Synergistic effect of entomopathogenic nematodes and thiamethoxam in controlling Bradysia odoriphaga Yang and Zhang (Diptera: Sciaridae)

Abstract Six entomopathogenic nematode species (EPNs) ( Heterorhabditis bacteriophora H06 (H06), Steinernema carpocapsae NC116 (NC116), Steinernema carpocapsae All (All), Steinernema longicaudum X-7 (X-7), Steinernema feltiae SF-SN (Sf) and Heterorhabditis indica LN 2 (LN 2 ) were tested for virulence against 3rd instar Bradysia odoriphaga , and their interactions with thiamethoxam against 3rd instar B. odoriphaga under laboratory and greenhouse conditions were also evaluated. S. feltiae SF-SN, which is the most virulent, was selected to evaluate the synergism effects with thiamethoxam at different concentrations under laboratory conditions. S. feltiae SF-SN and thiamethoxam were either applied alone or in combination, and the combined application manner was evaluated in the greenhouse. Under laboratory conditions, a synergistic effect was found between six EPNs and thiamethoxam. The combination effects of Sf, All and LN 2 species caused significantly higher mortality than the other three treatments (X-7, H06 and NC116). Furthermore, the combination of Sf and All species led to a significantly higher control effect than LN 2 in greenhouse tests. In further greenhouse tests, the combination effect of Sf (0.75 billion IJs/ha) + thiamethoxam (1.0 kg a.i./ha) applied twice (28 day intervals) was significantly higher than a single treatment of Sf + thiamethoxam at twice the dosage. Compared to the single thiamethoxam application, the combination effects of Sf and thiamethoxam had the highest value at over 90% of the control effects for up to 6 weeks. Therefore, the integrated technique of the synergism of S. feltiae SF-SN species and thiamethoxam to control B. odoriphaga could be useful for integrated pest management in the future.