Effect of chemical treatments on pebrine spore liberation for Tasar mother-moth examination

The Tasar silkworm (Antheraea mylitta) is highly vulnerable to a range of diseases, of which pebrine, virosis, bacteriosis, and muscardine are most common. Among these, pebrine is considered the most destructive, as it alone is responsible for nearly 30-35% of annual cocoon crop losses, and in extreme cases, it can wipe out the entire crop. The disease is primarily transmitted through vertical transmission, wherein the pathogen passes directly from the mother moth to its progeny. Hence, ensuring the production of disease-free layings (DFLs) is of utmost importance in sericulture, which is achieved through systematic microscopic examination of the mother moths. For this purpose, it becomes essential to improve the visibility of pebrine spores under the microscope. This requires the complete liberation of spores from the moth tissues, removal of fat bodies, dissolution of debris, and appropriate staining to provide a clear microscopic field. In the present investigation, several chemical agents were evaluated for their effectiveness in liberating pebrine spores from moth tissues. The results demonstrated that treatments with Sarcosyl, formalin, and ethanol provided superior clarity in the microscopic field, with almost no debris observed. At a concentration of 0.5%, Sarcosyl and ethanol were found to release 212, 000 and 54, 000 more pebrine spores per cm³, respectively, when compared with potassium carbonate (K₂CO₃), which served as the control. At 1% concentration, Sarcosyl treatment liberated 122, 000 additional spores per cm³ over the control. When the concentration was increased to 2%, citric acid, ethanol, and Sarcosyl treatments showed significant improvement, releasing 300, 000, 100, 000, and 500, 000 more spores per cm³, respectively, compared with K₂CO₃. Similarly, at 5% concentration, Sarcosyl, ethanol, and formalin treatments liberated 160, 000, 70, 000, and 100, 000 additional spores per cm³, respectively, over the control. From these findings, it is evident that Sarcosyl, formalin, ethanol, and citric acid were consistently more effective than K₂CO₃ in liberating a higher number of pebrine spores, thereby ensuring improved visibility and reliability in mother moth examinations. Among the tested chemicals, Sarcosyl was the most effective across concentrations, followed by ethanol, formalin, and citric acid. These results highlight the importance of adopting appropriate chemical treatments in mother moth examinations to ensure the production of pebrine-free generations of Tasar silkworms.