheek ' Bartlett pear.. Bosc Olivet cheiT>-. as 118 109 42 127 98 91 113 112 liO 4 153 128 113 112 63 49 49 120 Ntt '< .r of E«pi' iieni. 20 21. 22. 23. 24 25. 26 27. 28. 29 30. 31. 32 .^•^. 34 M 38. 37.. 38.. Variety of Tree. Numlier of Erich. Olivet ehcrry. Italian prune. Columbia plum. Bartlett p<«r.. 37 7 108 M 42 18 120 12S 37 4« 90 27 28 93 78 9 4 27 32 .In,, r* ^ ?K ^l"y fu^ "^t^""^ ^^"^ b"^ was a blo8sora-bud, more eKiw were deposited than where the enclosed bud was a leaf one. The pear thrips^ows a decKled predilection for the blossom pedicels as receptacles fo^r Hs egX ♦ h« J„if T "u °^®?f^ '*"* ^5' ^ ^'"K^« individual varies. In the experiment the highest number laid by any one was 153 eggs, and the lowest w J4 Und.T Z7m\riTlT^N'- P-^,t that t^ pear thripsTscaSe of laving manv is fhU Th!*' ^ "* '* " "'^t ''^''•y that every individual actually lav.s so manj as this The average, as calculated from the above table, is 73 but this may be considered lower than normal ' 8ake^oTlmniri!nn°"Tl*^^ °^"*^' ""^ ^5 mature specimens was made for the t^be. fivp nn 1T"m^^ -^T^ '" *. P^'^*^ "'K'^n consisting of ten ovarian tubes, five on each side, united posterioriy to form the oviduct. The oviducts of each side again unite to form the common oviduct opening to the ex orior S-cXanteSv"wh""' about twenty eggs besides^umVous immlure ?a™v bv d^tluX) 7 1 *^^ *" •'^•'' ^'-^ ''"ach-d to the walls of the bodv cavit> t)> delicate fibres of connective tissue. Normally, theref-.re the fullv deve'fpS.''""'^ ""'' "'*'•" ''' '"'^- '^'•°"* 200 egg^ 'at variou^' lil^lfsf tl.P Sk^ **''' ^^'"^ "^ oviposition and, indeed, throughout the whole snrimr rimX I °"< ^»"/'«".v«'J island i« frequently verv uncertain. Temperatures Srd XZJV A,..^?""'h'' 1 '^' P-vailink, cold, southS wlX hr^llitnt c. K- °t April and early m May matters improve considerablv bnlhant sunshme prev.^iling during the day, and the teni,>erature ascending to It will l)e readily seen on consulting table I on page 14 that no strict corre heTgrtThatcl'VoSr the air-temperatures''a'nd the timeTrec'utdTor Hz t* : . "o"Knly speaking, the period of incubation varies as tho rise of temperature but by no means proportionallv. It may be t»,at embedded fnfl!^^ Tk'^^T^^^^ the epidermis in the plant tissue, the eggs are not readd influenced by changes of atmospheric temperature ' 17 The Larva (tigH. 3 and 4). De»eription.—TMter ant" Jonm' have given a complete deMcription of the ZU^t. 7 II i'*,*"'"''^**' 1"«t«*- T*"' *l*^'-"Pt'«n of the pupa and the adult, which follow later, are also borrowetl from the same source. " Fiaar 8taoi (Labva 1 dat old).— Lenath 0't46 mm- width nf h«ul n im ...«. —lAti. i I ^1 ".ij' Jl^i 'lill* "• '^' '?" "• 'i™'-™' «>'»uf . «nin«lur,-nt white; wnoraUhmpe. (uiiforai Tfl(*M» hc«.l. and leg! I«ne in proportion to the rMit of the hody. ami unwie dy AntonMdi.ti.Mlv ^ ...ented, fi"t ««n,«t .Lrt. cylimirical ««,Bd «,m™, about ?w*;r..*i„„i"^fiSt o^S ij,^„^ third ■c«ment»TMchtly lon«er than wond. unmhaped; fourth alwut a. lon« " w«t o?iSiu t^SSJI' iiTBtely conical A few very fine coni.piru^»^. l\^^ x^^lZJ^'^L .ibniptly taperuw. with a frinne of lo-g. white. n.Mirly incoS.picuou.hairiL.-m ««it fe^ !Sd tTS newly equal >» lenirth; tarn oac ointed. ending in % .in«lc Clack claw." In SdhSn U T^t?.^ VhS a nn« of .mall denticle, i. provided on the pcMterio ma^n of the ninth «-i,n?nt of the aW^Tmr^ k Ml' ; ). ' I V. ' I Flo. 3.— The pear thrii- . Tirniiilkriit.^ iHcoHseqwriK: lar\-a recently emenciMl from theeKK, ventral aspect, x 200. (Orifdnnl). 0 l08-t*'mm''?e^*h'''f*"'':t''''""n'-.oV;''^'*'~T"''»' '<■'"«*' ' »«3 mm; Icnifth ..f head 01.5 mm: width 1083 mm, length of prothorax OVm mm, width 0-2186 mm; lenRth of mesothorai 0-18.^1 mm width J^nKth of antenna; 0 2833 mm: seament I, 26 u. II, .W u. Ill, 76 u; IV. 66 «.- V. 14 u; VI, II 466 nun. 10 J,- VII, 33 u. aliout narrow cylindrical M lnn„«« I =»^ t''^; »KI"'^nt.i; short, cylindrical: II, obtuse, spindle-shaped: III. spindle-shaped, , „!!J??it^ ^ .""V-T *?»'*'"''•: iV , nearly as Ions a-i HI, broader than the rest, subcortical : V, short, cvlinHrie?! AM- •'..'• °''*'"''-^'^"V''';''°'' ^"'^" *•>■"- '''• VII, twice ,» l,.ng as VI. narrower and V,. InwiLh =,Ki. ' ul *"">«Vf rsely striated and with a few inconspicuous wiiite hairs. General colour faintly i, .-ulm?-?.!^]?!. ' °''*M«'Iy fusiform m shape. B,Hly lonRitudimilly and luterally f.untly striated. Head 1 rna-nlr;.! -^ Jif" *• ^f'^ reddish brown, situated a little in ailvancc of th< middle; mouth cone '■™„?!;^.k'^'. ,"•*'■'/ as, long as the head, extcnilinn to the middle of the prostemum. Prothorax » '^ j'Ji"'"""^*' '^^^ reddish brown, situated a little in ailvancc of tht middle; mouth cone '-inrn tH^.K '-." 1?' as long as the head, extcniling to the middle of the prostemum. Prothorax •w^e J^H» "'i ^"u" '"»*<.. <^'/trt!"i!< P<«teriorly. Mesothorax anil mctathorai short and broad, 10.«.om»I?.i ?? y' "'•>«'l"al. "> 'enirth about as long as prothorax. Abdomen broad, gently rounded. I,m!^r ITiJ^i: "P^™* at segments V ar.rl VI; first eight segments subequal; segment IX distinctly «DiS™' *hr.!S* J?^' , posterior edge armed with a circle of strong, short, thick. wedRe-shaped not n,,;t» .. I ""'"'W'o"*' and me.e?t IX. Lateral edges of abdomen finely serrated, also with a few long, incon- emml- t.~i "»'?•«;'>"'•> are more prominent on segment X. Legs strong; femora and tibiiB about iquai, tarsi, one .jointed, ending in a single black claw." i: •r Id ^i 18 haf.i!^'"^"'" "( '«."'«' «(«l/«—App<'aring first about May 1, when the newl^ S? f'^'r ^^"^ ^^J activities, larvjB remain on the tr^8 until about tj middle of June. Immediately on emerging from the egg the larva Ss move slowly around as ,f taking stock of its surroundings. Aftir a Xrt btSv uIZ'^ the vegetable tissue with its mouth stylets and begins to suck up t liberated plant juices. Consequently, by reason of the compafative transpar^enc of the small individual one can observe t^,, alimentary canSl ijaduallv Zum^n ?e5«1?*'°* '*"'•**' ^^' imbibition of the green chloroplLtT As thrS feeds It increases m size; the original cuticle proves too small and is shed hirth r* "^ "l^^^ifi^^^ ?'«* "°"'* «<'<'»'^' in ««nie cases, two days' afte Xt Th*p° W l*^^ T* ," '"^l" *? "•«*»» ^l^y" «'d before this moult tak fn„nfi.„7 ^ '••"" l&^ along the dorsal median line, the larva reniainin inactive for some time before this happens. The legs and antennte are «^l^^mn withdrawn, and finally the body is extracted from^the old sheath. During th Via. 4— Thp pear thrips, Tofnialhript tncoiuequena: rull-Kn>wn larva, doraul aspect. I 90. (Original). process the original tarsal claws servo as organs of fixation ombeddpH in H,. i^,i , • 1 1 "^® . *"*^ second stadium are robust and verv active How, A «»,; A- ^'u'' ':'^"i'"Pfi for the development of the larva varies Normallv t lo dur^^lth ^^"-^ *\Tnr*''"'^ ^'"t '«^ temperatures such as were exSi. I during the spring of 1916, and especially from May 6 to May 12, when the m fh^tSKSr^/Xtrv^'.