Interaction of the wireworm species Agriotes obscurus, A. sputator and A. lineatus with a new granule formulation of Metarhizium brunneum

The attract-and-kill strategy is a promising approach in integrated pest management to increase the efficiency of plant protection products by pushing the required contact between target pest and active ingredient. Within the project AgriMet, a new soil granule of the entomopathogenic fungus Metarhizium brunneum was developed to control wireworms of the genus Agriotes (Coleoptera: Elateridae) in potato cultivation. The formulation is based on autoclaved millet as a substrate to lure the larvae to the infectious conidia on its surface. However, no data existed about the interactions of wireworms with the AgriMet-Granule. Here, I examined the behavioural response of the wireworm species A. obscurus, A. sputator and A. lineatus to the AgriMet-Granule using an olfactometric bioassay in the laboratory. The foraging behaviour of A. obscurus and A. sputator, with regard to the AgriMet-Granule, was tested with a feed-choice-experiment using a horizontal arena set-up. The tested wireworms significantly preferred autoclaved millet compared to the control. Fungal colonisation on the surface of the AgriMet-Granule did not influence their preference in general. However, differences were observed depending on the respective wireworm species and the two Metarhizium spp. isolates used. The feeding bioassay showed that the acceptance of wireworms for the AgriMet-Granule, with a low conidia concentration on its surface, was high. A high conidia concentration on the surface of the AgriMet-Granule led to a decreased acceptance that differed between the wireworm species. However, the survival analysis of wireworms isolated after the feed choice experiment indicated that the wireworms came in contact with the infectious conidia. Overall, the data suggests that autoclaved millet is a suitable substrate for the AgriMet-Granule. It attracts larvae of the genus Agriotes to the biocontrol agent using the formulated M. brunneum isolate.