Targeted dispersal of the aphid pathogenic fungus Erynia neoaphidis by theaphid predator Coccinella septempunctata

The potential of adult and larval C. septempunctata to vector the aphid-spe cific entomopathogenic fungus E. neoaphidis was assessed through a series o f laboratory and Weld experiments. The ability of coccinellids to vector co nidia from a colony of E. neoaphidis-infected pea aphids, Acyrthosiphon pis um, to a colony of uninfected A. pisum was demonstrated in a laboratory stu dy. Adult coccinellids which had previously foraged on plants infested with different densities of sporulating cadavers (1, 5, 15, 30 cadavers per pla nt) initiated infection in a proportion of uninfected pea aphids (4, 0, 2 a nd 8%, respectively) when subsequently allowed to forage on A. pisum infest ed bean plants. Further laboratory studies demonstrated that fourth instar larvae and adult coccinellids artificially inoculated with conidia initiate d infection in 11 and 13% of an A. pisum population in which they foraged, respectively. Furthermore, a proportion of A. pisum placed on bean plants w hich had previously been foraged on by inoculated larval and adult coccinel lids also died from infection (3 and 10% of A. pisum, respectively). Howeve r, although coccinellid adults inoculated with conidia initiated infection in 19% of A. pisum, cereal aphids, S. avenae, exposed to the inoculated coc cinellids did not become infected. A further laboratory study demonstrated that infection of A. pisum only occurred if inoculated coccinellids were tr ansferred to A. pisum populations immediately post inoculation. However, a proportion of A. pisum placed on bean plants which had been foraged on by i noculated coccinellids transferred 0, 4 and 24 h post inoculation died from infection (9, 3 and 7%, respectively). A Weld study further demonstrated t he potential of coccinellids to vector E. neoaphidis. Single spring sown We ld bean plants (Long Hoos Experimental Plots, IACR-Rothamsted Farm) were en closed within nylon mesh bags and 25 adult A. pisum were added to each bag with one of the following treatments: no further addition (control), coccin ellid adult (control), inoculated coccinellid adult, inoculated A. pisum or sporulating A. pisum cadavers. No aphids died of E. neoaphidis in the cont rol treatments; 5, 16 and 33% of aphids were infected with E. neoaphidis on the other treatments, respectively.