*-'' ^" -'-' «--^ b/exertingV5h5 .i.' xs 19 When mature, the larvae, now as large and sometimes larger than the adults, cease to feed and abandon the foliage for the soil, which they enter by any convenient crack or small aperture. The method of transit from tree ground IS rarely, if at all, voluntary. Instead of crawling down the branches and trunk, the larvae merely fall down. Strong winds and dashing rains remove a goodly number, and many, again, are carried within the old, falling calyces. It is stated, by one authority at least', that those individuals which fall off the trees when they have only partially developed, mostly perish, unless they can attain to full growth by feedmg on weeds or grasses lieneath the trees. Necessarily such immature larvae would succumb in cultivated orchards. This appears to corroborate a similar statement made by Moulton." In an examination of a .small neglected orchard at Royal Oak, overrun by weeds and grasses, on June 2 several larvae were found feeding on gra.s8?s. They had dropped from the overhanging leaves of cherry and apple trees. This would seem to discredit the idea entertained by some orchardists that it is advantageous to leave orchards m sod because of the difficulty which the larval thrips experience in working their way into grass-covered soil This view is evidentiv more imaginary than real, if one will only stop to consider the small size of these insects and the facility with which they can avail themselves of the most minute opening. When, added to this fact, one realizes that weeds and grasses offer sufficient nutriment f(ir undeveloped larvae to become fully fed, the argument for cultivated orchards seems to be strengthened beyond measure. Further, a series of experiments conducted by Moulton, has demonstrated the value of ploughing and cultivating as partial remedial measures in ridding the top layers of soil of the pupa. The protecting earthen cells are destroyed, and the contained pupa are either injured or killed. Since, however, many larva; penetrate beyonvl the depth to which deep ploughing can be practically carried out, this means of controlling thrips in orchards is not by any nieuus infallible or absolute. It has been observed, at Royal Oak, that .some larva" will, indeed, penetrate to a depth of lo to 16 inches. Further, it has been shown that with the chuss of soil with which we have had to deal, the loose mulch of four or five inches generallv contains comparatively few larvae. Larva>, after leaving the trees about the middle of June, remain dormant in the soil until September or ()ctoi)er, a period of from three to four months. Th«^ I)repupal condition is then assumed. In California, the average time of mh-% terranean larval existence is .stated by Foster and Jones' to be from five to six months, with a minimum of two and a maximum of eight months. Neither of these extremes was experienced on Vancouver island, where no larvie were found after October 3. li^' I . If DEPTH OF LAKV.E IN THE (JHOIND. After the larva; have penetrated the soil and found a suitable place in which to rest, they make for themselves a small oval cell, the inner walls of which are smooth and compacted. Doubtless the cell is fashioned by the active, rotatory movement of the abdomen in a manner characteristic of the pupae of many ( oleoptera and Lepidoptera. The length of the interior is approximatelv 2 mm., and the breadth about 1-5 mm. Here the transformations from larva to pupa and pupa to adult occur. The adults continue to occupy their cells in safety until the warmth of spring stirs them into activity. The distance to which the larvte descend in the .soil depends on the structure and texture of the latter. It is to be expected that in an open, porous soil characterized by thorough breathing, the larv* will penetrate deeply, whereas in a clayey, compacted soil, the mechanical difficulties to be encountered as well as a diminished circulation of atmospheric oxygen, will tend to confine the larger numbers to the strata just beneath the surface. Again, where the surface is covered over by a thick sod, the thrips may be generally found among the grasa roots, not deeper than one to three inches. 36197—4 t, : . i ii I r 20 orrhi^Ti'J^p^®^®!' A°u ¥'"° '"i ^?^^' measured samples of soil taken from the orchard at Royal Oak, beneath the trees, were examined reimlartv throuSio^t the summer and autumn from July to NoUmber. Very flw^S were foun, ^l'l\''£Lf ® *°. ^° '"'^^^l t'''^ °°°« ''^ "» '° the 1 Jse s^SfmSch Th soil IS a tenacious clay, and below 10 inches is scarcely penetrable In ihl rumm;r'hv ^t'^"''H*'"''^ by its capacity for retaining mTsture and, n tt summer, by its tendency to bake hard under the heat of the sun. The Prepupa (fig. 5). 0 6W mm; width 0-383 mm 'SW .LSar ta'J.U ,J?i„T'P*''°J" 0-35 mm; length of abdomen brown. Head «ubquadrate7kbout m bm^ J^ln^ ' «''°'"-. t™5»l!'cent white, deeply tinted with rounded, extendinito abSut one^hllf leSThtf^roXnum An^.i:^'*"'^ ^'^'^u """th^"" broadly of head, apparently four-jointed; firet three ^^^^pili„ „,£!^"? ^^f*"!'?* bf^kw*"! on each side thick and unwieldy; segment IV atoutMl^S^reZi^L~^"^ ,"'•»!«*»', about aa broad as lon«, pint Antenn« withTfcw iicoMpJcuo" whftc S S^.t°„«,'' "'"'^'''5* "^^ **^"»« *" »° °^^^ broadly rounded posteriorly. Me3(™ hm^^r- ^U ™5P* u "^ Pf"'^ ^V^ " 'o"* »» the head, to distal edge of third aMomiMf«SS^„t AM^^e^l'S^^^.lJi''"^^^^ gradually tapering from their Mter^vFi^t.?JhfJ^:?^*''\f^' ^"'?** »* "^ "><* IV. segments of IX with b^d spines somewhat siS to h^*f L^'j;!^.'''''''''''. \^^ ^ ^°J^'- dii^J end .tout, s.mil„ to those of full^wn I'^r.^, X^^y'^^ ii^Xi^^^^X^t;^:^:^.]^^ Vig. 5.— The pear thrips, Taeniathript tneoiuequeiu; pupa, first staginning of November, so that the total period covered by the pupal stage lasts for si.x weeks to two months. In certain seasons and under unfavourable conditions, it may extend for a longer time than this, but it is interesting to note that there appears to be a much greater uniformity in the duration of the various phases of the life-historv in Vancouver Island as compared to California. Foster and Jones' state that the earliest pup® are found in the month of May in the Santa Clara valley, but these they consider as developing from premature larvae, the precocity of which has been determined by infection with some fungous organism. Their latest pupte are found in December, with the maximum number appearing in October. This latter month also represents the period of maximum pupation in Vancouver island. ! j '!' i if m !1 22 «♦», ^*,T"'.** ^*^* ''^° reasonable to suppose that pupation would have been I^e'mor?:<;Sabl"'''Z' ^vh' *^" '" '^^*"'°™''^ "'^^^^ ^^^ ^'^"'"^ '-^itbns are more equable. Our evidence, however, goes to prove that such is annar ently not the case, at least not to any marked extent ^^ in the middle of June when the larvte were full-fed ind fRllmo. f,^^ tu^ S'finX x'r rv^^''" "^^^ «pe-aiiy cot^VuctrioJe^^^^^^^^^^ with finely sifted soil. The larvae burrowed beneath the surface iust ^ they would do in the orchard. The boxes were then buried "n the ZLd with thtir tops level with the surface, in the yard adjoining the labSrv tTi. Zlu """"^ *''"' •'^Pf ""^^' «''»««* "'^t"'"' conditions* From time to time small samples were taken from these boxes, and table IV show™ the com 5^IO^oTotmtr'Tr9,r'^ ""' ^^"'^^ ^' "'>^^' ^'^•^ au?n7thfperd- -^' Fig. 7.— The pi-ar -hrips. Taeaiothrips ineimsequenx adult winK.s,mtspipad. ,X9S. (Original). T.VHI.K IV I KNV.rrXv"M'i.LKs"'Rl>^YL'o'V NOVKMHKR. 1«I7 ■ ^'^^'^"^^'^''* '-^LAND, B.C., DURINC; .III.Y To Sample .utnhiTs. I to 8... 9 to 18.. int.>:6. Dates I'xatnini'd. luly 10— Si'pi. 10 Sept. I:J— Oct. 2 I Oct. a— Nov. 3 i I..^KV.t:. N'uiiiImt 32 33 I I'or rent. 100 16 0-7 Pi p.B. Number. Pi>rccnt. 77 Adiltm. Numlx-r. Perfvnt 0 0 84 I 0 .M'8 I 53 0 0 405 The Adult (Fig. 7). 02 mm;wXh'-:f"iurtLl'Sl":'^"'"WidTh'\^^ length of pro. hora. 013 mm; width I^iiKth o( antonnal «r«n. "nt": f 33 « n 45\r 111 M i- ?v il''" v li "T.' '"»"' '"Wh l-2fl mm. total, 0 31 „,„,. Cohmr dark Im.wn tan, I ihi ^2Jni ^ "ii ^' ^'iJ' X'' ■?«."• ^'"' » "• VHI. 12 u: ohe.kHan.h.d.antoriorn.arginan^LT.^.iX./taVirr^^^'L'iria,."^^^^^^^^^^^ ■^--^, 23 f; 1' "^v'i^i'.°iL^J^'^ '""* P™™"«">t "P'™-* >*etween poxterior ocelli. Eyes prominent, oval in outline, black with light borders. coar««ly facetted and pilose. Ocelli approiimate. yellow, marnihed inwardly with orange-brown crescents, the posterior one- approximate to. but not continguous with, light inner borders 1^";^"^"*''^°'* '"V*'^- *'f»*^ *."*' ^^'^^' •""""•'"■y P»Ipi thr«-8egmented; labial palpi Two- segmented, basal *gment very short. Antenme .ight-^^niiiented, alx.ut two and on^half tin^s as long T^-^"" '?™ •'«*». "ceptsegmen III. whirl; is light brown; spines pale; a forked sense-cone Z h TtiH , .1? "r*'"/'"* "'• *'*•? » »""''»[ ""•• "9 ventral side of segment IV. Prothon.s about as long but wider than head: a weak spine at each anterior and two large, strong oney on each wsterior angle- other spines not conspicuous. Mesothorax with sides evenly '.nvex, angles ro mdnj; metanotal pUite with four spines near front edge, inner pair largest. The mesonotal and metan.-.al plates are aintly struite. Legs moderfttely long, uniform brown except tibia; and tarsi, whi.h are yellow. .Spine, on tip ?