ENTOMOLOGICAL SOCIETY OF BRITISH COLUMBIA, PROC. (1951), VOL. 48, AUG. 15, 1952 81

NOTES ON THE POPULATION AND PARASITISM OF THE , ERICHSONII (HTG.) (: ), IN BRITISH COLUMBIAl J. H. McLEO02 Diological Control Investigations Laboratory, Vancouver, B.C. In British Columbia the larch saw­ a thorough search of the infested area, fly, Pristiphora rrichsonii (Htg.), was only 2,500 cocoons were obtained. The first reported in 1930 in an area about numbers of cocoons colIected in the 30 miles north of Fernie. In 1933 a 3 years do not accurately represent survey showed that the infestation the change in population, but there covered a large area in and around was a reduction in 1950. All avail­ Fernie. Cocoon samples were obtain­ able data have been examined to de­ ed at that time and were examined at termine the factor or factors respon­ the Forest Laboratory, Vernon, sible for the reduction in host popula­ B.C., and at the Dominion Parasite tion and its effect on M. aulietls. Laboratory, Belleville, Ont. No evi­ In 1949 many of the larch trees in dence of "parasitism was found, and the infested area were affected with parasites were released in the infested needle cast, the symptoms of which area. The first colony of parasites, are a premature yellowing and early comprising 393 males and 280 females dropping of the needles. This caused of Mesoleills aulicus (Gra v.), was re­ some larval mortality during the feed­ leased in July, 1934, at Lizard Creek, ing period, but no significant reduc­ 2 miles from Fernie. tion in the number of cocoons coIlected P. erichsonii spread rapidly north and in the most heavilv infested area. It east following the distribution of is possible that the viability of the western larch, Larix occidentalis N'Jtt., larvae in the cocoons was reduced, which, in the main, is confined to the but no evidence was obtained to sup­ southern interior of British Columbia. port this theory. Emergence was As parasites became available they normal from the 130,000 cocoons col­ were released in the newer areas of lected in October and Novemher, 1949. infestation to hasten establishment and stored in an unheated lahoratory and distribution. Details concerning room over winter, Random sample"s parasite releases and host distribution of cocoons taken from the 1948, were given by Hopping, Leech, and 1949, and 1950 coIIections were dissect­ Morgan (1943). At no time has P. ed; the percentages of dead larvae ~richsollii reached outbreak proportions were 16.5, 7.5, and 12.0, respectively in British Columbia except in isolated (Table I). There was a decrease of areas. The population in each of the 9.0 per cent. in larval mortality of P. heavily infested areas for which there trichJonii in 1949 rather than an in­ are re~ords became heavily parasitized crease, which would have occurred if hv M. auliClJs and subsided without needle cast' had affected the viahility s~rious injury to the trees. ' of the larch sawfly larvae. In 1948 a project was initiated to The winter of 1949-50 was unusual­ provide colonies of M. auliCllJ from ly cold and a heavier-than-normal British Columbia for release in West­ s"nowfall occurred. Weather records ern Ontario, Manitoba, and Sa,skat­ taken at the Grand Forks office of the chewan.1 n that year 105,000 P. Canada Department of Transport (14 el'ichsonii cocoons, heavily parasitized miles from the infested area) show hv' M. aulietiS, were obtained. Tn 1949 that the avt;rage temperature was be­ o;le hundred and thirtv thousand co­ low normal during the winter of 1949- coons were collected. "In 1950, after 50. ,On May 19, 1i950,.although nruch of the infested area was stil1 covexeci 1 ~Gntnbutioll No. 2913, Division of Entomology, Scie.Tl~e Ser:vi!:e, Dep,artme,nt of .Agriculture, .pttqwa, . w:ith snow,a cnIIection ,of cocoons Canada. was,obt~n~d: it .was immediaJely L Agricultur~1 Research ' Officer. d-- --. -- < 82 ENroMOLOGICAL SOCIETY OF BRmm COLUMBIA, PROC. (1951), VOL. 48, AUG. 15, 1952

placed in rearing at unheated room The next factor that was consid­ temperature (average, 62°F.) in Van­ ered was parasitism. An increase in couver. The emergence from this col­ the percentage parasitism could have lection was normal; therefore, it must accounted for the decrease in the P. be assumed that the reduction in popu­ erichsonii population in 1950. However, lation of P. erichsonii was not caused there was a decrease in parasitism by winter mortality. amounting to 6.7 per cent. (Table I).

TABLE I

Larval mortality, and paraSitism, of Prisliphora erhhsonii (Htg.) In British Columbia, 1948, 1949, and 1950.

