BI1IT. COI.UMB I A 74 11977). DE C'. 31, 1977 10 J. ENTOMOL. SOC

DISTRIBUTION OF LARICELLA (: ) AND ITS MAJOR PARASITES IN THE CROWNS OF WESTERN IN BRITISH COLUMBIA 1 ' B y GORDON E. MILLEI\' AND THELMA F INLAYSON

ABSTRACT sites Die/a­ The distribution of loleophora laricel/a Illbn.) and its para 1976)) doeerlls spp. ID nearcliells Yosh. and D. paci(icll S Yosh. IYoshimoto larch were and Spi/ochalc£s albi(rons (Walsh) in the crowns of western than 7.6 m determined for fi ve classes of trees. In open-grown trees more m above high, C. laricel/a densities were greater at 1. 5-3. 1 m than at 6. 1-7.6 ide, and on the the ground, on t he sunny side of a t ree than on the shaded s trees 3.0-4 .6 m outer half than on the inner half of a branch. In open-grown halves had high and in trees forming a closed canopy, only the outer branch in parasitism significant ly greater densities. The only s ignificant variation non­ by Dicladoeerus spp. occurred between branch halves in open-grown, on the inner roadside trees more than 7.6 m high, with more pa rasitism greater halves than the outer. Parasitism by S. albi(rons was significantly closed-canopy, at t he lower crown level than at the higher in open-grown, outer branch non-roadside trees that were more than 7.6 m high, and on the half than on the inner half in the same category of tree. s tribution of INTH()[)CCTION Webb 11953) exa mined the di on American larch, Little is known about the within-tree C. larieel/a K. Koch, but only on large, open­ distribution of the larch casebearer, Coleophora (Du Roi) grown trees. There have been no published laricel/a (Hbr~.) (Lepidoptera: Co leophoridae ), within-tree distribution of C. laricella an introduced pest, and its major parasites in reports of larch, Larix oceie/en/atis NutL British Columbia, in trees growing in different in western s of Dicladocerus spp. and S. albi­ situations. It is thus difficult to develop Distribution on we stern larch have been reported by adequate s ampling procedures. Die/adocl'ru s (rons et 01. (19721. but again only o n large, spp. In. ncarclicus Yosh. and D. paci(iclls Tunnock open-grown trees. Yosh. (Yoshimoto 1976) (Hymenoptera : E ul o­ e objective of this study was to determine phidae) andSpiloclralcis albi(rolls I Walsh) Th ee distributions of r. laricelia, (Hymenoptera: Chalcididae) were by far the the within-tr spp. and S. albi(rol/s in western most abundant species in a two-year survey of Dielodo('Pru" ch trees growing in various situat ions, to parasites of C. laricella (Miller and Finlayson lar e daLa that could improve sampling 1974 ,1977). provid techniques. METIIODS Crowns of 40 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: trees Description N um ber of Class ]0 ] Open-grown trees at least 91.4 m 1100 yd.) from road and over 12.2 m (40 ft.) hi gh 10 2 Same as Class except 7.6-10.7 m (25-35 ft .) high 3 Same as Class e xcept 3.1-4.6 m (10-15 ft.) hi g h 4 Same as Class except trees were roadside ]0 5 San,e as Class 1 except trees formed closed canopy. Trees sampled were at least twice hei ght of trees from the edge of stand

part ial ·'( ;r Uni\ 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

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. Bri t ish Columhia. IX = mean. SO = standa rd devialion)

Crown C. lariCl'lla de nsil.v % P arasitism Class Level (no ./ 100 fascicles) Dieiadncl'rlls s pp. S. al bif rons I ft. ) X SO x SO x SO

:;- 10 19 .1 5. 7 65 2.6 9. 1 ·1.1 20-25 9.7 2.6 8.4 2.9 4.2 3.1

2 ,S·IO 19.4 4.:; 7. I 2.3 l O.3 -1.7 20-25 8.7 1.9 7.7 2. 1 5.8 3.8

3 5-10 13.2 2.8 9.7 1. 6 7.3 2.6 20-25 11.0 2.2 9. 4 5.0 3. 1 3.4

4 5-1 0 23. 1 3.2 5.0 1. 6 7.6 35 20-25 10 .1' 2.3 6.9 3.4 2.8 2.8

5 5-l 0 17.2 2.8 6.6 4 .3 1 1. 2 5.8 =-c--=-==---==- - -_.. 12 J . E"TO"IOI.. Soc. BIl IT . COI. UMB IA 74 11977). DI·:c. 31 , 1977

I

50j Shaded Shaded 40 ~

~30 l- I C5 w I 20

10

2 May IS. 1974 collection June 13. 197 4 coll ecllon

50 Shaded

40

I- 30 I C5 w I 20

10

3 4 5 June 13. 1974 collecllon Fig. I . Schematic representation of within-tree distribut ions of ('oll'ophora lari('clla in one class of tree on 15 May 1974 and fi ve cl asses of trees on 13 June 1974 at Shoreacres, British Co lumbia. IN umbers represent number of casebearers per lOa fascicles. the outer being t hose of t he outer branch half and the illlwr t hose of the inner branch half) J. E N TO~IOI.. Soc BH IT. COLU~II3IA 74 (1977), D EC' 3 1, 1977