/„„r.K!l„J^ L.!" ,.' ^'"'^\ '*""^ "P'."'"" "" hind tibi«. Wings present, extending beyond ip of abdomen, about twelve times as long as wide, po^ ,t.^I at tips; cost.* of f .rewings thickly set with from 28 to 33 quite long spines; fore vein with 12 to 15arrangeor 16 regularly pUced spiiw Z^U^yfZ^l""' .T'"""^;;* *"■"''■ *','•*"* »* '■"•"»' ""'"••"■ -^hdomcn subovate. tapcnng ab?upty TO^tive tiiSul "low" ««'"«''«: longest spines on i«-gments 9 and 10: abdomen uniform brown; In comparing the wings of a large number of adults, it is found that there IS a greater variation in the number and disposition of the alar spines than is stated by Foster and Jones in their description above. For instance, the number on the costal vein varies from twenty-three to thirty-two on the fore- vein from twelve to eighteen. An examination of 100 wings showed that 59 per cent had the basal spines of the fore-vein arranged in two groups of three and SIX. The first group of three appears to be stable, but the second varies from four to eight. The spines on the hind vein vary from twelve to eighteen. Duration of adult stage.— The total period of aerial adult activity extends from about two to two and a half months. The numbers increase to a maximum depending on the rapidity with which their emergence from the soil proceeds Gradually a diminution begins until, after eight to ten weeks, only a few stragglers remain on the trees. This season's records show that the adults first began to appear in the last days of March and to disappear at the end of May, a few remaining over into the first days of June. It is doubtful whether these late individuals lay any eggs. At least, none o/ them were observed to oviposit It must be remembered that adults are to be found in the soil for a considerable time previous to their appearance on the trees. Most of the pupse have probably transformed to the imaginal condition in the autumn and early winter. For a period varying from one to five months, with an average of possibly three, they remain inactive in their subterranean cello until conditions are such as to favor their migration to the upper a=-. LONGEV Y OF ADUI-TS IN CAPTIVITY. In captivity and witl .od inside the laboratory, adult thrips do not live longer than four days < average. Among large numbers thus confined individual specimens have !< d as long as eight days and, in one instance, ten days. If supplied with food, .some will live as long as twcntv days, a result which was repeatedly obtained by confining a number of adults in large glass vials with maple buds, their escape being prevente' by a muslin cover which allowed aeration sufficient to obviate the collection of moisture on the walls of the tube. In the field, adults imprisoned in mica-chimneys fixed on the trees lived for as long as four weeks. It may be inferred, therefore, that under natural conditions the duration of the adult's life would probably cuvit a period of about four to six weeks. IS'I ■i:l .W M- ft fy \ t!l 24 'N- TABLE V.-LOx\GEVlTY OF ADLLTS IX TA^s'^'^a^ii^'^S l.ir'"' '^""•^^ ««'ECIMKXS NumlMT (u" Kxperiiiirnt. 1 2 3 4 5 li 8 9. 10 n. 12. NuriitMTof Spipjmons. ^ Datp of DtiN-of Dcuthof 1 onfinpiiipnl i Last Spocimcna. Lenirth of Life of TionKest-livcd iSpocimens in Days. 50 Murc-h 29 April 2 4 30 " 30 3 4 6 10 5 9 S g 43 .« 46 2S 119 116 " 31 " 31 April 1 1 " 2 " 2 6 " 10 (I ;; 10 " li) 23 3 10 76 4 " 11 S6 54 S " 7 " 10 12 5 5 jwlSa^'JdwB case survived fron, April 20'Slay to, a^J^rioTrtSS S"'"' '" '"'''' MIGRATION OF ADILTS FROM THE SOIL TO THE TREE. s.;.iSr;^iqj;i' iir-ffS,,;:^ 5S:: ,:;■ ™r r'^sis, rt,^ with hnlliant sunshine, an air teinnerature of ^2 Zir«l" ir i ' . \^^^'' iBi 25 This may be repeated several times before the animal embarks with a spring from the surface on which it is resting. The legs appear to assif.t in this initial movement of propulsion. As the adults settle after a flight, the wings are immediately tucked in and arranged straight along the abdomen, parallel almost to the mid-dorsal line, the anterior wing of each pair covering the posterior one. That there is an undoubted migration of thrips from one variety of fruit tree to another is well borne out by facts. Thus, swarming from the soil was practically finished by April 12 at a time when the buds of Fluchess, Gravenstein :ind Red Astrachan apples were in a receptive condition. At this date there were practically no thrips (m the King and Wealthy varieties, their buds being as yet tightly closed. Later, as their l)uds open, the migration becomes more evenly distributed throughout a mixed orchard, indicating a migraticm from early to lute varieties. The same phenomenon applies to pears, of which, in the particu- lar orchard under observation, the Bartlett buds are the earliest to open and arc therefore first attacked, followe*»"■ cross slats, 2rches wide bv fivliv^hl 1 »'o«om was re-enforced with thr. tances of 6 inches apaJt Eachtllf wf °^ ^""T} ^-^tP' P'**"^^ «»* ^q"«' -i diameter, which also'^erforatSthtboTt^m'''^^^^^^^ °'" '^ "" fitted with a closely fitting cylinder of Hn ?L fm^i ^^^^ *'?'^' *8^'»- " with a narrow flanite one^iiZh ^f „„ • u ^u*' ^9^' ^* '"'^''^^ d*"*"?- Provid. the hole. Cide Xs cvSf a ?fn n J"'^ '^1°''^' *" fPP"^ the cylind.T , basal margin. The apS Unerture nfTh" "^ ^^' '^™^ '^'^'K*'' ^^^ fi'ted t., r- 27 nullifying the escape of the thrips once they had reached the tul)e8. As well a« bemg an accurate mdex of the period of emergence, the counts obtaineil by the use of these trap-cages represented the actual number of thrips that were present in the two square feet of soil covered by the boxes n^Z The average of the numbers emerging in six boxes throughout the orchard represented roughly the degree of infestation of thrips in the soil. As a method of assistmg the orehardist m his operations, no better plan than these trap- cages could be employed for determining accurately the first appearance of the thrips at the beginning of the season. Necessarily, the boxes mu.st be stoutly mai vials, and fitted into the holes of the soil cmergenre-hoxes, in the orchard at Royal Oak. Vancouver island. X 2. (Original). 1 h 'Ti f ''^^•"■**** apparatus consisting of an inverted, cone-shaped, muslin i)ag (hg. 11), suspended from an overhanging branch, will be found to provide an excellent indication to the orehardist of the first emergence of the thrips. Ihe lower margin is provided with a circular piece of stout iron wire, which serves to keep the bag extended. Sods are placed firmlv around the base m order to keep it in position and to prevent the escape of the insects. The whole apparatus is nothing more or less than an in.sect-coUecting net made of stout, close-meshed muslin. It should be examined every day for the presence of adult thrips, then turned inside out, shaken, and replaced in its former position. Thus the orehardist will obtain a fairly accurate idea of the daily increase or decrea.se in the numbers emerging, and will he enabled to decide the period of maximum emergence. For obtaining efficient results, these traps should be established in the orchards about the middle of March. In table VI is represented the actual numbers of thrips emerging from the 'joil and trapped in each of six boxes distributed through the orchard at Royal Oak, Vancouver island, B.C. It will be readily seen that the largest numbers appeared between the dates of April 2 and April 13. -J' ! M' 4' . ! t 1 i J 28 ^^ \ TABLE VI . ;,- BOXKS PARTLY ANCOUVER ISLAND, 29 EMERGKNCE OF ADILT8 IN HELATION TO TEMPERATIRE. The records for the years 191G and 1917 go to prove that the critical temperatures which determine the emergence of the adults from the soil in the spring, are 45 degrees Fahr. for the soil and 50 degrees Fahr. for the air. Should the temperature at any time fall below these figures after the emergence has aetually commenced, the effect will he to delay the process and to give a double or treble maximum to the curve of emergence. On the other hand, should the temperature Ije maintained above the critical point for some time, a graphical representation of the emergence will show l)ut one maximum. 