Guanfeng Liu, Tong Jiang, Rui Wu, Sheng‐Yen Wu
BACKGROUND: The striped flea beetle, Phyllotreta striolata, is a destructive pest of Brassicaceous vegetables, and its management still relies largely on chemical insecticides. The development of environmentally compatible control strategies that provide reliable field performance across pest life stages is therefore a priority. Entomopathogenic nematodes (EPNs) represent a promising alternative, but their field efficacy depends strongly on formulation, application rate, and compatibility with other biological control agents. RESULTS: achieved control efficacy comparable to a higher rate. Compatibility assays revealed that enhanced control was combination-specific and occurred only when EPNs were applied together with Beauveria bassiana, whereas combinations with Metarhizium anisopliae or Bacillus thuringiensis did not provide comparable improvement. Field validation further confirmed that the optimized EPN-B. bassiana treatment achieved pest suppression similar to that of a conventional chemical insecticide. CONCLUSIONS: An optimized combination of S. carpocapsae and B. bassiana provides effective field control of P. striolata by exerting complementary effects on soil-dwelling larvae and foliar-feeding adults. This study demonstrates that careful optimization of formulation, application rate, and agent compatibility is essential for achieving stable biological control under field conditions, supporting the integration of EPN-fungus strategies into practical pest management programs. © 2026 Society of Chemical Industry.