Enhancement of spores´ dissemination by entomopathogenic nematodes

Abstract: Entomopathogenic nematodes and entomopathogenic fungi are soil organisms that cause epizootics in insect pests and are therefore important agents in pest management and biocontrol. Many studies focus on the effectiveness of either entomopathogenic nematodes or fungi for controlling pests, though it has been shown that a combination of the two entomopathogens enhances their efficacy against targeted host insects. We focused on evaluating the effects of foraging behaviour of Steinernema feltiae, Heterorhabditis bacteriophora, and Steinernema carpocapsae on the dissemination of Cordyceps fumosorosea spores. Additionally, we investigated how the nematode’s 2nd stage cuticle as well as various adhesives impact spore transmission. Fungal dispersal via nematodes was studied through two different experimental designs: soil-filled glass tubes and soil columns. The soil column experiment also used liquid alginate and sunflower seed oil as adhesives to explore ways to enhance spore dispersal. Results illustrated that entomopathogenic nematodes improve the transmission of C. fumosorosea spores; particularly conidia show a higher distribution. The nematode strains S. feltiae and S. carpocapsae were found to spread spores most effectively, depending however on the experimental soil conditions. Research revealed that the nematode’s 2nd stage cuticle is an important factor for spore dispersal; without it, transmission rates drop significantly. Sunflower seed oil was determined to be the most successful adhesive medium and increased spore distribution for all tested nematode strains. These findings indicate the potential use of adhesives in pest management to increase efficacy. Additional research regarding adhesives, as well as the mechanisms of spore adhesion to the nematode cuticle may be of importance in the future.