'i? Fig, 12, — Straight-liiif cun-t- showiiw cmrrKcnrr of aduit p«ar tliiip:, m trap ciwea under trees in onlmrd, Royal Oak. Vancouver island, March 2S-April 25. Dotted cur\-e is a graphical representation of the average daily mean soil temperature during the same perio;i. ((Jrii?inal). It will be observed that the curve of emergence for 1917 at Royal Oak, Vancouver island, B.C. (fig. 12) has three distinct phases, between the dates of March 4 to 10, due to the variations of soil temperature. On March 5, 7, and 9, the emergence was notal)le by reason of the large numbers which deserted the soil when the temperature rose above the ■ . h. i" n 13 m 30 On the whole, thrproc^ wa^ markp.l wif' fal below 45 degreoH Fahr. hen enier«ng in a ?S^ coC^rine JixL/ H «P«d>ty. the greatest num- after whicK tLre waTr^aS aLS nffln^' ^'T ^^''"'^. ^ *« ^pril 13. was completed on Aoril 28 Th„ b'^ * ^° '" n""**". until the emereene,' practicalfy identreaf a faS Jt^^iTZi^JuT'"''^^'^'}?'^^'''^ ^^'^Ven. of the temperature conditToLt thelprin^fnK^ f^.^V'"""'*-^ mean air-temperature between the dates nfM«rnh o^ j \ •?'*' ^^^ averaw of the adults Vmerged, was 49 d^«^ I-vL p Vu """^ "^P"' ^O- *hen most was 49 7 den-ees Fkhr Tk! .. ^^ *"'• •f"'" **>* ««">« Per'"d in 1917 it coveringVh^'^^'Sme wlre*^ r^Siveinsl'd^Sr^^H^^ ^ }«'« -' '»'^ Fahr. It is likely that the e^J^ZlLiafJTu^' ^"^J^f^ « 5 degree, kept, would have proved to have [w. ZJ ' •?'ll" "° '**''"'*•' ^Kures wen- owing to the two deSL hi«h?r vip« """^ *-^''" ^^'^ ^^^ <"^ '«>■ »917 abnormally highTaiSKd sno^dl ZlL"?hr «}''-»«™P?^«t"re- Only. th. might have offset the teSrS «Hvfn?f„ k "'^ '?°"*'>'' "' **»«' y^«r »9>yr(l bli)n«)iii-bu(l and an injurnl l)li»woin-clu.ft«"cl by thr (cfMiinn activities of tin- adult ppar thrip.-<. (OriKinal). * pit has been fully demonstrated that the species can succes.sfully complete its life-history on the broad-leaved maple, the June berry, choke cherry, and Xuttall's cherry, causing damaRc ex.-utly , .'rallel to that "which it commits on deciduous fruit trees. There is no evui. ; > , however, of its breeding on the others just enumerated. In 1917. ti e injury to maples was greater than that caused to any kind of deciduous fruit (rr •>. and was widely distribute«rt H: fieant that the insect hc^ K fo^mH '^ S'" TA" *" ''"^^^ orchard. Likewi.se, w.^ found o be ZrT^^"" ^^ "''"^ ^'^f^"* f--"'" ^"' the gulf islands, both inlani and a L^re s^Xor^ofr '\ """''^^ '"'^'''^'^ ' fruit trees, and sometimes senari nH fr!.L k .' ", '" ^'*'^'"^' "lere were 11. timbers. separated from orchards by thick shrub and tOl 33 Susceptibility or Fruit Trees to Attack and Injury by Adults and Larv,b. So far as one can judge the relative susceptibility of the different cultivated fruit trees to the effects of the thrips depredations, the palm must be granted to pears among the pome fruits and to prunes and plums among the drupaceous varieties. On the whole, it is probable that the latter, bv reason of their smaller and mo..- >nder buds, ultimately suffer greater damage than the species and var- <:<•> ,.; rhe .?r;ngeneric Pyrus. It might be well to set forth in detail the var (Lis species ol <;ul ivated trees attacked. TABLK VIII -CULTIVATED FOOD-PLANTS OF THE PEAR THRIPS. Family. Rosacrs. .luKlanilapite. Genus. PyrtM. . Cydonia Prunm. Juglan^ Species . Common Namea. communis L maluH L rut^jaria Pers (irtum L, vara. ... domi'Htica L, varn. , dumeMtica L, vars. innililia L. vara. . amygdiilim Hook (irmeninca L Perxiea Benth regia L Pear. . . . Apple Quince. . CheiT>' Plum... Prune Damson . Almond. .\prieot . . Peach . . Walnut... Nature of Fruit. Pome. (( *t Drupe. (I Form of drupe Some of these species are not grown on a commercial scale on Vancouver island, and for this reason the damson, almond, apricot, peach and walnut may be eliminated from our considerations. They are, nevertheless, with the exception of the walnut, recorded among the principal food-plants of the pear thrips in California'. Should the pear thrips by any chance be found in the future to assume economic importance on the mainland of British Columbia, the apricot and peach, at least, which are quite extensively grown there, will probably suffer seriously from its attacks. jr . 1 DAMAGE TO PEARS. The damaged buds of pears are the first to arrest attention in the spring, (ng. 15, A). Working their way in between the opening scales, the adults begin to feed on the tender parts within. As a consequence, the buds begin to "bleed," exuding a sugary sap which crystallizes by evaporation on the exterior of the bud, imparting to it a dull glistening appearance. Where a number of indi- viduals are working on the same bud, it fails to swell and assumes a shrivelled, ' scorched " appearance, characteristic of intense infestation. Whole trees may be thus affected. In time the injured buds are attacked by the spores of blue moulds which cause them to turn a bluish-black colour. Some buds will contrive t() expand and send forth weakened blossoms in spite of apparent serious injury. The ingress of the mould .sp,ii,« i,,, however, an effectual check to further development. Toll is levied on all the tender parts within the bud, leaves and their petioles, blossom stems, the developing ovaries, and stamens with their anthers. I 34 ii. m I'll Hi Si 35 Thf fiama^p throughout a poar orchard is not always bv any means uni- form. It IS ofton diffirult to tcndf-r a satisfartorv explanation why, of two trees of the same variety situated side by side, one "will have praetically all its bud« rumed whilst the other will set a fair amount of fruit. The same phenom- enon ha.^ &lm Ix-en observed in the case of two adjacent rows of trees of the .same vanety. In the orchard at Royal Oak, an isolated pear tree of the >heIdon vanety surrounded by Hart let t and Rivers' Princess pear^ was so extensively damaged m the bud stage that, throughout the season oi 1916 it contra.sted quite strongly with its less stricken neighbours. The only reason which can be a-ssjgned for its poor showing is that it develops slightlv earlier than the other varieties, and the adults had committed irreparable damage to the buds before attention was called to its condition and a treatment applied More significant even than this ca.se was that of a Duchess of Angouleme pear grafted upon the variety Rivers' Princess. The graft is a .somewhat earlier hudding variety than the stock, and the time of .swelling of its buds coincided approximately with the maximum emergence of the adults from the soil. It thus laid Itself peculiarly open to attack when the closed buds of the stock were as yet tightly closed and protected from injury. In one tree the graft, constituting about one-fourth of thf foliage, had its buds almost completely destroyed in •ided contrast to those of the stock which had made comparatively good )wth. One IS thus forced to conclude that, .so far as the pear thrips is con- decid grow ceme insecticide will not on pest on both variitics. infested bv adults; but season. Further, one and the .same application of an this account prove equally efficient in controlling the Pears of the Bartlett and Bosc were (piite heavily the timely application of sprav solutions reduced the early injury to a minimum. Louise Bonne, F'lemish Beauty, and Rivers' Princess, by reason of their later ilevelopment, did not suffer "materially It must be remembered that the number of adults in a bud is not always a reliable iTiterion ot the damage that is likely to accrue. Ten or twenty adults attacking a young opening bud will often do more to check its future development com- • v than fifty of the >pecies working in a i)ud which has made greater and JMconie strengthened by reason of its growth, rnea.-ures should be vigorously carried out; tor the more that will persist to lay eggs. grci Nevertheless, , , , inexorable the ti ....nt. the f.wer the a that will persist to lav eggs, harbingers of ilamage to come. Nor must a truce be called because' the miinbers of the adults may be dimi:.i-hing. Xo matter how carefully the trees of an orchard may be sprayed. th< r.