DISTRIBUTION of COLEOPHORA LARICELLA (LEPIDOPTERA: COLEOPHORIDAE) and ITS MAJOR PARASITES in the CROWNS of WESTERN LARCH in BRITISH COLUMBIA 1 ' B Y GORDON E
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10 J. ENTOMOL. SOC BI1IT. COI.UMB I A 74 11977). DE C'. 31, 1977 DISTRIBUTION OF COLEOPHORA LARICELLA (LEPIDOPTERA: COLEOPHORIDAE) AND ITS MAJOR PARASITES IN THE CROWNS OF WESTERN LARCH IN BRITISH COLUMBIA 1 B y GORDON E. MILLEI\' AND THELMA F INLAYSON' ABSTRACT The distribution of loleophora laricel/a Illbn.) and its parasites Die/a doeerlls spp. ID nearcliells Yosh. and D. paci(icll S Yosh. IYoshimoto 1976)) and Spi/ochalc£s albi(rons (Walsh) in the crowns of western larch were determined for fi ve classes of trees. In open-grown trees more than 7.6 m high, C. laricel/a densities were greater at 1. 5-3. 1 m than at 6. 1-7.6 m above the g round, on t he sunny side of a t ree than on the shaded side, and on the outer half than on the inner half of a branch. In open-grown trees 3.0-4 .6 m high and in trees forming a closed canopy, only the outer branch halves had significant ly greater densities. The only significant variation in parasitism by Dicladoeerus spp. occurred between branch halves in open-grown, non roadside trees more than 7.6 m high, with more pa rasitism on the inner halves than the outer. Parasitism by S. albi(rons was significantly greater at t he lower crown level than at the higher in open-grown, closed-canopy, non-roadside trees that were more than 7.6 m high, and on the outer branch half than on the inner half in the same category of tree. INTH()[)CCTION Webb 11953) exa mined the dis tribution of Little is known about the within-tree C. larieel/a on American larch, Larix laricina distribution of the larch casebearer, Coleophora (Du Roi) K. Koch, but only on large, open laricel/a (Hbr~.) (Lepidoptera: Co leophoridae ), grown trees. There have been no published an introduced pest, and its major parasites in reports of within-tree distribution of C. laricella British Columbia, in trees growing in different in western larch, Larix oceie/en/atis NutL situations. It is thus difficult to develop Distributions of Dicladocerus s pp. and S. albi adequate sampling procedures. Die/adocl'ru s (rons on we stern larch have been reported by spp. In. ncarclicus Yosh. and D. paci(iclls Tunnock et 01. (19721. but again only on large, Yosh. (Yoshimoto 1976) (Hymenoptera : E ul o open-grown trees. phidae) andSpiloclralcis albi(rolls I Walsh) The objective of this study was to determine (Hymenoptera: Chalcididae) were by far the the within-tree distributions of r. laricelia, most abundant species in a two-year survey of Dielodo('Pru" spp. and S. albi(rol/s in western parasites of C. laricella (Miller and Finlayson larch trees growing in various situat ions, to 1974 ,1977). provide daLa that could improve sampling techniques. METIIODS Crowns of 40 western larch trees in fi ve classes were sampled on 13 June 1974 at Shore acres, British Columbia. The five classes of trees and the number in each class were: Class Description N um ber of trees ] Open-grown trees at least 91.4 m ]0 1100 yd.) from road and over 12.2 m (40 ft.) hi gh 2 Same as Class except 7.6-10.7 m 10 (25-35 ft .) high 3 Same as Class except 3.1-4.6 m (10-15 ft.) hi g h 4 Same as Class except trees were roadside 5 San,e as Class 1 except trees formed ]0 closed canopy. Trees sampled were at least twice hei ght of trees from the edge of stand lBased nn a Lh ('s i ~ su h m itted hy liw ~(' n i nr autho r in part ial ·'( ;r<l<iual l' s tudent and P ro l' e ~ sor. resprcti\'({\" Simon Fr a ~ f'r fu lfillmen t nf a n M .Sc. degrcf> Uni\'l'fs it .,", Burn;:")\", B.C. V~ ;\ I Sf) J . E ,\;TOMO I. Soc BH IT. CO I. U\IHI,\ 74 (19 77 ). DI'e 3 1. 