1949 I 1950 1___ .. _ ~948 __ _ --_._------,-- - - - ,------;--- - - I Number Per cent. Number Per cent Number Per cent.

Cocoons dissected 1464 100 536 100 441 100 P. erichsonii larvae dead (causes 248 16.5 40 7.5 53 12.0 unknown) living 1216 68.2 496 92_5 388 88.0 M. aulicuJ larvae living 829 83.5 305 61.5 213 54.9

=== = = -=---'----"'=---==-=--==,-,---,,-=== _-==_-==---::_ ~_=. _=c_.c'_-='_:- -. _ ~:~---'--~_------'-·c.c- -=-----".--=--=-:-=- c.. _'------"-- ~-_----

Evidently, the mortalities caused by The first concrete evidence that needle cast, winter weather, and para­ some P. erichsonii remained in diapause sitism were not responsible, individu­ throughout the summer of 1950 was ally or collectively, for the reduction found when the intact cocoons from in the population of P. erichsonii in a laboratory-reared collection were 1950. opened in August, 1950. There were Finally, the diapause factor was 1,181 cocoons in the collection and of considered. In British Columbia P. these 88, or 7.45 per cent., contained erichsonii normally completes its life­ living P. erichsonii larvae. This per­ cycle in 1 year, but in 1950 there was centage was not large enough to evidence that a portion of the popula­ account for the important decrease in tion remained in diapause. In Sep­ P. erichsonii population in 1950. Duing tember, 1950, the cocoons were most May and June, when normally dia­ numerous in the area most heavily pause is broken and pupation occurs, infested in 1949; previously, the the temperature in the laboratory was centre of infestation had changed considerably higher than in the field. The average temperature in the labor­ from year to year and had usually atory was about 62°F.; at Grand moved in a westerly direction. The Forks, which is about 1500 feet lower cocoons were darker in colour than in elevation than the area of P. freshly formed cocoons normally are, erichsonii infestation, the average tem­ and many of them were collected peratures during- May and June were under trees from which cocoons had 51°F. and 61 OF. respectively. The been taken in 1949. These trees show­ higher temperature in the laboratory ed fewer signs of larval feeding than could have been responsible for a would have been expected if the smaller portion of the P. erichsonii larvae that formed cocoons under larvae remaining in diapause in the them had fed on the 1950 foliage. laboratory than in the field. ENTOMOLOGICAL SOCIETY OF BRITISH COLUMBIA, !'ROC. (1951), VOL. 48, AUG. 15, 1952 83

TABLE II Average weights of P. erichsonii cocoons in 3 size groups, 1949 and 1950.

1949 1950

._---- Weight Size of cocoons decrease, mg. Number Average Number I Average weight, mg. jweight, mg. I ===== Large (lOi to less than 1Umm.) 145 86.2 113 83.5 2.7 Medium (91 to less than lO ~mm.) i 170 73.6 229 69.2 3.4 Small (8 to less than nmm.) 221 55.5 99 50.9 4.6 ------'------'-- - - -_._--

If a large portion of the P. erichsonii H owever, there was an important larvae did in fact remain in dia­ difference in the percentages of pause in the cocoons during the sum­ medium and small cocoons (Table III). mer of 1950, it would be expected that There was a large increase in the the cocoons collected in the autumn percentage of medium and a large of 1950 would be similar in weight decrease in the percentage of small and size to those that were collected cocoons in 1951). This seemed to be in the autumn of 1949. There was no important difference in the weights irrefutable evidence that the cocoons of cocoons in the two years (Table II). collected in 1950 could not have been Th~ slight decrease that occurred in part of the 1949 population as they 1950 could have been caused by desic­ must have been if the larvae in them cation during the summer of 1950. had remained in diapause.

TABLE III Percentages of large, medium, and small cocoons of P. erichsonii, 1949 and 1950.

1949 1950 Size of cocoons - - - _ . ._- - Number Per cent. Number Per cent

Large 145 27.1 113 25.6 Medium 170 31.7 229 51.9

Small 221 41.2 99 22.4

An explana1ion for this anomaly adults of P. erichsonii were incubated. was found when the rearing data were The numbers of each and the number examined. The random collection of M. aulicus that remained in dia­ from which the 88 larvae remaining in pause are shown in Fig. 1, each plot­ diapause were dissected was com­ ted point representing the number of pri sed of 1,181 cocoons, and from specimens for a 5-mg. group ; e.g., these 634 adults of M. aulicus and 309 from cocoons weighing 46 to 50 mg. 84 ENTOMOLOGICAL SOCIETY OF BRITISH COLUMBIA, PROC. (1951), VOL. 48, AUG. 15, 1952

4 adults of P. erichsonii emerged. It This corresponds closely with 73.6 . was seen that there was complete mg., the average weight of the med­ emergence from all cocoons that ium-sized cocoons in 1949 (Table II). weighed less than 60 mg. and that If this occurred in the field, it would the remained in diapause only explain the reduction in the number of in the larger and heavier cocoons. small cocoons and the increase in the The largest numbers that remained number of medium-sized cocoons In in diapause were in the 75-mg. group. 1950 (Table III).

