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Targeted dispersal of the aphid pathogenic fungus Erynia neoaphidis by the aphid predator Coccinella septempunctata
journal contributionposted on 2023-08-30, 13:25 authored by Helen E. Roy, Judith K. Pell, Peter G. Alderson
The potential of adult and larval C. septempunctata to vector the aphid-specific entomopathogenic fungus E. neoaphidis was assessed through a series of laboratory and field experiments. The ability of coccinellids to vector conidia from a colony of E. neoaphidis -infected pea aphids, Acyrthosiphon pisum, to a colony of uninfected A. pisum was demonstrated in a laboratory study. Adult coccinellids which had previously foraged on plants infested with different densities of sporulating cadavers (1, 5, 15, 30 cadavers per plant) initiated infection in a proportion of uninfected pea aphids (4, 0, 2 and 8%, respectively) when subsequently allowed to forage on A. pisum infested bean plants. Further laboratory studies demonstrated that fourth instar larvae and adult coccinellids artificially inoculated with conidia initiated 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 which had previously been foraged on by inoculated larval and adult coccinellids also died from infection (3 and 10% of A. pisum, respectively). However, although coccinellid adults inoculated with conidia initiated infection in 19% of A. pisum, cereal aphids, S. avenae , exposed to the inoculated coccinellids did not become infected. A further laboratory study demonstrated that infection of A. pisum only occurred if inoculated coccinellids were transferred to A. pisum populations immediately post inoculation. However, a proportion of A. pisum placed on bean plants which had been foraged on by inoculated coccinellids transferred 0, 4 and 24 h post inoculation died from infection (9, 3 and 7%, respectively). A field study further demonstrated the potential of coccinellids to vector E. neoaphidis. Single spring sown field bean plants (Long Hoos Experimental Plots, IACRRothamsted Farm) were enclosed within nylon mesh bags and 25 adult A. pisum were added to each bag with one of the following treatments: no further addition (control), coccinellid adult (control), inoculated coccinellid adult, inoculated A. pisum or sporulating A. pisum cadavers. No aphids died of E. neoaphidis in the control treatments; 5, 16 and 33% of aphids were infected with E. neoaphidis on the other treatments, respectively.
Publication titleBiocontrol Science and Technology
PublisherTaylor & Francis