- will always be a goodly iiuiiiber of adults which will escape nemesis. Therefore, one must be pre|)ared to make an additional treat- ment against th<' larva' which hatch from the eggs laid by these adults. In this way a crop which may at first appear to be a coniph'te failure, may finally yield a respectable return and amply repay the owner for the labour expended. With an insect so insidious as the pe.ir tlirijis there <'an be no relaxaticm of (me's efforts. Half-hearted measures an> likely to prove more expensive than none at all. -A.- to the l>est time for applying insecticides, no hard and fu.st rules can be drawn up. Seasonal differences may cause an early or late appearance of the thrips, according as the conditions are favourable or otherwise. Under the circumstances, the orchardist must rely to a great extent on his own judgment and decide for himself. There can be no doul)t, however, that once the thrips has reached the buds, control measures catm"t be undertaken too .soon. nA.M.*(iE TO .API'LKS. On the whole, apples do not seem to l)e so susceptible to injury as pears. The buds are more robust an f^r Ii^' " >•! ** "* '*"'• Feedmg on the young fruit also quite oommrcm isitVZrs'"^" '^'.''I'r, ''"P"''^'-'^ known as 'IJIb '• trees „n whioh adult ^ S'C.rf, ■ ^^ 7"^''* '''" ^''P'^''^''''' t^ose untreat..! Krcutest larval injury ttluhliXv" I '"■'•' "TT""''' ^''" "''Perience th.- fruit to the loaves, where thev m vT.o ?» "IT'T "^ !''e™Pa«s from the youn^ Pr.ncipal veins. The lo"utLe'';L':^J;:!n"1.X"p'i.rtt;d ^'" '""^"" -^"^^ *' ^ pediee"sli7]6).^'''^*''*'""'' """'"'»"« ^'KK-^-ars will he foun.l on the young fruit 37 DAMAGE TO PRUNES. The destruction of a prune crop ))>- the pear thrips proceeds with great rapidity after its inception, and, taking tree by tree, the damage is as great as if not greater than that caused to pears. For ten years there has not been suffi- cient return from either the prune or plum crop in Vancouver Island to repav the labour of cultivation. As soon as the adults emerge frop- the soil, thev may be seen on the outside of the buds impatient in their efforts to effect an entrance Once msxle, they soon make their presence felt by destroving the most tender parts. As the bud .scales arc forced apart, the young leaves and blossoms instead of being fresh an of pcir thrios -Muy 31, 1917. {Orminal). ;iti(l at't.T they have opened. Year after vear the iirospects for a licavv croi) imiy appear bright and rosy, only to be reFX'atediv blasted l.v the dejjredations "t the pest. It is our conviction that the spray .soimions appliful at Hoyal Oak this year would have accomplished much towards saving the croi) of" Italian prunes, but unfortunately the occurrence of two sharj) attacks of frost on May " iind 12 blighted our expectations and entirely negatived the r»"sults. Plums of the Pond's Seedling and Columbia varieties were not so heavily infested as the Italian prunes. It is rather a disheartening si)ectacle to enter an orchard and see the prune trees presenting a scorched appearance, with an isolated blossom here and there reminding one of the departed glorv of the crop. In l)runcs and plums the scabbing of the fruit caused by the feeding activities of the larvae may seriously depreciate its market value, if it does not indeed render It quite unsaleable. Were persuasion necessary, nothing couhl be more stimu- lating to an energetic campaign of combating the thrips than this story of prune destruction in the Saanich peninsula. As has been previouslv mentioned, the deposition of eggs in the fruit petioles and their con-sequent weakening may also account ,or quite heavy losses in prunes and plums. DAMAGE TO CHEKKIES. Although cherries are severely attacked by adults, they generally set quite a heavy crop of fruit by reason of their comparatively large product- iveness. The thrips first begin to appear in numbers as the buds open up ; - if i ■ <■ II if i ft ;■ f tity i' *? ^ II r.:' 38 or to .„„,.. oxtont. ,1... .^ •«• rs norfcwH '':""« ""i'"^ l>u.l-rl„Mtor.s ; Oiik in ,1,,. spring of Um it was our rivil .«* * i "'"^ "^ '^''P- ^^ «">"! Ih' th.« thrips ,lania». t(. -h.^HL J •'^ to ohwrvo how intrnsiv.- iniRhi .ypross-lik,. appoaran,-,.. In .!» ni« s .^.ir " ""r* ^"'•'""' '""' ;;. pusl. out thoir l.losso„.s anVl^v/Zu^r iaS;v'"''lKT.r.'";' T*"""' had luvn s.-cniinRly arrested owinir nri'snm ^^1. . \i "."^ .'" '••'Vflopmcnl The elus,,.rs ha.l first l.r.m-^e land then h S.. ". 'rr''^'*"'" "^ ""' '"'"'«■- to the hranehes durinij the winter ,1 M«rfi l'"''.'- , "^'"'J' ■'•'niained attaehe.l irrxt-daSiS^^ «. .. .itth. e. • e ror not^^^tll ^Z t^^Xrll'lSS/-^^^^^^^^ the iff^^iiiiuiS:: ~;Jn;;il;;;xi::;rK.i""'^ ^f^y v -'""-- mumnv a similar eon.lition s?nL from the rnni "." ','"■ ''"* •'"'• """' '"'«'" iunouKst the foliage. Ti.is se.Sarv ^Hm„i. '^''P™*.'''' «'<•'' very of small sh,,, for a de,i,i,..l redu,-ti,,n f the Is^^^^^^^^ ' V""*'' T'r^'"'^' '""' r.-sponsil.].. 1>.' rather detrin.ental to tlu. gro~te "^ "'" ''"'^'"''- ^^'"''' "'"^' i inst^riVin'TonSVIr'Si:: "'">• -'"- ^o ^he young fruit was ele.h Olivt ""•'".'Vf'- i.slund. (hi Mav 31 1<)1 "^ •"" "-":..Ts of larv. thiu'r ;i.'L.ii;^^i;ja;r:;;e;rr • '•' REPRODUCTION. OviPOSITION. arises];;^fc!;SJ«^;,iSt;;'a,i:}o„Sf ^^T '^J'r^^ eharacteristi... , for its reception by ,iri?Z?at "„ of ^h '"'T" ' •?'^."'^^ '" « K'-""^"^ -I'lrP' segments. Four distinct StoTSer^ilf' u?*/'*' ^^^'T-*«« "^ Jhe two ultin, , pair originating from the eighth and the ..nn "P^T'^!""' ^^'^ '"^" «"''" abdominal segment, ('urvfng Wry ^JntuP'^rr.'""^"."": P'^"'" ^'•°"' ^^'' >'i^ on the uprn-r mIk*- of the ower plates, the apparatus is rendered more tensile «h.le at the same time allowing of a certain degree of sliding pfavTthe uppe; plates on the lower. Lxeept when actually in use, the oviJosUor L hffn ,1. Its receptacle, a ventral excavation of the two last segments. lorminal. abdominal sei{mpnt!.,rf adult to show the ovipositor. X l.W. (f)ri«inBl). The actual time taken by the female in laying an egg varies from two to three minutes Sometimes the ex.serted ovipJsitor is ensheathed too leen v ,n the plant tissue,_and the in.sect experiences much diffi.-nltv n IV^S^ .. the plant tissue,_and the in.sect experiences much difficulty in extricating Fir. 20.— Transversp swtion in outline of fruit-stom of Italian prune to show CKR-i'haiiiher!! in the outer laver of rell,« feorlex) Drawn from actual Hpn-imen. e. epiderm: c. rortex- rr ehlorophyll layer of rortei; e. h. hair; p. r. egg-f'hamber.' f. r. />, fibriVVRseular Ijumllra; m. pith. Xlti. Ulriginal;. It. On one occasion an individual oh.served ovipositing in the stipulate leaf ''t a King apple, was engage-: for about thirty minutes in trving to withdraw Its ovipositor before success atteniled its efforts. Numerous cases were recorded '-t the ovipositor being so .securely embedded that the insect was effectivelv held prisoner and finally succumbed. " I- • f ;!• - t : ; i , i'l ^0 m lu at H«ht angle, to th^e 'H^V-'Arp^ A^Xre^t^^^^^^^^^^^^ I! ''''Y*!'^*'"'" '"J^^Ml'aeieL^.-j..- ' in Si,J'mof'„Vpl.-.'^vi^if^ •^•^-'l '•? "'- "'t -f ovipositing f i>auo. X 126, (OriirinLn; ""hMl'IfHl and r..prr8 Mt...! as evi.i<.nt in tl... pl,,nV it.s mouth vlHsVm.rTh "T"^ '•'•■" *" ''"•^'••' »ho .'pi.lerm first wr !ii< 41 very rarely einbe I'lossoms, in the district of Lve.sham Worcestershire. The spe.imen was collected bv u ■ 1.5 ^'T' f".':'"'''"'>' 'i th*- ("o-Pcr Kesearch Laboratory, Berkhamstea.i. Bagnall' to whom it was submitted, briefly described it jis being much smaller than the female, with wings consi.l.Tably over-reaching the tij) of the abdomen. Such a description is evidently rather inadequate. In the absence of males, the normal method of reproduction is partheno- Kenetic but there is no altcrnution of generations such as prevails among the Aphididap, the gall-formmg Cynipiche, and some Tenthre. Tiie signi- hcance of the phenomenon is that it secures for the species prolific multii)lication Inhke the parthenogenetic species of Phasmi;la> ami Aphic ,,i the subject in the pages that follow. Spray mixtures consisting of miscible oil No. 2, or whale-oil soap and nicotine as controlling agencies. The jjrovision necessary, to a gr(at extent on the timely , . , Therefore, in regard to this insect, and probably inore .so than with many other important orchard i)csts, it is advisable that the growers should make them.selves well accpiainted with the form and habits of the thrips so as to decide for themselves the correct time for spraving. It is unsatis- factory to state in other than general terms the approxiniati' dates for applying the spray, inasmuch as no two seasons are ab.solutely similar in respect to climatic conditions. Further, it would appear that there mav be from year to year a decided variation in the degree of infestation affecting' the same variety of tree. In view of these facts, it will be readily observed that a great deal depends upon the carefulness and skill of individual growers, and it cannot be too frequently emphasized that the essential features of the life-history of this insect must be clearly understood before control measures can be intelligently undertaken. I f i i H II- ! I 4a It w„ul,l only H,.rv.. to l.