Screening adjuvants for use in spray solutions of entomopathogenic nematodes through different parameters: EPN survival, infectivity, sedimentation speed and leaf deposition

Due to more stringent regulations on pesticides, biological alternatives for pest control are gaining popularity. Entomopathogenic nematodes (EPN) are a promising biological alternative to conventional insecticides. However, EPN are not always equally effective due to environmental factors like temperature, humidity and sunlight. The inclusion of adjuvants in the spray liquid has proven to enhance the effectiveness of EPN in various crops. This paper proposes a selection procedure for spray adjuvants that are to be used for outdoor applications of entomopathogenic nematodes. The selection procedure tests the effect of adjuvants on the survival of EPN, their infectivity and their sedimentation speed. The results of the tests for several types of surfactants, humectants and UV-protective adjuvants are presented in this paper. The two best scoring surfactants and the two best scoring humectants were selected for further testing. Subsequently, the effect of the four selected adjuvants (separate and in surfactant-humectant combination) on the deposition of EPN on cabbage and leek leaf discs was tested.