Effect of host size on susceptibility of melanotus communis (coleoptera: elateridae) wireworms to entomopathogens

Authors: Williams, Livy; CHERRY, RON - University Of Florida; Shapiro Ilan, David

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2022
Publication Date: 9/29/2022
Citation: Williams III, L.H., Cherry, R., Shapiro Ilan, D.I. 2022. Effect of host size on susceptibility of melanotus communis (coleoptera: elateridae) wireworms to entomopathogens. Journal of Nematology. 54(1):3922. https://doi.org/10.2478/jofnem-2022-0033.
DOI: https://doi.org/10.2478/jofnem-2022-0033

Interpretive Summary: Pathogens that live in the soil have been used to manage soil-borne crop pests for decades. These pathogens are safe to humans, environmentally benign, and are amenable to commercial production and field application. In the eastern U.S., a pestiferous soil-borne insect, commonly called the corn wireworm, is a serious pest of potatoes, vegetables, sugar cane, grains, and sweetpotatoes. The goal of this study was to characterize the effect of fungal and nematode pathogens on the corn wireworm, and determine if wireworm size affected mortality. We tested five nematodes and two fungi in laboratory bioassays. None of the pathogens killed more than 15% of the wireworms when assessed at 7 and 14 days after exposure. Overall, smaller wireworms were more susceptible than were larger wireworms. Our results suggested that the corn wireworm has defenses that limit the ability of the pathogens we tested to infect the wireworms. Naturally-occurring populations of these pathogens may contribute to wireworm control (particularly smaller wireworms) albeit not as major regulatory factors. Inundative biological control applications of the pathogens tested are not likely to be economically viable. Instead, other pathogen strains or species that have a closer host-pathogen relationship should be identified for future study.

Technical Abstract: Wireworms, the soil-borne larvae of click beetles (Coleoptera: Elateridae), are important crop pests throughout the world. In the eastern U.S., Melanotus communis larvae attack numerous crops such as corn, sugarcane, potatoes, vegetables and sweet potatoes. Our objectives were to characterize the pathogenicity and virulence of fungal and nematode entomopathogens on M. communis wireworms, and determine if host size affected virulence. Pathogens tested included five entomopathogenic nematodes, Steinernema carpocapsae (All strain), S. feltiae (SN strain), S. riobrave (355 strain), Heterorhabditis bacteriophora (VS strain), and H. indica (HiHom1 strain); and two entomopathogenic fungi, Beauveria bassiana (GHA strain) and Cordyceps javanica (WF-GA17 strain). None of the pathogens tested caused >15% mortality at 7 or 14 days post-inoculation. Mortality was highest in S. carpocapsae (All strain); the other entomopathogens did not cause higher mortality than the non-treated control. Overall, smaller wireworms were more susceptible than were larger wireworms. Our results suggested that M. communis wireworms have defenses that limit the ability of the entomopathogens we tested to infect the wireworms. Natural populations of these entomopathogens may contribute to wireworm population reduction (particularly early instars) albeit not as major regulatory factors. Inundative biological control applications of the entomopathogens tested are not likely to be economically viable. Conceivably, other entomopathogen strains or species may be more effective.