Efficacy of entomopathogenic Steinernema and Heterorhabditis nematodes against white grubs (Coleoptera: Scarabaeidae) in peanut fields.

The efficacy of entomopathogenic nematodes (EPNs) against the white grub Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae) in the peanut (Arachis hypogaea L.) fields was evaluated. In the first experiment with a high initial white grub population (24.65 +/- 2.44 larvae per m2) in the field, Steinernema longicaudum X-7 and Heterorhabditis bacteriophora H06 at 10,000 and 5,000 infective juveniles (IJs) per plant contributed to significantly higher percentage reduction of the white grub larvae, lower percentage of the injured legume, and higher peanut yield compared with chlorpyrifos and other treatments. The peanut yields harvested from the plots treated with EPNs at 5,000 IJs per plant were at least 70% higher than that from the untreated control (water) and at least 30% higher than that from chlorpyrifos-treated plots. In the second experiment with a low initial white grub population (8.07 +/- 1.29 larvae per m2) in the field, EPN treatment did not increase peanut yield compared with the other treatments. But both S. longicaudum X-7 and H. bacteriophora H06 gained higher percentage reduction of the white grub larvae and lower percentage of the injured legume than Steinernema carpocapsae (Weiser) All and the control. The cost-benefit of using EPNs for white grub control was estimated to be comparable with that of using chemicals. S. longicaudum X-7 and H. bacteriophora H06 showed promise for white grub control in peanut fields.