Environmental Entomology (2009) 38, 971-976

Janelle G. Corn, Jim M. Story and Linda J. White (2009)
Comparison of larval development and overwintering stages of the spotted knapweed biological control agents Agapeta zoegana (Lepidoptera: Tortricidae) and Cyphocleonus achates (Coleoptera: Curculionidae) in Montana versus Eastern Europe
Environmental Entomology 38 (4), 971-976
Abstract: Larval development of insects introduced for biological control of invasive weeds may be constrained if the new climate is more extreme than in their native range. We surveyed larval development in Agapeta zoegana L. and Cyphocleonus achates (Fahraeus), two species of biological control insects introduced from eastern Europe against spotted knapweed in western North America. We dissected spotted knapweed roots collected from five sites in western Montana over 6 yr either in late fall or early spring and measured larval head capsule size to determine the overwintering instar stage. Development of A. zoegana was estimated equally well with late fall or early spring root collections, but C. achates rate of development may be underestimated using fall samples. The larvae of neither species entered diapause in as advanced an instar in western Montana as reported for their native range. Most A. zoegana larvae reached the third (26%) or fourth (20%) instar at diapause, with only 15% reaching sixth instars, as they typically do in their native Eurasia. Almost all (94%) C. achates overwintered as first instars, with most of the remaining (4%) being eggs, some of which were viable in the spring. Only a small number (2%) of C. achates larvae overwintered as second instars, the common overwintering stage in their native range. Slower development may explain, in part, why A. zoegana only has one generation per year in Montana compared with two to three generations per year in Europe.
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Link to article at publishers website
Database assignments for author(s): Janelle G. Corn, Jim M. Story

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Centaurea stoebe micranthos (weed)		U.S.A. (NW)
Cyphocleonus achates (weed bioagent)	Centaurea stoebe micranthos (weed)		U.S.A. (NW)
Agapeta zoegana (weed bioagent)	Centaurea stoebe micranthos (weed)		U.S.A. (NW)