Efficacy of entomopathogenic nematodes against the sugarbeet wireworm, Limonius californicus (Mannerheim) (Coleoptera: Elateridae)

Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), are economically important soil-dwelling pests that attack many field crops worldwide. Wireworms have become a serious threat to spring wheat in the Northern Great Plains because of lack of effective control measures, creating a need for alternative control methods such as biological control with entomopathogenic nematodes (EPNs). A laboratory bioassay was used to test ten EPN strains and identify infective EPN strains against the sugarbeet wireworm, Limonius californicus (Mannerheim) (Coleoptera: Elateridae). Steinernema carpocapsae (Weiser) (All and Cxrd strains) and S. riobrave Cabanillas, Poinar, and Raulston (355 and 7-12 strains) killed 60-70% of L. californicus larvae in four weeks when applied at 700 Infective juveniles (IJs) (25 IJs/cm(2)), 1400 IJs (50 IJs/cm(2)), 2800 IJs (100 IJs/cm(2)), and 5600 IJs (200 IJs/cm(2)) per larva in the laboratory. Also, Heterorhabditis bacteriophora (Poinar) VS strain and Steinernema rarum (Doucet) 17c + e strain caused 50-60% mortality to L. californicus larvae after four weeks when applied at 5600 IJs/larva. However, regardless of the concentration applied, the penetration rate of infective juveniles into the host did not exceed 33%. In shade house trials, S. riobrave and S. carpocapsae strains caused 34-56% L. californicus mortality after four weeks with 50 and 56% mortality caused by S. carpocapsae All and S. riobrave 355 strain, respectively when applied at the rate of 80,000 IJs/pot. These results suggest that S. carpocapsae and S. riobrave may have significant potential for protecting spring wheat crops from L. californicus.