Damage by the Douglas-fir cone moth, Barbara colfaxiana (Kearfott), in year N was significantly related to the size of the cone crop the preceding vear (N-1) in the interior of British Columbia but not at the coast. Damage by the Douglas-fir cone gall midge, Contarinia oregonensis Foote, at the coast was also significantly related to cone crop size the preceding year. Fluctuations in cone crop size appear to limit populations of these cone insects

Hedlin, A. F.

Miller, G. E.

Ruth, D. S.

Damage by the Douglas-fir cone moth, &lt;i&gt;Barbara colfaxiana&lt;/i&gt; (Kearfott), in year N was significantly related to the size of the cone crop the preceding vear (N-1) in the interior of British Columbia but not at the coast. Damage by the Douglas-fir cone gall midge, &lt;i&gt;Contarinia oregonensis&lt;/i&gt; Foote, at the coast was also significantly related to cone crop size the preceding year. Fluctuations in cone crop size appear to limit populations of these cone insects

Journal of the Entomological Society of British Columbia

46 J, E~To\tOL Soc , BHIT, COI ,l ' stBI A II I ( 1084 ). D Ec, 3 1. 10114 DAMAGE BY TWO DOUGLAS-FIR CONE AND SEED INSECTS: CORRELATION WITH CONE CROP SIZE C. E. MILLEH, A. F. HEDLIN A;"\iD D . S. RUTH Canadian Forestry Sen'ice. Pacific Forest Rcsea rch Centre. 50R W , Burnside TIoad. Victoria . B, C " V8Z IM5 ABSTRACT Dam age b,' thc Douglas- fir conc moth , Barbara ('o/jaxialla (Kearfott ), in , 'ca r N was significantl y related to the si ze of the cone crop the preceding yca r (N-I ) in the interior of British Columbia but not at the coast. Damage I)\' tbe Douglas- fir cone ga ll midge. COlltarillia oregoll(' lIsis Foote, at the coast was also significant'" relat ed to cone crop size the preceding !'ear, Fluctuations in cone crop size appt'a r to limit populations of these cone insects, RESUME L'ampleur des dommagcs causes par Ie perce-cone du Douglas (Barbara ('a /-, j axialla l Kearfott] ) a u cours de l"annce Nest ctroite ment liee it l"importanee de la rccoltc de cones de l"annee precedcnte (N - I) en Colombic-Brittani4uc. exception faite de la region co tiere, II cn va de meme pour les dommages causes par la cecidom yie des concs du Douglas (Co lltarinia oregonellsis Foote) sur la cote , II SCrll-ble Y avoir un rapport entre l"importance de la rccolte de cones et les populations de ces insectes , INTRODUCTION Douglas-fir cone moth, Barbara ("oljaxiallo (Kearfo tt ) (Lepidoptera: Oleth rcutidae) . and Douglas-fir cone gall midge. C(Jlltar i,jia oregollclIsis Foote (Diptera: CecidomYiidae), are the two most frc4uent and damaging seed pes ts of Douglas- fir. i'selu/otsll{!.a IlI c l1::i(,.I'ii ('.1irb ,) Franco. in Britisb Columbia, Douglas- fir cone moth occurs most com-mon'" in dn' interior areas whereas Douglas-fi r gall midg~ is m,;st common in wet coastal ar('a,s (II t·dlin et 0/, 1980 ), Both insect species are uni\'Oltine although in-di,'iduals may diapause for more than one winter (prolonged diapause) (Hedlin IU60. 