Effectiveness of Aloe (Aloe vera L.) as a protectant of Bacillus thuringiensis var kurstaki against ultraviolet light and biological control agenst of (Spodoptera litura Fab.)

摘要

Spodoptera litura Fab larvae. is a pest that is polyphagic and damaging cultivation plants in the vegetative and generative phases. Control of S. litura larvae can be done with the bacterium Bacillus thuringiensis because its ability to produce protein crystal toxins and cause paralysis in digestive tract of larvae. However, Bt. Is easily degraded in environment by ultra violet (UV) light. This study uses Aloe vera L. extract as Bt. protectant. The method used to test pathogenicity of Btk. bacteria was by using skin extracts and Aloe vera gel exposed to UV light for 3 and 6 hours against second instar of S. litura larvae using 20 larvae and three replications in each treatment. The positive control used was mixture of Btk bacteria with distilled water, whereas the negative control used was only aquades. The results of this study indicate that the mortality rate of larvae in skin extracts and Aloe vera gel exposed to UV for 3 hours and 6 hours was above 50%. In UV irradiation treatment for 3 hours with Aloe vera skin extract, the highest larval death was 72% at concentration of 4.85 × 10~7, whereas in the skin extract and Aloe vera gel, the highest larval death was 75% at concentration of 4.85 × 10~7. In UV irradiation treatment for 6 hours with Aloe vera skin extract, the highest larvae mortality was 68.3% at concentration of 4.85 × 10~7, whereas in skin extracts and Aloe vera gel, the highest larval death was 69% at concentration of 4.85 × 107. It can be concluded that Aloe vera skin extract and gel are more effective as Btk protectants compared to Aloe vera skin extract. Btk. test has sub lethal effects on S. litura larvae, which are smaller size and shape of imago, dead pupae and abnormal imago.