D3172: Impact of entomopathogenic nematodes on mortality of the western corn rootworm under laboratory conditions

Diabrotica virgifera virgifera, commonly known as western corn rootworm (WCR), is one of the most damaging pests affecting corn production. This pest has developed resistance to several control methods such as: Bt maize, crop rotation, and insecticides. Thus, the use of entomopathogenic nematodes (EPNs) can be another control measure taken against this pest. This study evaluated the effectiveness of EPNs in controlling WCR under laboratory conditions. Commercial strains of Steinernema feltiae and Heterorhabditis bacteriophora from Persistent Biocontrol, Koppert, and Arbico Organics, as well as a non-commercial field-collected strain of Steinernema carpocapsae from South Dakota were tested. EPN treatments were applied to cups (118 ml) containing five corn seedlings in a 1:1 mixture of sterile soil and sand at two concentrations (135.85 million and 2 billion infective juveniles/ha). Cups were infested with five third-instar WCR larvae. After seven days, larval mortality was assessed. To confirm EPN infection, White traps were set up. A second experiment was conducted using Galleria mellonella larvae following the same methodology, but without corn seedlings. At the higher concentration, H. bacteriophora (Arbico Organics) caused the highest infection in WCR, followed by H. bacteriophora (Koppert) and S. carpocapsae (South Dakota). The increase in concentration did not result in an increase in WCR infection, except for H. bacteriophora (Arbico Organics). For G. mellonella, most EPNs caused around 100% larval infection at both concentrations. These findings provide insights into selecting EPN sources, species, and concentrations for WCR management in future field studies.