Click-beetle species and biological control of wireworms

Wireworms, the larval stages of click beetles, cause feeding damage to a number of crops. With potatoes the tuber quality is frequently impaired, leading to downgrading losses. In Switzerland damage north of the Alps is primarily caused by the Agriotes obscurus, A. lineatus and A. sputator species. All three species have a very similar cycle of life. The period of development from egg to adult beetle lasts three to five years. With persistent warming the cycle is more and more often reduced to three years. Flight monitoring with pheromone traps from 2005 to 2007 has shown that the three species are represented with different densities in different regions. A. lineatus and A. sputator now predominate in several regions instead of the previously most frequently observed species A. obscurus. Most of the beetles were trapped during warm weather from late April to late May. The use of the insect pathogenic fungus Metarhizium anisopliae is being investigated for the biological control of the wireworms. To date, there has been no success in isolating a suitable strain of fungus capable of reducing the wireworm population in the short term. In the longer term, however, there are prospects of controlling the harmful wireworms to a tolerable extent with a suitable isolate of M. anisopliae.