38th Annual Meeting of the Society for Invertebrate Pathology

A wide variety of abiotic factors can affect the ability of infective juveniles (IJs) of entomopathogenic nematodes to find and infect insect hosts and survive in agroecosystems. Among environmental factors, temperature and moisture (relative humidity and free water) are the best studied and are the most influential factors that limit or enhance activity of IJ. Their effects are most pronounced on foliage and other exposed habitats. The efficacy of one of the most widely utilized EPN species, Steinernema carpocapsae, begins to decline at 15°C and comes to a complete standstill at 10°C. Species such as S. feltiae, S. kraussei, and some of the heterorhabditid species are active at lower temperatures (5-10°C), but may be inhibited at higher temperatures. The opposite is the case for S. riobrave. Adequate moisture is critical for the movement and survival nematodes. Water applied after application of IJs is also needed to help penetrate barriers (foliage, thatch, etc.). Exposure to ultraviolet light and extremes of pH can also affect IJ survival. Abiotic factors in the application of IJs (friction and pressure) can have detrimental effects on the viability and vigor of IJs. Small nematodes, such as S. carpocapsae and Heterorhabditis bacteriophora can withstand spray system pressures up to 2000 kPa whereas with larger species, such as H. megidis, the pressures within the spray system should not exceed 1380 kPa. The friction produced within the spray system, particularly the nozzles, swirl plates and filters could also have detrimental effects on IJs. Physical barriers and agrochemicals and other agricultural practices can also influence IJ infectivity and survival.