Responses of two entomopathogenic nematode species from the genus Steinernema to ethanol and 1-nonene

Entomopathogenic nematodes (EPNs) parasitize insects in the soil and are applied as environmentally friendly means for pest control in agriculture. Knowledge of how EPN infective juveniles (IJs) find their prey can be used to increase their effectiveness. Chemical signals in the soil are undoubtedly important but exactly which ones is little known. We hypothesized that volatile compounds emitted by EPN-infected larval cadavers could act as such signals. The objective of the study was to test the behavioral effects of 1-nonene which is known as a volatile compound emitted by several EPN-infected insect cadavers. Behavioral tests revealed that 1-nonene was attractive to IJs of both Steinernema feltiae and S. carpocapsae. High concentrations of the compound were repellent to S. feltiae and attractive to S. carpocapsae IJs. Low concentrations were attractive to S. feltiae (those from 104 to 106 times lower than the repellent concentrations) but did not affect the behavior of S. carpocapsae. Ethanol (solvent used for control tests) was attractive to S. feltiae IJs and not to those of S. carpocapsae. Both compounds are new agents involved in the behavior control of these EPN species. Different responses of IJs of two taxonomically closely related EPN species to chemical compounds could indicate interspecific difference in foraging. Behavioral reactions of S. carpocapsae IJs are more in line with the strategy of the scavenger.