160

140 f\ 120 I \ I \ I \ 100 I \ L- I \ V J \ ~80 I \ ::> / \ Z / \ :•...... •. 60 I \\ / .... "" / , ., 40 Ii'

I I • '. 0 20 / •• 0 ..... • '. ,P o· 0 /" :-..... _. -0.••••••• d •.••• 0· °2'L5~~3~3~-4~'~-4~9~~5~7~-6~5~~73~~8~1~~8~9-~~9~7~~IO5 Cocoon Weight in Mg.

Fig, I.-Numbers of adults of Pristiphora erhhsonii (Htg.) ( ....) and of Mesoleius au/ieus (Grav.) ( - - - -) that emerged, and numbers of larvae of M. aulieus remaining in diapause ( ), from various weights of cocoons of P. eriehsonii collected in British Columbia in 1949 and reared in 1950; each plotted point represents the number of specimens for a 5-mg. group, e.g, from cocoons weighing 46 to 50 mg. 4 adults of P. eriehsonii emerged.

All the information obtained from or parasites were responsible for the field observation and laboratory rear­ unusual population reduction. ing data supports the opinion that the Although parasites are not consid­ reduction in abundance of P. el'ichsonii ered to have been responsible for the in 1950 was caused by a large portion reduction in the population of P. erich, of the population remaining in dia­ sOliii in 1950, they are an important pause. There was no evidence that control factor. This opinion is sup­ needle cast, winter weather conditions, ported by the record of percentage ENTOMOLOGICAL SOCIETY OF BRITISH COLUMBIA, PROC. (1951), VOL. 48, AUG. 15, 1952 85 parasitism obtained by dissection that the parasite had synchronized its (Table I) and by the proportion of development with that of the host, M. aulims adults that emerged from the thus ensuring the continued effective­ random collection of 1,181 cocoons of ness of the parasite. P. erichsonii collected in 1949 and rear­ Referen~es ed in 1950 (Fig. 1). Further evidence Hopping, G. R, H . B. Leech, and C. V. G. of the effectiveness of M. aulicus was Morgan. 1943. The larch sawfly, Pristi­ obtained when the diapause P. erich­ phol'a erichsonii (Hartig), in British Colum­ sonii larvae were dissected in August, bia, with special reference to the cocoon parasites Mesoleills tenthredinis ~1 orley and 1950; 89.8 per cent. of them contained Tritl1eptis kiligii (Ratzeburg). Sci. Agr. 24: living M. aulims larvae. This showed 53-63.

BIOLOGY AND CONTROL OF THE CHERRY CASE BEARER, COLEOPHORA PRUNIELLA CLEMENS, IN BRITISH COLUMBIA! D. B. W ADDELL2 Fruit Insect Laboratory, Summerland, B.c. An outbreak of the cherrv case .. in 1912-13. Later Glendenning (1923) bearer, Coleo phora pruniella' Clem., noted its presence in that vaHey but occurred in two adjacent apple not as a serious pest. Hutson (1931, orchards at Creston in the Kootenay '32) reported the cherry casebearer to Valley in 1947. This is the first record be a spectacular pest of cherry in of this species for the Province of Michigan. Its depredations in or­ British Columbia. The insect was chards were first noted in 1929, al­ reported causing serious damage to though known on wild black cherry apple at Salem, Oregon, in 1937, by from the time of its description. Hsiao and Mote (1939), marking the most westerly record for this specie!;. LOCALITY, VARIETIES OF FRUIT ATTACKED, Known since 1861, when it was des­ AND SEVERITY OF INFESTATION cribed, the cherry casebea! er has been The coleophorid infestation was con­ a serious pest of both cherry and tined to two adjacent orchards one apple in the United States and Canada mile southeast of Creston, at the during the past 25 years. Petch and southern end of the Kootenay Valley. Armstrong (1926) recorded that apple One orchard contained only mature orchards in the Lake St. Louis area McIntosh apple trees, the other a of Quebec had been heavily infested mixed planting with McIntosh pre­ for several vears. These authors dominating but including Delicious, were the first to give adequate descrip­ Jonathan, Winter Banana, and scat­ tions of all stages of the insect and tered pears and cherries. All fruit an adequate account of the life­ varieties were attacked, McIntosh history. Petch and Maheux (1930) most severely; the heaviest infesta­ reported little damage to apple in tion and damage occurred in the or­ Quebec from this species, whereas 5 chard with the mixed planting. The per cent. injury w as caused by the difference in severity of damage be­ cigar casebearer, Coleo phora occidentis tween the two orchards was due to Zel!. The latter species, the only an application of dormant oil-dinitro casebearer hitherto recorded as having orthocresol to the McIntosh planting caused damage to orchards in British but not to the mixed planting. Columbia, was reported by Treherne The infestation was first noted in (1914, p. 25) to be present in every the fall of 1947, when the twigs and orchard of the Lower Fraser Valley fruit spurs were literally covered with 1 Contribution No. 2888, Division of Entomology, overwintering cases. Evidently some Science Service, Department of Agricu1ture, Ottawa, damage had occurred in 1947 but had Canada. ;) Associate Entomologist. not been reported by the growers. In