1961 ), Adults of each species emerge and O\'iposit whcn seed cones are open to rcceive pollen, in April and earh' Mav, Feeding h,' co ne moth laryae begins in Ma,' and is completed b,' mid Jul~ ' at which time pupation takes place. The cone moth o" er\\'inters as a pharate adult (Sahota I' t 0/, 1982) in the cones , Lan'a l feedin g b,' cone ga ll midge, which ca uses ga ll for-mation on cone scales, occurs from '.1 a" to September. \Vhen the matured and dried cones arc wetted b,' rain in September the ful" '-developed lan'ae leave them to O\'erwinter in the duff, Dam age b,' co ne moth is the result of direct con-sumption of seeds (lledlin 19(0) while ga ll forma-tion b,' cone ga ll midge inhibits m 'ule de, 'elopment and impairs seed extractability (Johnson and Heik-kenen 1958), Cone a nd seed production b,' Douglas-fir va ries wideh ' O\'er a period of , 'ears, For exam ple . in the Vancouver Forest Region between 1935 and 1974. threc heavy crops. five medium crops, 10 lights crops, nine very light crops. and l 2 crop failures oc-curred (Dobbs £'t 0/, 1976), Variations in cone and seed a bundance affect both populations of a nd damage bv cone and seed insects attacking pines, PillllS 'pp .. and :\orwav spruce. Picco abies (L. ) Karst. (Mattson 197 1, 1980: Forcella 1978, 1080; Annila 198 1), but relationships bet\\'een cone crop size and damage bv Douglas-fir cone moth and cone gall midge have not been reported, The object ive of this study was to determine whet her or not damage bv these insect species was rela ted to cone abundance, MATERIALS AND METHODS Cones we re collected in August or September in the interior near Kcremeos. H,C .. between 19.59 and 1982 and at the coast near Lake Cowichan . l3, C .. between 1957 and 1982, No cone collections werc made in I U71 and 1972 at th e coa,st or in 1972 and 1076 in the interior. The number of cones col-lected each Yea r depended on the size of the cone crop and raogcd from 20 to 1080 , The number of sample trees ranged from 3 to 40, The cones were sliced longitudinall , ' along their axes (Winjum and Johnson 1960) and the numbers of fill ed and damaged seed.s per axia l sl ice were determined, Cone crops were rated at the time of collection as nil. Yer" light , light. moderate or heavy: tbe criteria for each rating were similar to those of Dobbs ct 0/, ( I m6), The num bers of damaged set'(:h per axial slice were grouped according to crop rating in the year of cone collectio n (:\ ) and in the previous ,'ear (N- I ). then submitted to analvsis of variance and Duncan's New Multiple Range Test. Damage counts were also grouped b,' , 'ears since preYious heavv or moderate crops and analyzed, Damage counts were transformed b,' log (x + I ) prior to anal ysis to cor-rect for heterogeneity of , 'ariance (Sakal and Rohlf 1969), Damage bv conc ga ll midge near Keremeos was not ana l!'zed because of thc low incidence of damage, J. E:--:To\ IOI. . SOc. RIl IT. COLDtn l A 8 I ( 198-1 ) . DEC. :31. I !J8-1 14 B colfaxlOfJo (INTERIOR I 12 CONE 10 CROP RATING 8 HE AVY 6 ME DIUM 4 2 1/ I I LIGHT , , VE RY LlGf NIL 195760 65 70 75 80 B. colfoxiona (COAST) 12 UJ CONE u :J 10 CROP <f) -' RATING <t X 8 HEAVY <t , " <f) " 0 " " UJ 6 I " , 11 • MED IUM UJ II II II " " " <f) " I. " /I0 4 II I UJ I I I <.:> <t ::; LIGHT '" , 0 I VERY LlGt NIL 19 57 60 65 80 C oreqonensis CO NE 10 CROP (COAST) RAT ING 8 HEAVY II " 6 II Ii MEDIU M I " I 4 I . I I,' .1 ., 2 . , " " \I LIGHT ". , \ - , ! VEW' LlGI II \ I NIL 1957 60 65 70 75 80 Fig. 