Entomopathogenic nematodes (EPNs) are an important component of integrated pest management (IPM) strategies; understanding their compatibility with other biocontrol options is of crucial importance in promoting their use. In this study, the toxicity of azadirachtin, sulfoxaflor, spindle oil (Mineral oil), and thyme oil was tested on the survival and pathogenicity of Steinernema carpocapsae (Weiser, 1955) (Rhabditida: Steinernematidae), Steinernema bicornutum sp. n. (Rhabditida: Steinernematidae), Heterorhabditis bacteriophora (Poinar, 1976) (Rhabditida: Heterorhabditidae), and Heterorhabditis indica (Poinar, Karunakar & David, 1992) under controlled conditions (25 ± 1 °C, 60 ± 10% RH). The toxicity of aforementioned agrochemicals to EPNs was evaluated in 12-well plates and the infective juveniles (IJs) of each EPN species (6000 IJs/50 µL ddh2O) were exposed to the recommended field concentrations of agrochemicals. In the pathogenicity tests, the agrochemical and IJs solutions (3000 IJs/ml agrochemical) were applied to potato tubers in plastic containers which contained 20 adults of Planococcus citri (Risso, 1813) (Hemiptera: Pseudococcidae). The survival of IJs and P. citri (Adults) was evaluated daily for three consecutive days after treatment. The results revealed that all tested EPN species were quite compatible with tested agrochemicals and showed survival of over 95% after 72 h of exposure to tested agrochemicals. EPNs and spindle oil combination induced the highest mortality of adult P. citri, and all EPN species caused mortalities over 90% at 72 h after treatment, except for S. bicornotum-spindle oil combination. Additive effects were observed in all combinations of EPNs with agrochemicals except for thyme oil. It appears, therefore, that EPNs applied in combination with azadirachtin, sulfoxaflor, and spindle oil have a great potential for successful control of P. citri. However, further studies are still required to determine the antagonistic or otherwise synergistic effects of tested chemicals on EPNs in controlling P. citri under field conditions.
