Metarhizium is the message – new IPM strategy to control larvae and adults of Diabrotica v. virgifera

Abstract: The number of Diabrotica v. virgifera beetles caught in South-East Styria has continuously increased since 2001. In 2018, up to 130 beetles/m2 were caught with an established emergence trap system in untreated maize fields. This represents a triplication of the number of adults caught in 2017 and an increase of almost 500 percent compared to 2016. The goal of this study was to test efficacy of Metarhizium brunneum (GranMet-PTM, Agrifutur s.r.l.) used to control D. v. virgifera larvae in the field. The inundative mass application of the biological control agent (BCA) led to a significant reduction of the number of Diabrotica larvae compared to untreated control fields. The targeted abundance of 5,000 M. brunneum CFU/g soil dry wt was achieved or even exceeded after the first application of the fungal barley product GranMet-PTM. Genotyping with SSR markers confirmed that the Metarhizium production strain was able to establish in the treatment areas. Due to the lack of environmentally friendly, approved chemical insecticides (neonicotinoid ban in Europe), a direct control of the adult beetles with biological active substances is essential. Using a water-dispersible Metarhizium formulation, we were able to demonstrate for the first time that the biological control of adult beetles appears possible.