Application of Entomopathogenic Nematodes to Control Larvae of Temnorhynchus baal (Reiche and Saulcy) Under Laboratory Conditions and In Strawberry Fields

Abstract

The white grub, Temnorhynchus baal, is a major pest of the strawberry crop in many Asian and African countries. The white grabs cause significant economic losses in the yield. The present study aims to evaluate the effectiveness of entomopathogenic nematodes (EPNs) on the third larval instar of T. baal under laboratory conditions. The study extended to compare the efficacy of a combination of EPNs ( Steinernema glaseri + Heterorhabditis bacteriophora ) against a natural infestation of T. baal with an organophosphorus insecticide (Diazinon) in an Egyptian strawberry field. In the laboratory, five larvae of T. baal were placed in soil and infected with EPNs. At the highest concentration of 4000 IJs/larva, the larvae were more susceptible to infection with S. glaseri than H. bacteriophora , with mortality percentages of 96 and 88%, respectively. The LC50 of S. glaseri and H. bacteriophora was 937.44 and 1026.58 IJs/larvae, respectively. The mortality percentage was 96% and 100% when treated for five larvae/cup and one larva/cup, respectively, after being infected with a combination of S. glaseri + H. bacteriophora . The mortality percentage was higher in the mixture than for each species studied individually. In the field, throughout the seasons, the percentage of wilted plants was 17.64, 66.09, and 83.95% in 2020 and 12.56, 67.87, and 75.62% in 2021, for the plots treated with a combination of EPNs, insecticides, and control, respectively. Present findings indicate that entomopathogenic nematodes are good alternatives to control the white grub, T. baal , in strawberry fields.