Studies On Application Of Entomopathogenic Nematodes For The Control Of Bradysia Odoriphaga

Entomopathogenic nematodes (EPNs) have good application prospects for the control ofchive midge, Bradysia odoriphaga Yang et Zhang (Diptera: Sciaridae). In the present study,effects of strain and application rate on EPN infectivity to the chive midge were evaluated andthe field trials of using the selected EPN isolates for the control of the chive midge were alsocarried out. The synergistic interaction between environment-friendly chemicals(chlorantraniliprole, diflubenzuron, imidacloprid, and toosendainin) and EPN for chive midgecontrol were tested. The safety of the chemical insecticides, which were commonly used incontroling the chive midge, to the EPN was also evaluated. These studies provide referencesfor the large-scale application of EPN to control the chive midge in field.The commercialized productions of EPN, Heterorhabditis bacteriophora H06and H.indica LN2performed better than Steinernema longicaudum X-7and S. carpocapsae All,which showed higher infectivity to the chive midge at25-30°C. Heterorhabditis indica LN2was superior to H. bacteriophora H06with80%infectivity at the concentration of75IJs/larva. In the field trials,14d after application, the larva population in the field treated withH. indica LN2at the concentrationof22.5×108IJs ha-1decreased to just half as before, whichhas no significant difference to that with phoxim. In the late period (35-77d), there was anoutbreak of chive midge in the field treated with phoxim, with larva population went up to1195larvae/m2. While in the fields with EPN treatment, much lower larval population (<100larvae/m2) was recorded, which indicated good persistence of the EPN.No negative effect of the environment-friendly chemicals, chlorantraniliprole,diflubenzuron, imidacloprid and toosendainin were found on the survival and infectivity of H.bacteriophora H06and H. indica. Only imidacloprid showed synergistic interaction with H.bacteriophora H06and H. indica LN2for chive midge. When comparing with applying thenematodes alone, with infectivity of <37.5%imidacloprid could improved the infectivity ofthe nematodes to77.5-97.5%when using them together.Among the tested eight chemical insecticides that were commonly used in the productionof China chive, beta-cypermethrin, triadimefon, dimetachlone and carbendazol had no effecton the survival and infectivity of H. bacteriophora H06and H. indica LN2, they could beapplied normally before EPN application. Dichlorvos caused high mortality of the nematodesand could not apply together with the nematodes. Phoxim, chlorpyrifos and emamectinbenzoate had no effect on the survival of H. bacteriophora H06but did affect the survival ofH. indica LN2, although they all had no effect on the infectivity of the two nematodes. Both nematodes could be released10,10,20days after the application of phoxim, chlorpyrifos andemamectin benzoate, respectively.A comparision of cost for using H. indica LN2and phoxim for the control of the chivemidge was made. The data indicated that the cost for using H. indica LN2was450RMBmore than that using phoxim per hactre. But good persisitance of nematodes can obtainsustainable control and result in good quality of the chives which are without pesticides’residual. Our result proved that EPNs has the potential to replace chemical pesticedes for thechive midge control in China chive production.