Conservation biological control with the fungal pathogen Pandora neoaphidis : implications of aphid species, host plant and predator foraging

1 Pandora neoaphidis is an important aphid-specific fungal pathogen in temperate agroecosystems. Laboratory studies were carried out to obtain baseline data on factors that may affect its performance in conservation biological control. 2 Virulence of P. neoaphidis was assessed in dose-response bioassays against Microlophium carnosum on nettle, Uroleucon jaceae on knapweed, Acyrthosiphon pisum on bean and bird's-foot trefoil Lotus corniculatus, and Metopolophium dirhodum on barley and Yorkshire fog Holcus lanatus. The most susceptible aphid was A. pisum feeding on bean with an LD50 of 19 conidia per mm(2), whereas U. jaceae had an LD50 of 104 conidia per mm(2) and was least susceptible to infection. 3 The presence of foraging adult ladybirds, Coccinella septempunctata, increased transmission of P. neoaphidis from infected cadavers to apterae of M. carnosum, U. jacea, and A. pisum by 7-30% at the largest cadaver density tested. Adult coccinellids that had previously foraged on nettle, knapweed, bean or bird's-foot trefoil transfered conidia to A. pisum on bean and induced infections in 2-13% of aphids. 4 Conidia of P. neoaphidis dispersed passively in the airstream from sporulating M. carnosum cadavers on nettle plants and initiated infections in A. pisum colonies feeding on bean (4-33%) or M. dirhodum on barley (3%) located within 1.0 m of the nettle source. 5 The results suggest that M. carnosum and A. pisum may be more useful as reservoirs for P. neoaphidis in noncrop and crop areas than U. jaceae or M. dirhodum, and infection and dispersal between habitats could be enhanced in the presence of coccinellids.