Interactions between the parasitoid wasp Emphasis

Authors: Satoshi Koyama Michael E N Majerus

Publish Date: 2007/11/15

Volume: 53, Issue: 1, Pages: 253-264

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Abstract

The establishment spread and increase of the invasive coccinellid Harmonia axyridis Pallas in North America and Britain have coincided with declines in native ladybirds In Britain this pattern was predicted soon after H axyridis was first recorded However predictions of the impact that H axyridis may have on the parasites parasitoids and pathogens of native coccinellids have been less certain largely because of uncertainty over whether H axyridis would become an alternate host for such agents Dinocampus coccinellae Schrank is a braconid parasitoid of ladybirds of the subfamily Coccinellinae In Japan this wasp uses both Coccinella septempunctata brucki Mulsant and H axyridis as hosts but successfully parasitizes a higher proportion of the former species Data are here presented that indicate the same is true in Britain but to a greater extent This study investigates the interactions of D coccinellae with C septempunctata L and H axyridis from Japan and Britain We show that coccinellid activity affects encounter rates with the wasp with H axyridis being more active than C septempunctata in the tests Escalation rates from investigation to ovipositional attack were higher for C septempunctata than H axyridis for both Japanese and British wasps Wasp emergence was higher relative to ovipositional attack from C septempunctata than from H axyridis Wasps did not discriminate between Japanese and British ladybirds of the same species British wasp eclosion rates were higher from Japanese than from British H axyridis We consider both the effect D coccinellae may have on H axyridis population demography and the effect H axyridis may have on D coccinellae in Europe

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