The biocontrol activity of both Bacillus thuringiensis and Beauveria bassiana against Spodoptera litura and their toxic effect on the insect metamorphosis
摘要
Armyworm, Spodoptera litura (Lepidoptera: Noctuidae) is a very devastating insect pest that causes severe economic losses to a wide range of crops. S. litura attacks various host plants including vegetables, crops, fruits, and ornamentals. Various entomopathogens that infect insects including wide species of bacteria and fungi are effective biocontrol agents against lepidopterous pests. The effectiveness of two entomopathogens, Bacillus thuringiensis (Bt) and Beauveria bassiana (Bb) was evaluated in this study against S. litura under controlled conditions. The larval length was lower when Bb107 (0.87 cm for 3rd and 1.33 cm for 4th instar) and Bt107 (1.03 cm for 3rd and 1.93 cm for 4th instar) were applied in comparison to the control (2.70 cm for 3rd and 3.40 cm for 4th instar). Similar results were recorded for larval weight, which was reduced by using higher concentrations of Bb107 and Bt107. The larval duration was increased after the application of Bb107 (7.77 d) in comparison to the control (4.01 d). Similar effects of higher concentrations of both entomopathogens were recorded on pupae. The larval mortality was higher when Bb107 (55.3%) and Bt107 (61.1%) were applied. A lower number of pupae were converted into adults, by using Bb107 (20.1%) and Bt107 (10.3%) as compared to the control (92.3%). These findings indicate that higher concentrations of both EPs possess the potential to effectively manage the destructive insect pest S. litura. Moreover, the negative effect was achieved on the live larvae till they reached the adult stage. Taken together, our results suggest that higher concentrations of both EPs are a potential biocontrol agent against S. litura and can be used as a substation for chemical insecticides, which cause many serious problems for plant health and the environment.