1. Cone crop rating (dashed li ne) and damage (solid li ne) by B. colfaxialla a nd C. orego ll ellsis nca r i-.: crcmeos (in ter io r) and Lake Cowichan (coast ) from 1958 to 1982. RESU LTS AND DISCUSSION Damage by Douglas-fir cone moth and D ouglas-fir cone gall m idge flu ctuated widely from , 'ea r to year at both locations (F ig. 1) . Ave rage number ( ± S.E. ) of damaged seeds pe r ax ia l sli ce associa ted w ith heavy, medium . light and ''C['' light cone crops we re 3 . .59 ( ± 2.57), 3.S6 (± 2. 17) . .5. 7.5 ( ± O.SO) . and 7.90 ( ± 1. 02) respectively fo r Do uglas-fir co ne m oth near Kerem eos; 0. 13 (± 0.06). 2.00 (± 16S). 1.21 (± 0 .84 ) . and 2.0S ( ± 1.23) respective'" fo r cone moth near La ke Cowichan ; and 0 .21 ( ±0.0.5) . 4.S9 ( ±0.4S), 2.-19 (± 1.04 ). and 2.04 (± 1.1 7) respecti ve'" fo r Douglas- fi r cone gall midge near Lake Cowiehan. Diffc rences in damage among categories of cone crop size in the year damage occurred (:\) ,,:ere not significant (P = 0. 12) in eithe r species. Contrary to o ur results w ith cone moth and cone gall midge, an inverse relationship between seed abundance a nd dam age b,' the Douglas-fir seed cha lc ido id , M egas li g lllll s sp er lllo lrOp hl1s sp enn o lro p !zll s Wachtl (H "menoptera: Torymidae) , has been re ported in Br it ain (Hussey 19.56) . Damage by D o uglas-fir co ne moth ncar Ke rem eos and Duglas- fir cone gall m id ge nea r Lake Cowichan inc reased sign ificantly (P < 0.0 1) w ith 48 J. E :-: TO ,\lOI. . SOC . BB IT . C()j . l' ~ I B I A 8 \ ( \984 ). DI-:{ :. 3 1. 1984 z a:: <l w >-Z w if) +/ Z <l w ~ w u -' if) -' <I x <l "-if) o w w if) o w <.:> <l ~ <l o 14 /2 10 8 6 4 2 4 2 10 8 6 4 2 a ~ ab n = 2 3 t a ~ a c:b n = 2 5 a n = 2 5 B co/fox/ana ( INTERIOR) be i1- c + 5 10 B co/fax/ona (COAST) a a ~ m a rh 4 5 8 2 C. oregonens/s (COAST) b 7 2 HEAVY MED. LIGHT VERY NIL LIGHT CONE CROP RATING IN YEAR N-I Fig. 2. Number of seeds damaged by B. m/faxilJlj(J and C. urq!,ollclisis in relation to the size of the cone crop of the preceeding \·ea r . Bars under the sam e letter are not significanth' (P < 0 .05) different . Duncan's multiple range test . the size of the crop the pre\'ious \'ear (N- I) but nea r Lake Cowichan no relationship between cone moth damage and cone abundance the previous ~ 'ea r could be detected (P = 0. 85) (Fig. 2). Dam age b\ cone moth near Lake Cowichan was generalh' li ght but heaV\' dam age occurred periodicalh' (e. g., an a\'erage of 11 .5 damaged seeds per axial slice in 1973). Reasons for the periodic occurrenccs of heav\' damage are not known. In all instances in this stud\' . abundant crops (heavv or moderate ratings) were followed the next vear b\· light crops or crop fa ilures . Abundant cone crops allowed the insect populations to increase and the light crops which followed were usuall\ ' hea \'ih' damaged due to the high ratio of insects to cones . Damage by both Douglas-fir cone moth near Keremeos and Douglas-fir cone gall midge near Lake Cowichan was significantl\, (P<O.OI ) higher in the year following abundant crops than in other years (Fig. 3). Others ha\'e also noted this effect (Hedlin 1964 : 'vIattson 19S0: Annila 198 1). Dif-ferences in insect-caused damage among other years were not significant , although there was a tendenc\' for dam age to decrease as the period since the last abundant-crop increased. These results suggest that fluctu a ting cone abundance limits Douglas- fir cone moth in interior areas a nd Douglas-fir cone gall midge in coasta l areas. Sim il ar stud ies on red pine. J, E"TO\IOL. Soc:. Bnrr. CU I.u" I1 IA 81 (1 DS4 ), D EC. 31, HJIl4 4!) 