The extract of tea leaves (Camellia sinensis (L.) Kuntze) as protectant of Bacillus thuringiensis var. kurstaki against ultraviolet light for control of armyworm (Spodoptera litura Fab.) larvae

摘要

Spodoptera litura is an important insect pest on plants that can reduce crop yields. The bioinsecticides is one of S.litura pest control that save and eco-friendly. Biopesticide can be made from microorganisms like Bacillus thuringiensis which is pathogenic to pests. Production of secondary metabolites by entomopathogenic bacteria can be used as materials for pest control of S.litura. One of the major constraints to use of B.t. for biocontrol of S.litura is its sensitivity to ultraviolet degradation, because spore and crystal of B.t. can be inactive if exposed by UV light. So, this research utilize tea extract as B.t protectan in UV light in laboratory. The purposes of this research were to determine the pathogenesity of B.t. to mortality of S.litura. The method of this research was B.t. suspension added to tea extract and then exposed under UV light for three and six hours. The pathogenesity of B.t. use the third instar larvae S.litura in three replications and control. Controls testred were used B.t. added to aquadest. The mortality data obtained was analyzed statistically by using ANOVA. The analysis showed a significant different in the treatment of UV time exposed and not significantly different in the treatments of concentrations. The pathogencity test showed B.t. killed third instar of S.litura larvae up to 30%-58%. The result of probit analysis LC_(50) dan LC_(90) showed that extract of fresh tea leaves were more pathogenic than extract of packaging tea. Sublethal effect of persistent B.t. to S.litura was the abnormality on pupae and imago. The pupae and imago became smaller than the normal one.