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Turkish Journal of Zoology

DOI

10.3906/zoo-2103-47

Abstract

Wireworms (Agriotes obscurus, Agriotes lineatus, Agriotes sordidus) are major pests of arable crops. Damage caused by these subterranean pests has increased following the withdrawal of many traditional synthetic insecticides. Wireworms are susceptible to entomopathogenic fungi belonging to the genus Metarhizium. The aim of this study was to determine if exposure of different wireworm species to sublethal doses of the insecticide spinosad altered their susceptibility to different strains of Metarhizium brunneum. Of the three wireworm species studied, A. obscurus was the most susceptible species to the isolates of M. brunneum tested, while A. lineatus and A. sordidus were not affected by the entomopathogen on its own. However, combination of spinosad and M. brunneum could cause significant mortality and, depending on the treatment combination, some interactions were determined as being either antagonistic, additive or synergistic. The efficacy of the stress-and-kill strategy was dependent on the fungal strain, insect species, dose of stressing agent and time. M. brunneum strain F52 and ART2825 combined with low doses of spinosad resulted in a synergistic reaction. Scanning electron microscopy shows that without spinosad, poor germination was seen on the wireworm cuticle, indicating that it could be fungistatic. However, the increased susceptibility of the wireworms to the stress-and-kill seem to indicate physiological changes due to spinosad, facilitating germination and penetration of the fungi. Our results show that stress-and-kill can provide wireworm control; yet, the right combination between the fungi, stressing agent and insect species is mandatory.

First Page

395

Last Page

407

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