Faculté des sciences

Parasitism of non-target lepidoptera by mass released Trichogramma brassicae and its implication for the larval parasitoid Lydella thompsoni

Kuske, Stefan ; Babendreier, Dirk ; Edwards, Peter ; Turlings, Ted C. J. ; Bigler, Franz

In: BioControl, 2004, vol. 49, no. 1, p. 1-19

The release of high numbers of the eggparasitoid Trichogramma brassicae Bezd.(Hym. Trichogrammatidae) to control the European corn borer (ECB), Ostrinianubilalis Hb. (Lep.: Crambidae) in maize hasraised concerns about potential negativeeffects on native natural enemies. The nativelarval parasitoid Lydella thompsoni Herting (Dipt.: Tachinidae) is the most frequent and... Plus

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    Summary
    The release of high numbers of the eggparasitoid Trichogramma brassicae Bezd.(Hym. Trichogrammatidae) to control the European corn borer (ECB), Ostrinianubilalis Hb. (Lep.: Crambidae) in maize hasraised concerns about potential negativeeffects on native natural enemies. The nativelarval parasitoid Lydella thompsoni Herting (Dipt.: Tachinidae) is the most frequent and important ECB parasitoid insouthern Switzerland and can achieve highparasitism rates. Its first generation emerges too early to find ECB larvae and must rely onalternative hosts living in natural habitats close to maize fields. Inundative releases of T. brassicae coincide with the oviposition period of the alternative hosts ofthe tachinid. T. brassicae moving out of release fields may attack and diminish the population of these hosts, creating abottleneck situation for L. thompsoni in the subsequent spring. Laboratory hostspecificity tests showed that the tachinid's two most abundant spring hosts Archanarageminipuncta Haworth (1809) (Lep.: Noctuidae)and Chilo phragmitellus Hübner (1805)(Lep.: Crambidae) are successfully parasitisedby T. brassicae females in no-choice situations. Our extensive field surveys, however, showed that the two tested springhosts escape parasitism since their eggs are well hidden or not attractive. Negative effects of inundative releases of T.brassicae on the native tachinid fly L. thompsoni, such as population density reduction, displacement, or local extinction, are very unlikely.