Chemical-based strategies to control the western corn rootworm, Diabrotica virgifera virgifera Le Conte

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is one of the most severe pests of cultivated maize, Zea mays L. Most of the damage to this crop is caused by larvae feeding on the root system, causing important economic costs in terms of yield losses and management efforts. This research was carried out to evaluate the effect of different chemical control strategies to minimize larval damage in maize fields under natural infestation of the pest. Field-based research was performed in a two-year period (2011–2012) in five locations of northern Italy. Different insecticide strategies (belonging to the pyrethroid, neonicotinoid or organophosphate classes) were compared to an untreated control. The effects on larval infestation, root damage, silage and grain yield were assessed. Our data highlighted that insecticide application at sowing led to a significant reduction in the WCR larval density, both considering insecticide seed treatments and in-furrow soil applications. In particular, seed-applied clothianidin (systemic) and tefluthrin (non-systemic) applied at sowing led to a maximum increase in grain yield of 18% and 19% respectively, when compared to the untreated control. In all the surveyed plots, limited plant lodging was observed. Furthermore, while the silage yield did not significantly differ among untreated and treated plots, significant differences were recorded with regard to grain yield. No significant results occurred with the liquid insecticide applied in the intra-row space at ridging, with regard to reduction in WCR larval density and grain yield.