RJ WEST,^ M KENIS,' GW Bun, and SM BENNETT Abstract
Total Page:16
File Type:pdf, Size:1020Kb
PARASITOID COMPLEX OF ZEZZUPHERA CANADENSZS (LEPIDOPTERA: TORTRICIDAE) AND EVALUATION OF TYCHERUS OSCULATOR (HYMENOPTERA: ICHNEUMONIDAE) AS A BIOLOGICAL CONTROL AGENT RJ WEST,^ M KENIS,' GW Bun, and SM BENNETT Natural Resources Canada, P.O. Box 960, Comer Brook, Newfoundland, Canada A2H 653 Abstract The Canadian Entomologist 131: 465 - 474 (1999) A survey of larval and pupal populations of the spruce bud moth, Zeiraphera canadensis Mutuura and Freeman (Lepidoptera: Tortricidae), conducted from 1994 to 1996 in eastern Newfoundland, disclosed that the incidence of endemic parasit- ism by Hymenoptera was up to 50% for Tycherus osculator (Thiinberg) (Ichneu- monidae), up to 15% for Earinus zeirapherae (Walley), under 3% for Ascogaster (Wesmael 1835) sp. and Clinocentrus (Haliday 1833) sp. (Braconidae), and under 1% for Lamachus (Foerster 1868) sp. and Triclistus (Foerster 1868) sp. (Ichneu- monidae). Tycherus osculator, E. zeirapherae, Ascogaster sp., and Clinocentrus sp. represent new distributional range extensions to Newfoundland, and to the nearctic region in the case of Z osculator. The biology of European populations of Z osculator was studied on a natural host, Zeiraphera diniana (GuenCe). Only fe- males overwintered and ovarian maturation did not occur until after several months of exposure to near-freezing temperatures. Tycherus osculator successfully parasit- ized prepupae and pupae of Z. diniana of all ages but, in the laboratory, appeared to prefer pupae. Host feeding by Z osculator was common but not necessary for ovar- ian maturation. Tycherus osculator imported from Europe attacked and successfully developed within the spruce bud moth host in laboratory screenings. Morphological comparisons indicated that Z osculator reared from Z. canadensis were smaller than those reared from Z. diniana. Tycherus osculator obtained from either Newfound- land or Europe may have potential as a biological control of Z. canadensis in main- land Canada, where it is presently absent. West RJ, Kenis M, Butt GW, Bennett SM. 1999. Complexe parasitoide de Zeiraphera cana- densis (Lepidoptera: Tortricidae) et Bvaluation de Tycherus osculator (Hymenoptera: Ichneumonidae) titre de biopesticide. The Canadian Entomologist 131: 465-474. Une Ctude des populations larvaires et nymphales de la tordeuse de I'Cpinette, Zei- raphera canadensis Mutuura et Freeman (Lepidoptera: Tortricidae), effectuke de 1994 a 1996 B I'est de Terre-Neuve a montrC que le taux de parasitisme par les Hy- mCnoptbres atteignait 50% pour Tycherus osculator (Thiinberg) (Ichneumonidae), 15% pour Earinus zeirapherae (Walley), moins de 3% pour Ascogaster (Wesmael 1835) sp. et Clinocentrus (Haliday 1833) sp. (Braconidae), et moins de 1% pour La- machus (Foerster 1868) sp. et Triclistus (Foerster 1868) sp. (Ichneumonidae). Ty- cherus osculator, E. zeirapherae, Ascogaster sp. et Clinocentrus sp. sont pour la premibre fois mentionnCs Terre-Neuve alors que T. osculator n'avait encore jamais CtC trouvC dans la rCgion nCarctique. La biologie de populations europkennes de Z osculator a Ctt CtudiCe sur un h8te naturel, Zeiraphera diniana (GuenCe). Seules les femelles ont hivernC et la maturation ovarienne n'a CtC observCe qu'aprks une pCriode hivernale de plusieurs mois B basse tempkrature. Tycherus osculator a para- sit6 avec succbs les prC-nymphes et nymphes de tous Bges mais, au laboratoire, il a prCfCrC les nymphes. Les femelles ont souvent CtC observkes s'alimentant sur I'hhte, mais cette activitC n'Ctait pas nCcCssaire a la maturation ovarienne. Une population F'resent address: Box 515, Portugal Cove, Newfoundland, Canada, AOA 3K0 F'resent address: CABI-Bioscience, 1, chemin des Grillons, DelCmont CH-2800, Switzerland 465 466 TH@CANADIAN ENTOMOLOGIST JulyIAugust 1999 europtenne de T. osculator a parasit6 avec succbs la tordeuse de 1'Cpinette au labo- ratoire. Des comparaisons morphologiques ont montrt que les T. osculator euro- pCens obtenus de Z. canadensis Ctaient plus petits que ceux obtenus de Z. diniana. Tycherus osculator, de Terre-Neuve ou d'Europe, est consider6 cornme un agent de lutte biologique potentiel contre Z. canadensis sur le continent nord-amCricain, ou il est apparemment absent. Introduction The spruce bud moth, Zeiraphera canadensis Mutuura and Freeman (Lepidoptera: Tortricidae), is native to North America and attacks white spruce, Picea glauca (Moench) Voss (Pinaceae), throughout Canada and the northeastern United States (Turgeon 1992). Damage by spruce bud moth may cause severe crown deformation, multiple leaders, and reduction in height and volume growth (Carroll et al. 1993). The spruce bud moth is expected to become a pest in western and central New- foundland when spruce plantations are established