12 10 w 8 (/) +1 z 6 <I w ::< 4 w u 2 --' (/) --' ~ x <I .... (/) 0 w 8 w (/) 0 w 6 l? <I ::< 4 <I 0 2 a b n = 6 4 a b n = 5 4 HEAVY lsI OR MED, 8. colfox/ono ( INTERIOR ) ab b 4 8 C oreqonens/s ( COAST) 4 7 2 nd 3 rd AND MORE NO, OF YEARS SINCE A HEAVY OR MEDIUM CONE CROP Fig, 3, :-.lumber of seeds damaged b, ' B, coljaxialla and C, oregoll e llsis in relation to the num ber of ",:ars since the last occu rrence of a hean' o r medium crop , Bars under the same letter are nut s i gn ifi c~nt'" (P <0, 05) different, Dunca n's multiple range rest, Pinus resino.'HI Aiton . and pinyon pines. {lillll."· pdulis Engelm , and p, mOllophylla Torr , & Frem" also showed that insect-caused cone damage " 'as limited IJ\ ' cone abundance the preceding , 'ca r (Les ter 1967: Mattson 197 1: Forcella 1878, 1980), Emergence of insects from prolonged diapause ca n result in hem'ier damage than expected in some , 'ea rs (Hedlin 1964: Annila 198 1), Induction of pro-longed diapause is im'erse'" correlated "ith cone abundance the , 'ea r following feeding Iw DOll glas-fir cone moth larvae at Keremeos (Hedlin c f ai, 1982), :\0 correlation between prolonged diapause and crop size was apparent for Douglas- fir cone ga ll mid ge at Lake Cowichan (H edlin 1964 ) , Emergence from prolonged diapause in re lat ion to sizes of subseq uent crops has not been exam ined in Douglas-fir cone moth or Douglas- fir cone gall midge but such em ergence appears to be related to crop size in Douglas- fir seed ehalcidoid (Annila 1982) and some insects attacking Nor"a,' sp ruce (Annila 19S 1) , Janzen (lD71 ) 1l\"\1othesized that errat ic seed pro-duction in plants has e, 'o lved in response to seed predation bv animals, Such ma\' be the case in Douglas-fir. T"picall\ ', modera te and hean' cone crops arc preceded b, ' c rop fa ilures or light crops, Sharp increases in cone produ ction can outstrip the reprod ucti\'e capabiliti es of th e insect popula t ions and a llow for production of large quantities of seed , There are few er crop failures and more cones arc usual", produced in , 'ea rs of light production at Kcremeos than at Lake Cm\"ichan which ma,' ac-count for the consistnth' hea\' ier damage oecu'rring at the form er location, Damage to pine co nes tends to be greatest where co ne production is most cons is-tent ('v1at tso n Unl ; Forcell a (980) , Consistent cone product ion frolll "ear to \'ear co uld result in loss of mos t seed even ' "ear due to build up of co ne and seed insect populations, ACKNOWLEDGEMENTS \Ve thank the Forest Insect and Disease Surve, ' Pacific Forest Research C entre , for ~,aking soni~ of the cone collections , 50 J. E :-':TO.\ fOI. . Soc. BlnT C()(X~ f BI.·\ HI ( HJ84) . D EC . 3 1. iD84 REFERENCES Annila. E . 198 1. Kausen kap, '- ja siementuhola isten kannam·a iht ci li . Commlln . I :lSt. For . Fenn . 10 1. 32 pp. Annila , E . 