1977 11 Samples from Class I t rees were a lso take n ) ). The dens it ies were s ignificant ly hig he r on 15 May 1974 bu t were analyzed for distri on t he outer hra nc h ha lves t han on t he in ner bution of C. laricel/a only. in a ll classes. S ig nificant ly hig her densit ies Samples were taken at two crown levels: occurred at t he lower crown level t ha n at the 1. 5-3. 1 m 15- 10 fl.) a nd 6.1-7. 6 m 120-25 fl. ) hi g he r in Classes I, 2 a nd 4 but no s ig nifi can t a bove t he g r ound . T wo primary bra nches were differ ences occurred between crown levels in take n from both t he s unny a nd shaded sides of C lass 5. Dens ities were a lso s ignificantly hig he r each t ree from each crown level a nd cu t in ha lf. o n t he s unny sides of t rees t ha n o n t he shaded The branch halves were mass-reared in pa irs s ides in Cla's ses I , 2 a nd 4 but no sig nificant according to tree, cr own level. s ide o f t ree. and d ifferences between sides of t rees occurred in bra nch ha lf. Reari ng was d one in 30.5x6 1. 0x Classes 3 a nd 5. The dis tribut ions did not d iffer 30.5 em II x2x I ft. ) cages construct ed fro m in Class 1 t rees between t he two collectio ns. corrugated pa per car tons, t he tops of which The o nly significant var ia tion in parasit ism wer e replaced wi t h 0.2 m m mesh. by Dicladocerus spp . occurred between bra nch Pa rasites were collected daily and placed halves, wit h mo re pa rasit is m on t he inner t ha n directly in to 70% etha nol. After parasite on the outer halves, in Classes I a nd 2 (Fig . 2 ). emer gence was co mpleted , host cases were No s ig nifican t variatio ns occurred between removed ma nua lly a nd t he number of fascicles crown levels or s id es of trees in a ny of t he cou nted . classes, or between bra nc h ha lves in Cla sses For s tatistical a na lyses, log 10 x t ra ns for 3, 4 a nd 5. mations were d o ne on C. laricel/a de nsit ies Pa rasit ism by S. albi(rol/s was s ig nificant lv (numbe r pe r LOO fascicles) a nd arcs ine t ra ns g rea ter at t he lower crown level t ha n a t t he forma tions were calcula ted for per centage hig he r in Classes j , 2 a nd 5: and on t he outer pa rasit is m data. In a na lyses of varia nce I Dixon bra nc h ha lves t ha n on t he inne r in Classes I 1973 ) o f t he in t ra-tree d istribut io ns of each a nd 2 IFig . 3 ). No sig nifica n t differences class, t rees were a ll owed to go random, result occurred between bra nch ha lves in Classes 3. ing in conservative F values. The data a re 4 a nd 5, or between cr own levels in Class 4. presen ted in t he un t ra ns formed form. DI SC LSS ION RES ULTS W ebb (1 953 ) found dist ribu t io ns of C' lo ri There were no sig nifican t differences cel/a simila r to those in the c rown levels and between t he t ree classes in mean density of branc h po rtion in open-g rown t ree classes I C. laricel/a or mean percen tage pa rasit ism by to 4 of t his study, i.e.. higher casebearer U iclac/oc('rtl8 spp. or by S. albi(roll8 in t he de ns ities a t t he bottom of t he crown than a t t he crown levels I T able 1). C. la ricel/a de nsit ies t op a nd on t he termina l pa r t of t he bra nc h t ha n var ied significantly between c rown levels, at t he base. The a bunda nce of C. laricel/a between s ides of t he tree, and between bra nc h la r vae a nd pupae on t he s unny s ide of the t ree halves in Classes I. 2 and 4: a nd between a nd t he outer ha lf of t he bra nc h may re fl ect t he branch ha lves only in Classes 3 and 5 (Fig ure oviposit ion site preferences of t he fe ma le moths TABLE I. Density of Cnl,'ophora laritt'lla a nd percen tage pa r asitism by Dicladocerw; s pp., and by Spiln('hakis alhifrnlls in fi ve classes o f t rees on 13 ,June 1974 a l S ho reacres.