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Ascaroside pheromones stimulate dispersal, a key nematode behavior to find a new food source. Ascarosides produced by entomopathogenic nematodes (EPNs) drive infective juvenile (IJ) emergence from consumed cadavers and dispersal in soil. Without ascarosides from host cadavers, Steinernema feltiae (EPN) reduce dispersal substantially. To determine whether other Steinernema spp. exhibit the same behavior, we compared S. feltiae and S. carpocapsae IJs without host cadaver pheromones. Unlike S. feltiae, S. carpocapsae IJs continued to disperse. However, S. carpocapsae IJs exhibited a temperature-dependent quiescent period. The IJ quiescent period increased at ≤20 °C but did not appear at ≥25 °C. Consistent with this, S. carpocapsae IJ quiescence increased from 30 min to 24 h at ≤20 °C over 60 days. The quiescent period was overcome by dispersal pheromone extracts of their own, other Steinernema spp. and Heterorhabditis spp. Furthermore, S. carpocapsae IJ ambush foraging associated behaviors (tail standing, waving, and jumping) were unaffected by the absence or presence of host cadaver pheromones. For S. feltiae, IJ dispersal declined at all temperatures tested. Understanding the interaction between foraging strategies and pheromone signals will help uncover molecular mechanisms of host seeking, pathogenicity and practical applications to improve the EPN's efficacy as biocontrol agents. Dispersing and host-finding are important behaviors for parasites' success; finding a new host involves emergence from the host, dispersal, and foraging for a new host. A combination of intrinsic chemical drivers and extrinsic cues associated with potential hosts drives dispersal, searching behaviors and infection decisions. Local environmental conditions also affect parasites' success. For example, for soil-associated parasites these environmental factors include soil type, soil moisture, salinity, and temperature, among others. Entomopathogenic nematodes (EPN) in the genera Heterorhabditis and Steinernema are insect parasites used as model organisms to study the biology of parasites 1,2. Since they kill insects, they also have commercial applications for controlling insect pests as biocontrol agents 3-5. Once EPNs consume an insect host a specialized non-developmental life stage, called the infective juvenile (IJ), emerges from the spent host and disperses to search for a new host. The IJs carry tens to hundreds of symbiotic bacteria cells (Xenorhabdus spp. for Steinernema spp. nematodes and Photorhabdus spp. for Heterorhabditis spp. nematodes). Once a host has been infected by multiple IJs, the nematodes resume development, release their symbiotic bacteria, feed on the bacteria, and one to three generations develop within a single host over a 10 to 22-day period. When nutritional quality declines and waste products increase, IJs once again develop and emerge from the host. The EPN IJ host finding process

There are many types of drippers with different flow path length, flow path shape and filtration surface. EPN delivery performance of the most commonly used four different types of drippers (in-line short path, in-line long path, in-line cylindrical and on-line button) was examined with a drip irrigation system in laboratory conditions. Under four different pressures (0.5, 1, 1.5, 2 bar), EPNs were applied to 1-liter beakers with irrigation system and discharged nematodes were counted under a stereomicroscope. The effect of pressure on application and EPN mortality were also determined. The results showed that there were significant differences between the discharge ratio of EPNs from drippers. Among the four drippers, on-line button dripper sustained the highest and fastest discharge ratio. Pressure alone had no significant effect on delivering EPNs. However, it should be considered that long pressure exposure may harm EPNs. Regarding our results, different irrigation drippers have significantly different effects on EPN discharge ratio. Therefore, optimizing drip irrigation systems for EPN applications may increase their performance.

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