Are entomopathogenic nematodes (Steinernema and Heterorhabditis) compatible with acaricides?

Abstract: Entomopathogenic nematodes (EPNs) are organisms that can be used in biological control programmes. To expand our knowledge about the compatibility of EPNs to pesticides, we studied the compatibility of EPNs infective juveniles (IJs) to five acaricides under laboratory conditions. The direct exposure of acaricides to EPNs was studied in Petri dishes at 15, 20, and 25 °C. EPNs were exposed to acaricides for 1, 4, and 24 hours. Four EPNs species were included in our investigation: Steinernema feltiae, S. carpocapsae, S. kraussei, and Heterorhabditis bacteriophora. The results of our laboratory investigation showed that H. bacteriophora was the most tolerant EPN species. On the other hand, the most sensitive EPN species was S. feltiae. Our observations showed that S. feltiae can be mixed with only two acaricides. The active ingredient fenpyroximate proved to be the most suitable for mixing with EPNs. Our results showed that fenpyroximate was only lethal to S. feltiae (44% mortality) at 25 °C. The mortality of EPNs was highest in the active ingredients abamectin and pyrethrin. Our results confirmed that the compatibility of EPNs to acaricides is a species specific characteristic. The mortality of EPNs was also influenced by the exposure time, active ingredient, and temperature. The combined use of EPNs and acaricides could represent an advantage in integrated plant protection programmes. Combinations of EPNs and acaricides could save time and money in the simultaneous control of various pests (insects, mites) in glasshouses.