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

Authors: SANDHI, RAMANDEEP - Montana State University; Shapiro Ilan, David; SHARMA, ANAMIKA - Montana State University; Reddy, Gadi V.P.

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2020
Publication Date: 1/11/2020
Publication URL: https://handle.nal.usda.gov/10113/6810984
Citation: Sandhi, R.K., Shapiro Ilan, D.I., Sharma, A., Reddy, G.V. 2020. Efficacy of entomopathogenic nematodes against the sugarbeet wireworm, Limonius californicus (Mannerheim) (Coleoptera: Elateridae). Biological Control. 143. https://doi.org/10.1016/j.biocontrol.2020.104190.
DOI: https://doi.org/10.1016/j.biocontrol.2020.104190

Interpretive Summary: Wireworms, the soil inhabiting larval stages of click beetles, are significant pests of cereal and other field crops in Montana especially the Golden Triangle region of Montana because of their cryptic behavior in soil. There are no effective control measures available for wireworms. Seed treatments with neonicotinoid pesticides can only repel the wireworms temporarily. Therefore, studies toward the development of alternative wireworm management tactics are required. Entomopathogenic nematodes, also called beneficial nematodes, kill insect pests and are considered environmentally-friendly natural control agents. A laboratory bioassay was used to test ten entomopathogenic nematodes strains and identify infective strains against the sugarbeet wireworm (Coleoptera: Elateridae). The nematodes named Steinernema carpocapsae and S. riobrave produced high levels of mortality (60-70%) in wireworms in four weeks when applied at 700-5600 nematodes in the laboratory. In shade house trials, both nematode species were able to kill at least 50% of the treated wireworm larvae. These results suggest that S. carpocapsae and S. riobrave may have significant potential for protecting spring wheat crops from sugarbeet wireworms.

Technical Abstract: 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 a lack of effective control measures, creating a need for alternative control methods such as biological control such as 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 IJs (25 IJs/cm2), 1400 IJs (50 IJs/cm2), 2800 IJs (100 IJs/cm2), and 5600 IJs/larva (200 IJs/cm2) 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.