Pheromone traps for the dissemination of an entomopathogen by the Damson-hop aphid Phorodon humuli

Two types of sex pheromone-emitting trap, a simple louvred trap and a commercially-produced wasp trap (Waspy(R)) designed or modified as delivery systems for entomopathogens, were tested using an isolate of the pathogen Verticillium lecanii. Their efficiencies for capturing winged autumn females (gynoparae) and males of Phorodon humuli in a hop garden and a plum orchard were compared with each other and with catches by yellow-painted water traps. Gynoparae rarely entered either type of pathogen dissemination trap. Males only entered traps that released (1R,S,4aR, 7S, 7aS)-nepetalactol, the sex pheromone of P. humuli. In the hop garden, approximately five times as many males entered the modified Waspy(R) as entered the louvred traps whereas in the plum orchard similar numbers of males were caught in both traps. On average, males visited the modified Waspy(R) trap for 34.1 +/- 7.9 (SE) min. Males spent about 50% of their time in the arena where the entomopathogen would normally be present and a further 20% of the time on the inside of the arena lid alongside the pheromone source. Out of a sample of 16 live aphids removed from a trap dispensing V. lecanii, 9 died from infection by the pathogen and 5 of the 16 initiated colonies of the fungus after they walked on a sterile agar plate for Jive minutes. None of the 15 aphids collected from traps without V. lecanii became infected or initiated colonies of the fungus on agar plates.