^sse„VK|^ 7thi" ImH IJin"" 1 " "'"""•V '"*"'" "'•*'''"•^• iin|H.rtant |.„inf« «r.> pn-s,.,,t''.l. '"••Iu'I'hJ here. Thcrrfcr.., „nly the moHt SPRAY MIXTUREH. the W lS"Sh:r":;S'i';^Kj;n'\^ treatment was n,a.le against first revoale,!. In l«l« a tot^l « 1 vj.frni .r '^"TTX "^ *•>:' ""•^'- '''"P^ *«« over an area <,f 138 aeres, «i^ iav: hv flrn! "^ ''''^T?' ''?''''• '''"tHI.ute,! 1917, a similar .ampaiim of «nr«Lv"L ul, •'^*" *".•' '"*"'' nmehin..«. hi Moeks of trees were'St." K't ^e^ffi'irj"'/*"- • '" '•"''' ■"••*«""« '<""'» mixtures an.l the numln-r of Irav Inii-^^ ' ''""""'' "*"'"«» hs «f sprav- results. ()„r work. thn.uUout w,L?rS^^^^^ neeessary to ensure the In-st obtained against the peTZCTJhfn^^l ■ f."'' ^'"i"** ''^ '»>- ''•'•""'♦« The inse,.tiei,les ehiefly emploml duri^" thpri" ''"'* ^"^ ^"^'^ «t«t-'- mixtures .-ontaininR either whaler,! "nan or mf • /'^"■■'T""'* consisted of t.on with nieotineM.lphateand^;:trTs'l?[i,„^;;^^^^^^ "'' ^-- 2 in eombina- MisriBLE Oil No. 2. insecScJ:' •!i;;t:ir'Z:T2ic:;J,;''iirtf*«»'- »»>.. use of miselhh. oil in province. It was un.Ierstoo , h Ve J^v^ " '*™""*5. ^^'' ^""tRrowers of this of the pear thrips in ("Sn a an/K S^^^^ \ ork state. Information wius rt^eived from S'^'^i- f*^""™''''" ^P""*" '" ^^'^• cultural Experiment Station, CorvallTs oZ"' fhn! I""' ^"™'''"'y "^ ^^'^ Agri- dcRr. '» offset the value of later sprasannlilJ.f'''' ""^lu^'" ^PP^'^'"'^ i" «ome 'nrhc, ..S-, a fungous disea.se affect.nriunn whi.h ""• ""^^™''"«?^' ^"^eofabraea the ru..>t serious in the northwest coital i^nH r '« universally regarded as datec .Mav 10 iQis he Vlrni/f** t- '^^V""*' of the Pac fie. ]„ a letter wcvuld say that we'ha'; rt^lCe^"; sSt ' V.^'^'r ^ " ^'^»> ^'^'^'^ '- «*' I following the oil spravs, appSo s f iLf T u ''•'"' °„'""K *" ^^^ f"''* th^t, the trees in the fall for' anXacnose' wiH VZ " ?^"' °' Bordeaux delivered on one may have a complicatiTwhLr Sr?ot'?V'''''-^J!^ ^«' ^'''^ '•'''^»" measure..' Furthermore, we arHnd j'ted to 4 W *" p '^.'^*' ^/"^^^^^ Chemical Company, of San Francisco Can^ i i* '^ ^°1*? °' ^^"^ ^^-n^ral drawing our attention to the possHjUitv nf f h/ "•"'" ^«t«'/pril 30, 1915, for following the application ofmSfe S L 2 To'n.?T t^^^^^^l^" '"Jury care is requ red in the use of oil «,.L, . '^° 1"*^**^ '"'^ words: " More pear tree.:* The folfage Is te TX Z^E^" 'T f'' •''«°™'"« *'^«« "' -njury. Varieties differ somewhat fn this rejLdZ.t In ^' ""f," ^"^'^^PtiWe to ible than pears and prunes." Dr E P Fett" ji i*^" "'^ "^^''^ '""'•«' «»««^''Pt- 2. Is effects on various kinds of fruit trees ^ With tSrv^JnWSelEc^t^ ""'• »-d-- •»-»"-. their composition varying accordTngt? the tr^'V" "^™'«Si'>^«• oil were tested, administered at the time when the1,uds were ^fr°/ ''PP'^'^^.V""- For the fiis,. toevery 200 gallons of the mixture.* »>ursting, 5 gallons of oil were used l! 43 For the second and third applications the quantity of oil was reduced to 3 and 2 gallons respectively. In come cases, four treattti. 's were made, and the amount of oil used for the fourth was two gallons a^i in the third. Several tests were made at different times before the period of blossoming and after, and the results obtained may be briefly stated as follows. It was found that miscible oil possessed great penetrative power and that buds, even though partially closed, would gradually imbibe the oil beneath their scales wil telling effect on the thrips feeding within. This characteristic quality of oil is undoubtedly a great asset for a spraying compound to possess, especially in the section where the work has been carried on, because the months of March and April are usually attended by a slow development of bud growth. As to the killing-power of miscible oil, there is no doubt whatever that death is almost instantaneous for those thrips which are touched directly by particles of the mixture. It has been demonstrated that at a strength greater than 2 gallons to 200 of the mixture " burning " may result, « natr to leaves and fruit was espe- cially noticeable in the Duchess variety. It w;i- observetl that the hairs of the leavts assumed a brow, appearance and shrivelled up. Their function, which is lo regulate transpirativn, is thus interfered with. The epiderm, too, and the underlying parenchyma are also affected. In none of the cases, however, under observation, could the burning be termed severe, except in one instance where the tree partially shed its leaves. \o specific reason could be advanced in expla- nation of this occurrence, inasmuch as other trees of the same variety, sprayed on the same day in another section with th' same mixture, were not apparently affected at the time of treatment or on the days succeeding. Apart from a temporary retardation in the gron-th of the more seriously affected trees no permanent injury resulted. In the less severe cases the leaves seemed to revive and resumed their normal healthy appearance. Efforts were made to determine whether miscible oil caused injury to the trees and their fruit not only in the same year as the app'ioation was made but also in the year following. Apart from the set-back to certain trees in the few days immediately following spraying, no sign of injury resulting from oil was apparent either during the sea.son when it was applied or at any time in the succeeding year. This was true in every case, whether the trees received one, two, three or four applications of misciblr oil in the strengths before mentioned. It is customary in the autumn of each year to recommend orchardists on the coast sections of British Columbia to apply Bordeaux mixture to combat the effects of the apple tree aiithracuose, Xeofabraea malicorlicis. Applications of Bordeaux mixture were accordingly made to certain trees to test whether or not the earlier one of oil would interfere with its effectiveness. In the following spring an examination of the trees thus treated was made with the result that evidence was obtained that the oil did not in any way interfere with the efficiicy of the Bordeaux. In the same way, it may be said with a greater degree of confidence that the oil applications did not nullify the virtue of lime-sulphur sprays in its control of apple scab. Consequently, it is safe to assert that provided in the first application of oil \ 'a the buds are breaking not more than 5 gallons to the 200 are used, and the streni^ius are reduced to 3 and 2 gallons in the mixtures administered when the blossoms are showing pink and after blos.soniiug respectively, no damage «nll result. Furtherm re, its killing-power against thrips is undeniable. Also, no after-effects of an injurious nature to the tree itself nor interference with the value of later sprays have been observed. Whale-oil Soap. Whale-oil soap has been used for many years in the orchards of British Columbia and on Vancouver island in particular to combat various inect pests. In our experiments we had in view the idea of testing: — II J 1 44 1. It« ..ffjMt in .ontrollinK thripn; to 200 gallons .rf water iT^.