Biocontrol of wireworms (Coleoptera: Elateridae) using entomopathogenic nematodes: The impact of infected host cadaver application and soil characteristics

Authors: SANDHI, RAMANDEEP KAUR - Montana State University; Shapiro Ilan, David; IVIE, MICHAEL - Montana State University; Reddy, Gadi V.P.

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2021
Publication Date: 5/24/2021
Citation: Sandhi, R., Shapiro Ilan, D.I., Ivie, M., Reddy, G.V. 2021. Biocontrol of wireworms (Coleoptera: Elateridae) using entomopathogenic nematodes: The impact of infected host cadaver application and soil characteristics. Environmental Entomology. https://doi.org/10.1093/ee/nvab042.
DOI: https://doi.org/10.1093/ee/nvab042

Interpretive Summary: Wireworms are causing economic problems in small grains and other cereal crops in Pacific Northwest. Due to the absence of effective chemical control options and harmful effects of insecticides on the environment, We explored entomopathogenic nematodes (EPNs) (Steinernema carpocapsae and Steinernema riobrave) as infected waxmoth larvae cadavers against wireworms in field and greenhouse. Moreover, effects of soil characteristics such as texture, moisture, and temperature on the infection rate of EPNs against wireworms were also studied in the laboratory. Unfortunately, in field experiments, none of the four EPN strains controlled wireworms as well as protected wheat and barley plants. However, in the greenhouse test, S. carpocapsae or S. riobrave applied in cadavers killed at least 50% of the test wireworm larvae and also protected wheat plants in the pots, when seeds were treated with imidacloprid. Synergism was observed between imidacloprid and EPNs on L. californicus mortality. Soil type and moisture levels did not have a significant effect on L. californicus mortality under laboratory conditions. However, soil temperature showed a significant effect on L. californicus mortality. Overall, imidacloprid enhanced the infection and killing ability of EPNs against wireworms and the potential of this interaction should be explored in future for better wireworm control.

Technical Abstract: Wireworms have become a significant menace to cereals in the Northern Great Plains. Therefore, research towards developing effective control methods such as biological control with entomopathogenic nematodes (EPNs) is warranted. Two strains each of two EPN species, Steinernema carpocapsae (Weiser) and Steinernema riobrave Cabanillas, Poinar, and Raulston in the form of infected Galleria mellonella (L.) cadavers were evaluated against wireworms in field and greenhouse. Additionally, effects of soil texture, moisture, and temperature on the infection rate of EPNs against Limonius californicus (Mannerheim) were examined in the laboratory. In field experiments, none of the four EPN strains were found effective against wireworms. However, in the greenhouse test, three of the strains, S. carpocapsae (All and Cxrd) or S. riobrave (355) applied in cadavers killed 50-68% of L. californicus, associated with 8-24% plant damage at 35 days after treatment (DAT), when the seeds were treated with imidacloprid. The mortality range was 40-56% with 57-75% plant damage observed at 35DAT, when seeds were planted without imidacloprid treatment. A synergistic effect among imidacloprid and S. carpocapsae (Cxrd) or S. riobrave (355) was observed in regard to L. californicus mortality. Soil type did not have a significant effect on L. californicus mortality when maintained at field capacity levels. Soil moisture also did not significantly affect L. californicus mortality. However, soil temperature showed a significant effect on L. californicus mortality. Overall, imidacloprid enhanced the infection and killing ability of EPNs against L. californicus and S. carpocapsae (All and Cxrd) strains were the virulent strains in different soil experiments.