Efficacy of Bacillus thuringiensis subsp. aizawai against the Greater Wax Moth, Galleria mellonella (Lepidoptera: Pyralidae) in Libya: A Bioassay Approach for Sustainable Wax Moth Control

Abstract

The greater wax moth belongs to the order Lepidoptera, family Wax Moth. It is a serious and destructive pest in honeybee farming, causing significant losses to honeycomb throughout North Africa. Due to its severity, most beekeepers in the region resort to dangerous chemical pesticides such as paradichlorobenzene (Paradex), leading to its accumulation in bee products and posing an environmental risk. This study aims to evaluate the effectiveness of a microbial pesticide (Bacillus thuringiensis genus aizawai) on the larvae and its mechanism of action in controlling them. The larval stages of the greater wax moth were obtained from infested bee colonies and reared in a nutrient-rich medium. Tests were conducted at different concentrations of the microbial pesticide: 1.0%, 1.8%, 3.3%, and 6.0%. The results of a one-way ANOVA analysis showed a dose-dependent difference in larval mortality. At a concentration of 6.0%, larval mortality was 100%. The mean standard deviations clearly and statistically significant (p < 0.05) confirm the effectiveness of the higher concentrations (6% and 3.3%) of the pesticide, indicating the efficacy of its active ingredient, B. thuringiensis. The alkaline environment within the midgut causes the bacteria's toxic crystals to rupture the tissue and lyse the epithelial cells, leading to septicemia and larval death. (Midgut of the larva.) Spraying stored wax combs with a 3.3% microbial pesticide in the fall protects the combs from infestation by this pest, thus contributing to reducing or avoiding chemical control, which ensures that honeybee products meet health standards and are exported abroad.