^Sril^r*' ,"* *'"" "»*" "' '» PoundTof Hoap »um ., r „f treatment. an.J t the ;rt«tT7.f i '"r•'^•'^ vari«l i„ nTjard to ih^ , It waM foun.l that whaleSi Jlln .v'l. ?i'*;"'''" "P"'''V* "' »''" <^«' In many instances. o^p,-riMy^V^rT7- ^^t'^'^^y t.viH. of l,ud, the deKree^c^f"*":;,'^';„;i" "i':'' " ''»'[ tree, whieh have « W however, it ranks hut -■^'eoml n this L^^ ."''"w™'*'*"- ^n •"'•niparison with oTi J-nce to the first appiieaf b „ "• -DTTn' 1 1 ^^ "'■^""'*"•»''''^.v »'«« this r efer- fairly tightly ehilkl. I " Tater T« ? 'T" *^*' ''"'''' "^ "»"•>• varieties an- opened and the leaves have Kn t7.w^^^^ made af„.r the K hav-e of the two sprays are m.t so a^aTnt " '""' *'"' •'"^♦'"'"t wetting qualitiel in the ma Sr; m' Xr;'th;"i;i"\"'- "^'T "' •'"• -P -- very rapi.l o'l It was not quite .,, ,,ui?k7n H X n' TT ;''"•'">• »'it. As ronrpar™' proved eminently satisfactory. '*' ''"* ^'"'" >" P'-««tiettl »tand,H,int it Nicotine Sili-iiate. JO.) »fXly»S3T,l\t„°S^^^^ <"■•"■;'■ ' ™.k-i.., 1 pint of nifotine sulphate to t he 9(mi „ li *"■ ■"*""'•• I" t»'e ,ase of the oM amount of the soap Lxtur!^ ^"" '^""""'^ ^''■^ "-'- """« •* Pints to the . lam.: |s merea.se,l very greatlv. In each eL^. '"7""" '"J!''""'* ♦'"''^ effeetivn, .' ^ ■n-'^eot and finally .au.se. its "uffo, Lion * '^'\ "'•'" " fi'"' whieh surrounds t|,. properties of the basic- const iuenLftW ^St^' "n "''^'r'"* "»*1 «P'-''«'l "^ LiME-Sl LPHIH. tho ...ri^el^- 'ys!:5;"^EE^' ♦»><' rr"V'- ♦•• »- --tiai i,. spring ,t seemed desirable to est *« '"'"'" ■''''P'*' *"' P'^ar seal, in tl hnd whether or not it could be uTed as a^X'' T'""' ^^'^ '«'«'• t^rips, and . Experiments, therefore, were carried cfu^Urthis If '" ''"^ "" "■• '^"^P ''Pra- In every mstance it was ^h^Ji.„\\ \ ■} ""* **"" '» view, penetrative 'qualities It was foun. t I' P"'''*"Tr^ """•• ^■•'"ing and inferior when .t was delivered undeTcoSe Ll "e pr^sX an l"' ''"*'•"-"*"« '^'-'^"^^' the spray. The results aga"nstlarv» ^"^'^ ^'"'" *^*' deleterious effect , f,^ P«P^«Prea.ling quaS^of ? . rmw[urrT/''''t<'/°'-y' ^^' here aga stated m table X on page 49 it is onlvT '^•'t/afted from its value 'on IS slight, and where a spVlf "Svin^S^t'' ^"'" "'^^ ^'^^^^ the Tnfes,- - the expense. ' "'*' sprajmg with o,| or soap would not warrair been ap'plSt'^ertab ■tUrdsru'nVt"''! '™^-^"'^»'- »>- ^^r manv veu- that the non-reduction of their number^ 'l" ■'^t^"'"l'>' '"^^^t^d ^y thrips^ u sulphur to effect a suitable contlol '''"■'-' "'"^^^ *»•« •""'"'ity of liml ' ^ Arsenate or Lead. s^^T^'>''''^y^siiss;V:L,^''ih •"•'^"^ i »■' •■" under rertain atmospheric condition, 7b. „ i ■ '. "»»"iered pciblc lit,. S i^Bi 4S of the foiiagp. fjelipvfe from this tau^. did wcur on one ot'casitm in our experiinent8, but no (lermanent damage re:«ulted. Provided the arsenate of lead is mixed in told wati-r and added directly to the tank, and prf>vided that the strength din's not exceed 2 |>ounds or 2i |Mjunda to the 40 gallons of the mixture, it is Ix-lieved to be quite safe to use in combination with either miscible oil or whale-oil soup under the conditions prevailing in the coa-^tal sections of British Columbia. RESULTS OF SPR.WIXd. NIethod of KEcoRDi.\(i Kesilts. A count of the adult thrips present on the trees wji-s made immitliately {(receding the application of the spraying mixture. The average number in i>u(Ls and blossom.* or on leaves wa.s consideretl sufficient to indicate, as nearly as (jne could judge, t':ie degree of infestation. Buds and blos.soms were dis- -ccted by means of a sharp scal|)el and the number of thrips both inside and outside. Wiis carefully recorded. After an interval of 1 to 24 hours had elapsed following the application of the insecticide, a further count was made. A com- parison of the figures thus obtained indicatetl to what extent the spraying mixtu'e had l>een effective in controlling the pest. It will Im- readily under- '* that in dealing with an actively motile organism this plan of recording 's has its defects, and the experimental error is likely to be ('(msiderable. this reason it is not deemed advisable to present in extended series tabular •videnct- of the percentage mortality of adults and hirvse. Suffice it to say that the remarks on the preceding pages, under the headiriKs of the different inse<'ticidcs, have lK>en ba.sed u|K)n the interpretation of actual ligures obtained in the course of extensive experimentation. The force necessary for the thorough application of the spraying mixture .sweeps large numbers of thrips from the trees, and it is thus impossible to obtain comparative figures that are absolutely reliable. Ii> . rder to determine what happens to those imlividuals thus swept away. chee>f I >th sheets were spread InMieath the trees during the progress of the spraying. On examination of the sheets it was shown that the individuals which had fallen from the sprayed trees were undoubtedly killnl. Thi> meth*Ml of rectifying the error of probability, however. — the best that could be devised — was much too crude to provide results that could in anv wi.». be considered exact. With all due allowance for these difficulties, it can be safely a.s.serted that the percentage mortality among adults caused by oil was 71 for each spraying, ami for soap 68'i. With oil. the larvie suffered a i)ercentage mortality of 85-3 as compared to 84 with soap. The V.\lve of Two asd Four Spkayinos Betohe Blossoming. Some large Gravenstein apple trees were .selected for two treatments with miscible oil— nicotine solution on April 3 and 28 respectively, and an equal number of the same variety was sprayed four times, on March 29, April 3, 12, and 28. After sufficient time had b'een allowed for the majority of the eggs of the thrips to hatch, these trees were carefully examined in May. The results expressed in terms of 100 calyces and leaves, are rendered as follows: — TABLE VIII.-GRAVEXSTEIN .\PPLE TREES. SPRAYED TWICE AND FOUR TIMES RESPECTIVELY WITH MISCIHLE OIL No. 2 IN CO.MBIN.VTION WITH NICOTINE .SULPH.VTK. Number of Treatments. AVIRAOE NCMBIR OF ThRIFS FIR 100 CAtrrlH AfTlR TRmATMENT. -VvERAGi; Nl'HBER OF TuRIFS FIR 100 LlAVU AFTER TrEATHENT. .\dult9. Ijjrvje. Adults. LarviB. 0 2 4 16 4 10 341 ira 44 0 0 0 132 1 1 1" I . j If i f i 1 -, { II • ( ^i . 40 ThK V..CE OK EaBLV .so L.TK APPUC.TXONS. Ihe results were recorded as follows >- ^ ^ ""'^ ^^''t'on 3 on April AND 28: (2). ON APRIL 3;^. ON A^I* ^'^ °~ ^«^^ « Section. Treatment. ' Sprayed. Control. Average Number of I-rve per 100 Calyce. Alter Spraying. Average Number of I^rvje per 100 Leave. After Spraying. Percentage Mortality. Sprayed. Control.. Sprayed. Control. 7i-5 Hi wit^^^'X^ *'''''^' contrary to what tiJif^u'^ Pestsand diseases in genertl contrLioti "^ * l^^' number of Iwvte fn t h? ^•- ^"* *o»'d naturally ™P?«?i^^*'' therefore, to obviate thp^ha ^ "i"""* **>« reason of flight It i* KiigiDie. ihe figures as given, howevpr -^ if *u "'" ''""''' •» consider.^ an 47 BuoDtNO Charactehistics of Trees. The gradual growth and development of prunes, apples, and cherries, from the swelling of the buds to the opening of the blossoms, varies considerably in different varieties of fruit trees. The low temperatures which prevail in the early days of the spring, tend to retard the development of the buds. This fact more than any other interferes with the ready control of the thrips. Emergence of adults from the soil takes place from towards the end of March to the middle of April, at a time when the buds of the majority of fruit trees are commencing to burst. The early spring is often accompanied by cold winds and rains. The adults, therefore, which have emerged, are forced to penetrate beneath the imbricated scales of the buds for protection and warmth. Feeding takes place within the bud, and the adults seem disinclined to move very far. When a bright warm day is encountered, the thrips at once assume great activity. However, it has been observed in the respective spring seasons of 1916 and 1917 that a great deal of damage takes place during these cold backward days after the first development of the buds has commenced. The whole crop might be entirely ruined in three or four days of such weather, and this is especially liable to happen with pears. Consequently, it is essential that growers should fully realize this danger and prepare themselves accord- ingly. They must be careful to note the first appearance of the adults in the spring, and must differentiate between early and late varieties of trees. As has abeady been remarked, the early bursting buds are most liable to attack in the spring and they should therefore receive the first attention. As a guide to orchardists of Vancouver island, the facts regarding the develop- mental phases of different varieties of fruit trees have been tabulated as follows: — TABLE IX.