in areas traditionally covered by bal- sam fir, Abies balsamea (L.) Miller (Pinaceae), forest, but little is known of parasitoid species attacking this insect in Newfoundland. An understanding of the endemic parasi- toid complex is necessary to identify vacant niches that could be exploited by exotic parasitoids imported as biocontrol agents and indicate occupied niches where intro- duced parasitoid species would be obliged to compete. White spruce trees growing on the Avalon Peninsula near St. John's are severely attacked by spruce bud moth and pro- vide excellent sources of material to determine endemic parasitoid levels. The native complex of natural enemies of the spruce bud moth in Canada was summarized by Turgeon (1992) from records made in Quebec and New Brunswick. Trichogramma rninutum Riley and Trichogramma sp. (Hymenoptera: Trichogrammatidae) have eclosed from spruce bud moth eggs at incidences over 50% (see also Ostaff and Quiring 1994; Ostaff 1995). Twenty-four species of Hymenoptera (nine Braconidae, three Pteromalidae, three Eulophidae, and nine Ichneumonidae) have been recorded as attacking larvae or pupae. Rates of apparent larval parasitism recorded in Quebec were under 13% (Pilon 1965). However, Earinus zeirapherae (Walley) (Ichneumonidae) ac- counted for over 50% parasitism of larvae in New Brunswick (Turgeon 1992). Mills (1993) and Schonberg (1993) reported the results of surveys of parasitism of European populations of Zeiraphera ratzeburgiana (Ratzeburg), Zeiraphera diniana (GuenCe), and Zeiraphera rufimitrana (Herrich-Schaffer), three species with a life his- tory similar to that of the spruce bud moth. Mills identified several Ichneumonidae, Phytodietus (Gravenhorst 1829) spp., Chorianaeus cristator (Gravenhorst), and Ty- cherus osculator (Thiinberg) as potential candidates for the control of spruce bud moth. Schonberg (1993) recommended that the Ichneumonidae 7: osculator and Tranosema carbonellurn (Thomson) be studied further as potential candidates for introduction on the basis of their specificity to Zeiraphera species from Europe and compatibility with the life cycle of the spruce bud moth. We present a summary of larval and pupal parasitism of the spruce bud moth pop- ulations from eastern Newfoundland and results of screening 7: osculator reared from Z. diniana against larvae and prepupae of spruce bud moth in the laboratory. Additional data from laboratory studies are presented on the behaviour and development of T osculator exposed to Z. diniana. We studied 7: osculator because it is the most im- portant natural enemy of Z. ratzeburgiana (Schonberg 1993), the European species of Zeiraphera most similar to 2. canadensis. We worked with Z. diniana because Z. ratzeburgiana populations were too low to allow collection of sufficient numbers of pupae during the period of study. Volume 131 THE CANADIAN ENTOMOLOGIST 467 Methods Local Parasitoid Complex. Study sites and plot layout. The study was conducted during the summers of 1994-1996 near St. John's, Newfoundland, Canada. Field sites containing open-grown, white spruce trees infested by Z. canadensis were surveyed to determine its endemic parasitoid complex and to assess levels of parasitism. The first site (Arterial, 47"3ON, 52"47W), located 1 km west of St. John's, was 3 ha in size, dominated by 2-3 m tall white spruce and containing a mixture of balsam fir; white birch, Betula papyrifera Marshall (Betulaceae); and pin cherry, Prunus pensylvanica L. (Rosaceae). The second site (Torbay, 47"39'N, 52"43W), located next to the ocean and 6 km north of St. John's, was a 1- to 2-ha stand of 2- to 5-m high white spruce. Ten trees, about 2 m tall and showing evidence of moderate to severe defoliation by the spruce bud moth, were sampled at each location each year. Larvae. Branches were sampled once a week starting at the time of spruce bud moth egg hatch, usually at the end of May. On each sampling date, two midcrown branch tips, about 25 cm in length, were arbitrarily chosen and pruned from each tree, placed in labeled paper bags, transported in coolers, stored at 5°C upon arrival at the laboratory, and processed within 24 h. Newly burst buds and elongating shoots were dissected to obtain spruce bud moth larvae. Seventy-five larvae from each collection were arbitrarily chosen and reared in groups of five in 25-mL cups containing 10- 15 mL of spruce budworm artificial diet (Bio-Serv Inc., Frenchtown, New Jersey) until pupation, parasitoid emergence, or death. The diet was modified for 1995 and 1996, when one or two fresh buds from an uninfested site were added to each cup containing the artificial diet in an attempt to increase the survival of first- and second-instar larvae. Diet was changed weekly. Throughout the rearing process, larvae were monitored for survival, mortality, and