Laboratory evaluation of the effect of Beauveria bassiana on the vital activity of Grapholitha molesta (Lepidoptera : Tortricidae)

Abstract

Improving yield and quality of the economic crops is a central task in agriculture. One of the great potentials of agriculture is to protect crops from pests. Chemical pesticides have widely used in agricultural production, but excessive amount of them has resulted in many environmental and pest-resistance problems. With the increasing demand for organic products, biopesticides have been an alternative to conventional chemical ones. Moreover, biopesticides are more and more favored by the pesticide market because of their safety for environment, and their unique mechanism of action which is not easy to produce resistance. Entomopathogenic fungi have a wide host range, and they are environment friendly and can markedly improve pest control efficacasy. Entomopathogenic fungi can also as biological control agent against the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a significant pest of stone and pome fruits. Beauveria bassiana is one of the most widely studied entomopathogenic fungus and it is used as biopesticide. B. bassiana, is a broad spectrum entomopathogenic fungus with strong pathogenicity. It is easy cultured and its pathogenic is enough to keep pest populations below an economic threshold level. It has a special status in field of biological control. In order to better understand its mechanism and control effect on oriental fruit moth, in this study we analyzed the lethal effect under two different infection modes of B. bassiana and the affection of three concentrations of spore suspensions. The fourth instar larvae of oriental fruit moth were treated by impregnation method and the feeding method at different spore suspension of 1×105 conidia/ mL, 1×106 conidia/mL, 1×107 conidia/mL, the mortality rate and body weight were calculated. The results showed that the maximum corrected mortality rate of cuticular infection and digestive tract infection on oriental fruit moth infected by B. bassiana was 65.7% and 22.7%, respectively. Compared with the control group, the body weight was decreased in different degrees. Under laboratory conditions, the concentration of B. bassiana of 1×107 conidia/mL is the economical and effective concentration for the control of the oriental fruit moth.