Enhancement of spores dissemination in the combination of entomopathogenic nematodes and fungus

Abstract

Entomopathogenic nematodes and fungi are organisms that cause epizootics in insect and are therefore important bioagents. 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 may enhance their efficacy against host and the nematodes can disseminate fungal spores on cuticle. We focused on evaluating the effects of foraging behaviour of Steinernema feltiae, Heterorhabditis bacteriophora, and Steinernema carpocapsae on the dissemination of Cordyceps fumosorosea. 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 experimental designs: soil-filled glass tubes and soil columns. The latter experiment also used alginate and sunflower oil as adhesives to explore ways to enhance spore dispersal.Results illustrated that nematodes improve the transmission of C. fumosorosea spores; particularly conidia. The nematodes 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 oil was determined to be the most successful adhesive medium and increased spore distribution for all tested nematodes.These findings indicate the potential use of adhesives in biocontrol to enhance nematode dissemination of EPF spores. Additional research regarding adhesives, as well as the mechanisms of spore adhesion to the nematode may be of importance in the future.