An attract and kill tactic for click beetles based on Metarhizium brunneum and a new formulation of sex pheromone

Abstract

Wireworms are a serious agricultural pest, with control efforts targeting soil-dwelling larvae almost ex- clusively. They appear yearly for a brief period as adult click beetles to mate and oviposit, and as adults, possess qualities that make them good candidates for an attract and kill control tactic: (i) susceptibility to certain ento- mopathogenic fungi; and (ii) attraction of males to female sex pheromones. To expand the range of wireworm control options, our study aimed to determine if banded applica- tions of a new granular formulation of Agriotes obscurus L. (Coleoptera: Elateridae) pheromone would increase beetle mortality when applied with banded Metarhizium brun- neum Petch (Ascomycota: Hypocreales: Clavicipitaceae) LRC112. Pheromone granules applied at 12.7 kg/ha (1 % wt/wt 1:1 geranyl hexanoate:geranyl octanoate) together with rice conidiated with 2 9 10 14 conidia/ha of M. brunneum LRC112 reduced beetle recapture by 98.2 % compared to M. brunneum alone. A lower rate (2 9 10 13 conidia/ha) of M. brunneum with pheromone granules re- duced recapture by 82.6 % compared to the lower rate alone. A significantly greater number of beetles aggregated at pheromone bands to acquire lethal doses of conidia in as little as 6 h, with conidia dose remaining unchanged up to 54 h later. Conidia dose acquired by beetles corresponded to treatment and was positively related to total beetle mortality and speed of death. Attracting and killing click beetles might represent a new tactical approach to control wireworm larvae by reducing click beetle fecundity. We expect the pheromone granules to also to have utility for click beetle mating disruption.