Entomopathogenic nematodes as biocontrol agents tomato leafminer Tuta absolute compared with the chemical insecticide, Emamectin benzoate.

Abstract

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is an invasive alien species especially infested tomato crops. It invaded Egypt in 2009 and many plantations. It's difficult to control due to the limitation of insecticides, therefore, the susceptibility of T. absoluta to three indigenous isolates of entomopathogenic nematodes in Egypt, i. e. Heterorhabditis bacteriophora (EKB20), Steinernema sp. (B32) and Heterorhabiditis sp. (Kasassien isolate) were determined in the laboratory, greenhouse, and field experimental compared with emamectin benzoate insecticide. Leaf bioassays were carried out to evaluate the affinity of nematode isolates to reach the larvae and affect them at the galleries. The efficacy of the three nematode species after foliar application to potted tomato plants was evaluated under laboratory conditions. High larval mortality (70.6-94%) and low pupae mortality (<25%) were determined. In the leaf bioassay tests, a high level of larval infestation (75.4-88.6%) indicated the nematode's ability to kill the larvae within the galleries compared with 100% mortality of emamectin benzoate with the recommended dose. In the pot experiments treatment plants with nematode caused a reduction in insect infestation by 87-94% compared with 96% in the treatment of emamectin benzoate. The results of the field experiment showed the efficiency of entomopathogenic nematodes for reducing infestation with T. absoluta with 70 to 90 % reduction % compared with more than 95% with emamectin benzoate. The results suggested that EPN are considered promising biocontrol agents, if correctly applied and released in integrated control schemes against the tomato leaf miners T. absoluta.