Pathogenicity of nuclear polyhedrosis virus to Galleria mellonella L. (Lepidoptera: Pyralidae) and its control on stored beeswax foundations

Abstract

A nuclear polyhedrosis virus (GmMNPV) was isolated from the greater wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae) larvae from a dead laboratory colony. A semi-synthetic diet was used for rearing G. mellonella at room conditions of 25–30 °C and 60–70% relative humidity. The polyhedral inclusion bodies (PIBs) of the virus were extracted and bio-assayed versus larvae of L3 of G. mellonella in 5 concentrations, i.e., 2 × 102, 2 × 103, 2 × 105, 2 × 107, and 2 × 108 PIBs/ml mixed in the diet (1 ml:1 g). Histopathological study was carried out through a light microscopy of 6–8 μm cross sections in larvae fed on diet contaminated with the virus (2 × 108 PIBs/ml in 1 g diet). The virus infected the nuclei in all organ cells of both ectodermal origins, e.g., hypoderm, tracheal epithelial cells, cells of salivary glands, epithelial cells of fore- and hindgut, and those of mesodermal origin, e.g., fat bodies and cortex of ganglia of the nervous system. Experimental protection of artificially infested beeswax foundations by spraying (2 × 107 PIBs/ml) kept the wax foundations weight loss at 0.4% for 4 months storing, while those artificially infested without virus treatment were completely devoured (100%) by larvae of the pest within 4 months due to successive pest generations. This treatment is recommended for protecting the stored beeswax foundations and combs as a safe alternative to the traditional hazardous chemical insecticides.