Effective Control of Tuta absoluta (Meyrick) Using Solubilized Endotoxin Proteins From Bacillus thuringiensis

Abstract

Tuta absoluta is a pest that causes serious damage to tomato crops worldwide. It has been known to be difficult to control because it burrows into the crop and causes damage. Even with the representative microbial insecticide, Bacillus thuringiensis of which insecticidal endotoxin proteins are present in the form of large crystals, which prevents them from penetrating the crop where the T. absoluta larvae are located. Therefore, the control efficacy of B. thuringiensis against T. absoluta in cultivation fields has been reported to be low. In this study, we attempted to effectively control T. absoluta larvae in tomato crops by using solubilized endotoxin proteins rather than crystals. The solubilized endotoxin proteins exhibited insecticidal activity 1.4–2.7 times higher than that of crystalline endotoxin proteins. Moreover, the insecticidal effect was over 90% when applied together with Silwet L-77, a surfactant that facilitates the efficient diffusion and penetration of the endotoxin proteins applied to tomato crops. The solubilized endotoxin proteins combined with Silwet L-77 could effectively control T. absoluta larvae in tomato crops severely infested with the corresponding pest. These results suggest a novel control strategy that could be useful for controlling leaf-miner pests such as T. absoluta using B. thuringiensis.