— BUD AND BLOSSOM DEVELOPMENT OF FRUIT TREES IN THE SAANICH PENINSULA. VANCOUVER ISLAND, B.C., IN 1918. Crop and Variety. Dati. Buds Bunting. Buds well Open. Trees in full Bloom. P'nn— Kieffer Bartlett Flemish Beauty Bosc Louise Bonne Boussock Jules Gnyot Rivers' Prinoess Applet — Red Astracban Duchess Gravenstein King Re^*^- *°*"*'^ "' '"« 8« -i' of the thrips in ploughed Sards 7h^n ^i'n fh ""'"^\*°/""*' emergence unploughed The theoiv that Dlmi^hini^ T ^^T °'"«''>ards which are left i«not.a?all.ound,b?c2SotcTntf ^"rXte "'/'^^ T''' requisite to destroy the cells in which ihnZ Ko,"f the fineness of condition the adulto are m^relv waitini^ for Tha rT, ^ i "^ " ^^'^ ^^^ ^^ter. Further and the readier^nXS^^f lVa\mT&tr Int'S^^ °t^ ^^^ ''P": requirement. It may be that the marJ^ll^iA Ploughed soil supplies thi^< disturbed soil is of indiV^t advantwe tofh'^'l^T^T'l"? °1 *•"« •°«««'*« '''on. reaches a climax muchTore ST and o»ri"**f '" .^''** ^'^^ '^^^^^ quickly where the necessarT^recSns are taken H^^" ^ '?!!*"'"^'^ "«^" .« careful examination comLU S "aSt? of actbn ' "*''''"' *••' ^''*''»>*»^'' Schedule or Applicat'ons. dra^"up*ttlLw?rthTsJra?^^^^^^^^ tPP«-«ons has ben, Vancouver island.— sP™y>ng of orchards of the Saanich peninsula of 49 TABLE X.— SPRAYING CALENDAR FOR THE GUIDANCE OF ORCHARDISTS COMBATING THE FEAR THBIP8 ON VANCOUVER ISLAND. Number and Times to Spny . Mixture for Severe Infestation. Mixture tor Light Infestation. I«( SprttK adult thripi in numbers on or in the blossom buds, buds burstins, about April 3-fl. Miscible oU No. 2. S gals, nicotine^ulphate, 1 pt. Water, 200 sals. Whaleoil soap. 10 lbs. nicotine-sulphate, 1) pts. Water, 200 gals. Miscible oil,°5 gals, nicotine-sulphate, 1 pt. Water, 200 gals. tnd SpnK adult thrips in numbers on the trees about a week before blos- soms appear, about April 2»-Hay 1. Whal^oil soap, 10 lbs. nieotineHnilphate, li pts. Arsenate of lewl, 8 lbs. Water, 200 gals. Miscible^oU No. 2, 2 gals. nicotiiie.«ulphate, 1 pt. .Arsenate of lead, 8 lbs. Water, 200 gals. Lime-sulphur, 5 gals.-4 gals.* nicotine-sulphate, li pts. Arsenate of lead, 8 bs. Water, 200 gsls. Srd Spray; larve in the cal>i cups and on the leaves, petals falling. Whale-oil soap, 10 lbs. nirotine-snlphate, 1} pts. Arsenate of lead, 8 lbs. Water, 200 gala. Lime-sulphur, 5 gals, nicotine-sulphate, li pts. Arsenate of lead, 8 bs. Water, 200 gals. •The alternative use of 5 or 6 gallons m this '-stance is determined by the season as well u by the variety of the apple. The measures indicated the table are United States, which are related to Imperial in the proportion of 5 to 4. It must be realized that the suggested dates for the first and second sprayings are merely approximate. They are considered suitable for such seasons as the springs of 1916 and 1917 proved to be, and it will probably be found necessary to vary the times of treatment in after years to suit conditions. The schedule here presented has been drafted to indicate the procedure under two sets of conditions, viz., a heav; and a light infestation of thripe. In cases of a light infestation in an orchard where no material damage has been caused, and in order to circumvent the possibility of the numbers increasing in later years, a single spray of whale-oil soap mixture or miscible oil mixture is considered all that is required for control purposes. The later sprays of lime-sulphur and arsenate of lead are intended to combat apple scab mainly, and other orchard pests. In a heavy infestation it is essential that the orchardist be prepared to expend a great deal of energy in undertaking combative measures. The lime- sulphur sprays for scab must be included as fourth and fifth sprays. It is considered possible that, if an orchardist endeavours under such con- ditions of infestation as have been experienced in the Saanich peninsula to combat the thrips thoroughly, he will, possibly in one year, perhaps m two, be able to adopt the .spraying schedule recommended for a light infestation. Preparation of Spraying Mixtvres. In order to dissolve the whale-oil soap warm water is desirable. Con- sequently, it is advisable to construct a rough, open fire-place at some convenient point in the orchard where water is readily available. When the soap has gone entirely into solution, it is emptieich °s fied is then added to the tank of thi !^^ • ° ^°}°^^- ^^« o" thus emulsi- with water. Th7 agitator is t hi tf spraymg machine which has been filed the tank thoroughl%S^ NlotineZthi?*° P'»V°*^ t»»e whole conten? of arsenate of leadfthe lattS as in the case of^j! T^ ^''^l ^ 'V^ded, followed by water It is well to T.mlZ:ri^:ti^;L^'iS^'^i^^^ ^^"^ ^"."^^'^ ^'^ of lead carries with it a certain peSSe of w.?Ln°""*"''^. ''"«n»t^ any chance the lead arsenate becomes Hrv*^l. n **®'^- Consequently, if by made in calculating tKnount r^uTred ^' "' ^'°''''"''' '"' '^^ '*"* ^"«t »^ a«d iWar^^ful'lc^Xt;^^^^^^^^^ '\ «-ons of 1916 that the cost of the ingmlSt! nSs^v for ™i?^ sPfaymg.* It was shown soap-nicotine-arsenate mixture br^Z^mShSL"*^ ^^T- »PP"«a«ons of the from 13 cents to as much ^ 40 cTnte oer t^ T^^ ^'*"?t" ^'^«™°* ""'^"'Is due to diflferences in the si^e of the trS t^hp 3^?i' •''''"''*'"!! '^^ ^^'o^" to be per acre, to differences in the cost of iSu^ to t hff"* °!!?J?^'" °'. *''««" P'«°ted of water, and to the degr^ of thoronJhni -^ accessibility or inaccessibilitv further shown that the eSTor labo^Sr £e^ '" rnP'^''^ *^^ ^P^^' '* ««« each imnute, whether the power mSneswerT^nT»** *° """^ ^ two cents for mg. Thus, it is import^t thTorrarXts sho^W T? T *''*."*"y «P™>- necessary in refilling the tanks or in a„ vZ- °.°* ^^^^V 'onger than incidental to sprayin| '"^ '" accomplishing the various operations Types of Machines and Nozzles. may be briefly stated that by farihe most^^H^' °/ ^''"P' ? »° "''^hard, it employment of high-power, motor-driven m.tfif5**'*°',?; '^"x"'*" '^'^''^^ the 175 to 200 pounds pressure If hS-%we?ma?h'?S^ generating from pressure than this are used, the mo^t eEvp^!-,?!.*' <^evelopmg a lesser expected; and more than one aDoSion mU k "'*^ *'"^°* ^ reasonably comparable to those received wher^ onll ^- ^^ ^fcessary to obtain result's Wgher pressure, inasmS I^ the ^wer ^achS" *™''*.?'u""* '" '"'"^e under shorter time and does it more efficiSy accomplishes more work in a coarse, driiTglpray'^'fitSrafc^^^ "^I ^^ '« ^^ **"»* throws a which throwa mCre spreaLg forS^Sf BDrr- *.f*° '°"°^ *•*** °°"'*'^ especially in the case Sf thosf .IS ^VeZ ^^ i5tVb"iroUS;S: ACKNOWLEDGMENTS. co-opTrltIJn\?lif V.^'l.T^^^ gratefully the cordial Agr culture, and of his office™ MessreR^Mw**',' '^••o^n«al Department of White assisted us in the cSvimr on of th^" ^"^°^ and E. W. White. Mr. T A. Brydon, G. Stewit!"7d fa^er B?o«'^w1,^'\*- T""°°«- ^o Messr... heir orchards for experiments spra^ng our Ct ?hi!fkr *'!l"*^ (?""?*'«« "' late summer and autumn of 1917 Mr w n^!^ *"''* ""'^ .**"«• '^"'OK tiu- the study of the soil phases of the work in Vh„?K^** ^'li employed to continue other investigations ° *'** absence of both authors engaged on •S«' ■ The Agri^ltural Gwett. of Canad,." Vol. 4. No. I, J„., 19,- PP. 13-1«. i.. .li-A.'. '^ *^-^ ;. No. 1, pp. 34-44, 1914. Karny, H. Revision der von Serville aufgesteilten Thysanoptera genera. Z(K)!ogi.sche Annalen, Bd. 4, Heft, 4, 1912. Moulton, D. The pear thrips and its control. U.S. Dei)t. Agr., Bull. 80, Part 4. Washington. 1909. Foster, S. W. and Jones, P. R. How to control the pear thrips. U.S. Dept. Agr., Cire. No. 131, Washington, 1911. Felt, E. P. 29th Report of the State Entomologist. N.Y. State Museum, Bull. 175, pp. 4.7-47, Albany, N.V., 1915. * )^ . H •i Ilii