Abstract
Efficacy of the Metarhizium brunneum Petch (Hypocreales: Clavicipitaceae) strain ART2825 for control of wireworms (Agriotes obscurus (L.), Coleoptera: Elateridae) was examined in a semi-field pot experiment. Pots were treated in late summer during sowing of spring oat as a cover crop. Survival of wireworms was assessed four weeks after their release in October 2013, and 30 weeks after release in April 2014. Viability and persistence of the fungus was determined by counting colony forming units from substrate samples and microsatellite analyses of recovered Metarhizium isolates. The number of colonies detected in the substrate in October 2013 increased with increasing concentrations of applied conidia, and no significant reduction was observed at the second evaluation date in April 2014. Increasing conidia application rates significantly increased mycosis and reduced wireworm survival, to a level comparable to that of treatment using insecticide-coated oat seeds. The preventive application of M. brunneum conidia to reduce wireworm populations in cover crops, preceding a damage-sensitive crop like potatoes, may be a promising biocontrol strategy.
Highlights
Wireworms are the soil dwelling larvae of click beetles (Coleoptera: Elateridae) and several species, including those in the genus Agriotes Eschscholtz, are major pests in the northern hemisphere
Conidia harvested from Petri dishes were used for massproduction of fungus colonised barley kernels (FCBKs) (Aregger 1992)
0.014 0.008 \0.001 0.366 at the second evaluation date, five Metarhizium isolates were randomly chosen from substrate samples of the untreated control and four isolates from the insecticide treatment, to check for the natural presence of the M. brunneum strain applied during the experiment
Summary
Wireworms are the soil dwelling larvae of click beetles (Coleoptera: Elateridae) and several species, including those in the genus Agriotes Eschscholtz, are major pests in the northern hemisphere They feed on the roots, shoots, tubers and bulbs of many arable and vegetable crops, including maize and other cereals, potatoes and carrots (reviewed in Parker and Howard 2001; Ritter and Richter 2013; Traugott et al 2015). Pre-planting of organochlorine-coated wheat seeds as a catch crop before planting of potatoes has been shown to reduce wireworm damage to potatoes in experiments in Canada (Vernon et al 2016) This control strategy was later abandoned when the insecticide was de-registered. We assessed the influence of treatments with M. brunneum conidia on recapture, survival and mycosis of previously released wireworms
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