50

40

Shad ed - 30 l- I 11 9 0 '; 6 W I 20

10

2 3

50

40

- 30 l- I o w I 20

10

4 5 Fig. 2. Schematic representation of within-tree distributions of Dirladocl'rus spp. in fi ve classes of trees on 1:3 June 1974 at Shoreacres, Brit ish Columbia. (Numbers represent percentage pa rasitis m. the outer bein g t hose of the out er branch half and the inner t hose of in ner branch half) 14 J . ENTOMOL. Soc. BRIT. COLUMIllA 74 (1977), D F:c . 31, 1977

50 Sunny Shaded

40

30 l­ I (.9 w I 20

10

2 3

50

40

30 l­ I (.9 w I 20

10

4 5 Fig. 3. Schematic representation of within-tree d istributions of Spilochalcis alhifrons in fi ve classes of t rees on 13 June 1974 at Shoreacres, British Columbia. (Numbers represent percentage parasitism, the outer being those of t he outer branch half and the inner those of the inner branch half) J. ENTOMOL. Soc. BRIT. COLUMB IA 74 (1977). DEc. 3 1. 1977 15

(Sloan and Coppel 1965: Webb 1953). of C. laricelia, Bousfield and Lood (197 1) took The distribution of Diclac/ocerll s spp. could their samples fr om the terminal 45.7 cm (I S") be affected by movements of C. laricella after of branches rather t han whole branches. In pa rasitization . The a mount of spring movement open-grown trees more t han 7.6 m (2 5 ft.l high. by casebearer larvae is influenced by casebearer s uch a sampling technique would overestim ate density, greater movements occurring at higher paras it ism by S. albi(runs a nd underest imate densities (Webb 1953). At the densities parasitism by ]Jicladocerus spp. observed in t his study , casebearer movement The differences in distribut ions of both was not great enough to cause a difference in C. larice/fa a nd its pa rasites between classes the distribution of t he host between the two must be considered when meas uring casebearer coll ections, t he apparen t period of parasitiza­ populations or parasit ism. especially if less tion (Miller and Finlayson 1977) in Cla ss I t han whole- branch samples a re taken. and when trees. H ost movement probably is not a factor sampling trees of differing types. in the distribution of S. albi(rol1s as this species apparently attacks the sessile pupae of the host (Bousfield and Lood 1971). ACKNOWLEDGMENTS The within-tree distribut ions of Diclado­ We thank Drs. A. L. Turnbull a nd J. A. cerllS spp. and S. albi(runs in Classes 1 and 2 McLean, Department of Biological Sciences. are simila r to t hose in 9.1-1 2.2 m (30-40 ft.) Simon Fraser University. for advice on the trees in t he western United States (Tunnock statistical a nalyses. We are grateful fo r e/ al. 1972). The distributions of Dicladaceru" financia l support for t his wo rk from National spp. a nd S. albi(rolls wit hin trees probably Research Council Grant No. A4657 and in 1973 reduces competition for casebearers between from Contract OSP3-0228 from the Pacific t hese species on open-grown trees (Tunnock Forest Research Centre, Canadia n Forestry et al. 1972) . Service, Depart men t of the Environment. When measuring the degree of parasit is m Victoria. B.C.

Rl'ferences Bousfi eld. W. E. and R. C. Lood. 1971. Impact of parasites on the larch casebearer in the Northern Reg ion 1970. U.S.D.A. For. Servo Rept. 71-4 , Northern Region. Missoula, Mont. Dixon. W. J. 1973. BMD Biomt'dical Co mputer Progra ms. Univ. of Calif. Press, Los Angeles. Miller. G. E. and T. Finlayson. 1974. Native parasites of the larch casebearer, Co lcophora larice lla ( Lepidoptera: Co leo phoridae), in the west Koo tenay area of British Columbia. J . en tomo!. Soc. Brit. Colomb. 71 : 14-2l. Miller , G. E. a nd T . Finlayson. 1977. Parasites of the larch casebearer, Coleophora laritcll a (Lepi­ doptera: Coleophoridae), in the West Kootenay area, British Columbia. J . entomo!. Soc. Brit. Colu mbo (in press ). S loan, N. F. a nd H . C. Coppe!. 1965. Oviposit ion patterns a nd egg predation of the larch case­ bearer. Colt'ophora la rin'lla Hbn. in Wi sconsin . Univ. of Wisconsin For. Res. Note. No. 124 . Tunnock, S., M. McGregor and W. E . Bousfield. 1972. Distribution of la rch casebearer parasites in the crowns of western la rch trees in the Northern Region. U.S. D.A . For. Servo Kept. 72 -4. Northern Region. Mi ssoula, Mont. Webb. F. E. 1953. An ecological study of the larch casebearer. Coleophora laricell a Hbn. (Lepidop­ tera: Co leophoridae). Ph.D. Thesis, Univ. of Michigan. Ann Arbor, Mich. Yoshimoto, C. M. 1976. Revision of the genus Uic1adot'l'rus (Eulophidae: Chalcidoidea ) of Ameri ca north of Mexico, with particular reference to species attacking la rch casebearer (Lepidop­ tera : Co leophoridae). Can. E nt. lOS: 1173- 1206.