Effect of Host Size on Susceptibility of Melanotus communis (Coleoptera: Elateridae) Wireworms to Entomopathogens

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 grain, root/ tuber, and vegetable crops. Our objectives were to characterize the pathogenicity and virulence of fungal and nematode entomopathogens on M. communis wireworms, and determine if wireworm 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 untreated control. Overall, smaller wireworms were more susceptible than larger wireworms. Our results suggested that M. communis wireworms have defenses that limit the ability of the entomopathogens we tested to infect the wireworms. Conceivably, other entomopathogen strains or species may be more effective. Natural populations of entomopathogens may contribute to wireworm population reduction, but further studies are warranted before entomopathogens can be used for M. communis management.

Evaluation of Entomopathogenic Nematodes against Common Wireworm Species in Potato Cultivation

“…As compared to other host species of EPNs, wireworms generally exhibited lower susceptibility to nematode infection, and mortality generally occurred over a longer period of time [ 37 ]. For instance, Williams et al [ 38 ] tested the efficacy of S. feltiae , S. carpocapsae , H. bacteriophora , and H. indica on the larvae of Melanotus communis (G.) at 100 Ijs/cm 2 concentration and the highest larval mortality did not exceed 15%. In another study, Forgia et al [ 39 ] conducted a laboratory bioassay against Agriotes sordidus (Illiger) larvae in well plates at 2 Ijs/cm 2 concentration and reported 8.3 and 16.7% of mortality for S. carpocapsae and H. bacteriophora strains, respectively.…”

“…Furthermore, the developmental stage of the host insect is one of the key factors affecting the pathogenicity of EPNs. Williams et al [ 38 ] reported that smaller M. communis larvae showed higher susceptibility to EPNs compared to larger wireworm larvae. Morton and Garcia-del-Pino [ 42 ] reported 75% mortality against the 5th/6th instars larvae of A. obscurus which is in line with our study.…”

Transcriptomic Analysis of Metarhizium anisopliae-Induced Immune-Related Long Non-Coding RNAs in Polymorphic Worker Castes of Solenopsis invicta

“…These include Minor (nursing), Medium (foraging), and Major (defense) [ 47 ]. Research findings suggest that the age and size of the insects can influence their vulnerability to pathogens [ 48 , 49 ]. In honey bees, immune challenges elicit different responses in nurses and foragers [ 50 ].…”