Efficacy assessment of Heterorhabditis bacteriophora (Nematoda: Heterorhabditidae), Metarhizium brunneum (Hypocreales: Clavicipitaceae), and chemical insecticides for Diabrotica virgifera virgifera larval management under real farm conditions

Abstract: A two-year field study using a blend of entomopathogens in conjunction with chemical insecticides was carried out to determine to which extent they affect indigenous western corn rootworm (WCR; Diabrotica virgifera virgifera LeConte) survival, maize root damages, and grain yield. The products applied consisted of formerly in Austria registered clothianidin dressed maize seeds (Poncho®), the currently approved products Belem® (active ingredient cypermethrin) and dianem® (nematodes of the species Heterorhabditis bacteriophora), and of two innovative products based on the insect pathogenic fungus Metarhizium brunneum. The experiments were conducted in two (2013) and four (2014) naturally heavily WCR infested maize fields in the southeast of Styria, Austria. The lowest number of WCR adults was found, when the two biological control agents were combined with clothianidin dressed maize seeds. Apart from this promising result, further IPM management strategies and operational necessities aiming to bring WCR population below its stipulated economic threshold are discussed.