1982. Diapallse and population flu ctuations in Megastigmus specularis Wa lk,\· and Megasligmus spermotrophus Wachtl (lI \'lnenoptera. To rnnidae). Ann . Ent . Fcnn . -11\:33-36. Dobbs. R. c., D . G. W. Edwa rds. J. Konishi and D . Wallinger. Inl6. G uideline to collecting cones of B.C . conifers. B.C. Fo r. Sen ·.ICan. For. Sen ' . Joint n ep. No. 3, Victoria. B.C .. 9H pp . Forcella , F. 1978. Irregularit\· of pill\'on cone production a nd its relation to pin l'()Il cone moth predation . Madrono 25:170- 172. Forcella , F. 1980. Con e predation of pin\'on m ne beetle (Conop thorus edu lis) production . Am. I'\at . 116:594-598. Hedlin . A. F . 1960. On the li fe histon' of the Douglas- fir cone moth . Barbara colfaxiana (Kft .) (Lepidoptera: Olethreutidae), and O l1 e of its parasitcs. G lvp ta evetriac C ush . (H\'lnC11optera: Ichneulllonidae). C an . Ent. 92: 826-834. Hedlin , A. F. 1961. The life histon ' and habits of a Illidge . Con tarinia oregonensis Foote (Diptera: Cecidomyiidae) in Douglas- fir cones . Ca n. Enl. 93:9.'52-!J67. Hedlin . A. F . 1964 . n esults of a six-veal' plot studs' on Douglas-fir cone insect popu la tio n flu ctuations. For. Sci. 10 : 124-128. Hedlin , A. F .. II . O . Yates Ill. D . Cibrian , 13 . II . Ebel , T . W . Kocrber a nd E. P. \1e rkel. 1980. Co ne and seed insects of :\orth Ame rican co nifers. Ca n. For . Sen ·.I U.S. D .A. Fo r Sen ·./Secrct. Agric. Recur . Hid raul. , Mex ico . Victoria . BC .. 122 pp. Hedlin , A. F .. G. E . Miller and D. S. Ruth . 1!J82 . Induction of prolonged diapal.l se in Barhara eolfaxiana (Lep idoptera: O lethreutidae) : correlations with cone crops and weath er. Can. Ent . )j4:465-4 71. Husse\ ', N. W . 1956. The extcnd of seed-loss in Douglas-fir causeelll\' Megastigmus . Scot . For. 10: 101 - 107 . Jansen, D . H. 1971. Seed predation b,' anim a ls. Ann . Re\,. Ecol. S,·stemat. 2: 46.5-492. Johnson. l\. E .. anel II. J . lI eikkenen. 1951\. Damagc to seed of Douglas- fir b, ' the Douglas-fir cont' miJge. For. Sci. 4:274-282. Lester , D . T . 1967. Va ri ation in cone production of red pine in relation to \\·cather. Can . J. Bot. 45: 1683- 169 1. Mattson , \Y. J ., Jr. 1971. Helatio nship between cone crop size a nd cone dam age by insec ts in red p ine seed production-areas. Ca n. E nt . 103:6 17-62 1. Mattson , \.\, . J., J r. 1980. Cone resources a nd the ceology of the red pi ne cone bectle. Conopthorus resinosac (Coleoptera : Scol,·tidae). Ann . Enl. Soc. Am. 73:380-.3D6. Sahota . T. S. , D. S. Ruth. A. Ibaraki. S. H . Fa rri s and F. G . Pect . HJH 2. Di apa use in the ph aratc aelult stage of insect development. Can . E nt. 11 4 : 117!J - II I\3 . Sokal, R. R .. and F . J. Roh lf. 196!) . Biometry. W. H. Freema n & Co .. San franc isco. 776 p. Winjulll , J. K. , and N. E. Johnson . 1 !)60 . A modified -knife cone c utter for DOll glas- fir seed studies. J . For. 58:487-488 . 

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Damage by two Douglas-fir cone & seed insects: Correlation with cone crop size

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Damage by two Douglas-fir cone & seed insects: Correlation with cone crop size

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Journal of the Entomological Society of British Columbia