On the occurrence of Aspergillus flavus Link (Eurotiales: Aspergillaceae) on the Bursa white strain of the silkworm, Bombyx mori L., 1758 (Lepidoptera: Bombycidae) in Türkiye: Isolation, characterization, and pathogenicity

The silkworm, Bombyx mori L., 1758 (Lepidoptera: Bombycidae) has been cultivated in Türkiye for many years as a valuable source of income. However, fungal diseases can have a devastating impact on silkworm farming. In August 2024, numerous hardened, dead silkworm larvae were discovered in a B. mori culture in Istanbul and subsequently taken to a laboratory for examination. Microscopic examination revealed that the source of the infection was a fungus with spherical conidia. DNA was extracted from the cultured fungus, and the ITS gene was amplified and sequenced. According to the sequencing results, the fungus was identified as Aspergillus flavus Link (Eurotiales: Aspergillaceae). Phylogenetic analyses showed that it was closely related to the Chinese isolates. In the bioassay, five doses of A. flavus (1 × 103 to 1 × 107 conidia/mL-1) were sprayed on 30 5th instar B. mori larvae. On the 10th day of application, 100% mortality was observed at the highest dose (1 × 107 conidia/mL-1). The LD50 was calculated to be 3.32 × 103 conidia/mL-1. Aspergillus flavus poses a significant threat to both B. mori and other organisms, as it causes aspergillosis and produces aflatoxin. This study provides the first evidence of A. flavus infection in B. mori in Türkiye, demonstrating that the larvae are highly susceptible to this fungus. The findings highlight the need for continuous monitoring and the implementation of effective antifungal control strategies to protect silkworm health and sustain sericulture productivity.