Wireworms, the larvae of click beetles, are particularly serious pest insects, as they cause considerable crop loss by feeding on roots, tubers and seedlings of various crops such as lettuce, carrots, asparagus and potatoes. Larvae of the genus Agriotes, including Agriotes lineatus, Agriotes obscurus and Agriotes sputator, pose a major threat in Europe. A promising approach is the biological control of wireworms with entomopathogenic fungi. Therefore, the effect of six Metarhizium and two Cordyceps strains on larvae of the three Agriotes species mentioned was investigated. All six Metarhizium strains were found to be pathogenic against Agriotes larvae, although the effect differed between the species. The Metarhizium brunneum strain JKI-BI-1450 was most effective against larvae of A. obscurus and A. lineatus and showed an intermediate effect against A. sputator larvae. A correlation of the efficacy of the investigated Metarhizium strains with their conidia size or germination could not be determined. Furthermore, it was examined whether the effect of two M. brunneum strains differs not only between the various Agriotes species, but also between different populations. This could be confirmed for larvae of A. obscurus, but not for A. lineatus. For A. sputator larvae, no difference in the final mortality could be determined, but in the duration from treatment to the death of the larvae.
Seib, Tanja; Reinbacher, Lara; Paluch, Maximilian; Nikolei, Robin; Lehmhus, Jörn; Grabenweger, Giselher; Stephan, Dietrich (2023): Pathogenicity of Metarhizium and Cordyceps isolates against larvae of different Agriotes species and populations in correlation with conidial size and germination. Biocontrol Science and Technology. 1-21. doi: 10.1080/09583157.2023.2294255