Integrating parasitoids into management of pollen beetle onoilseed rape
Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ,UK
Abstract:
Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ,UK Hymenopterous parasitoids can exert substantial natural control on oilseed rape pest populations. This paper reviews recent work at Rothamsted Research on integrating parasitoids into the management of rape pests. It focuses on the pollen beetle, Meligethes aeneus, and its two larval endoparasitoids, Phradis interstitialis and Tersilochus heterocerus. Strategic research on the behavioural ecology of the parasitoids is described. Phradis interstitialis was shown to use upwind anemotaxis to locate the crop. Within-field spatio-temporal distributions of M. aeneus adults and larvae were complex with irregular patterns of aggregation. Whereas P. interstitialis was closely associated temporally and spatially with the distribution of its host, T. heterocerus larvae were as abundant outside dense host patches as within them and showed little pattern. Both parasitoid species overwinter in the soil of the rape field and emerge the following spring. Post-harvest soil cultivations, particularly ploughing, can reduce their survival, whereas non-inversion tillage is less harmful. Phenological studies show that pyrethroid applications during flowering threaten parasitoid populations. Implications of the research for conservation biological control and the development of more environmentally-friendly crop protection is discussed.
Key words:
conservation biological control, Meligethes aeneus, parasitoids