Pathogen Identification and Treatment of Trichoderma koningiopsis ZL01 Mycosis in Firefly Pygoluciola sp. (Coleoptera: Lampyridae)

The artificial breeding of fireflies is vital for supplementing natural populations. Unfortunately, mycosis is being observed with increasing frequency in the artificial breeding of fireflies, resulting in increased mortality. This study reports the identification of a microfungus that infects larval <i>Pygoluciola</i> sp., a species of semi-aquatic fireflies, during artificial breeding. Morphological and molecular analysis identified the fungi as <i>Trichoderma koningiopsis</i> (named as ZL01 strain). In addition, nystatin was selected out of five candidates as the optimal antifungal agent against <i>T. koningiopsis</i> ZL01, with a minimum inhibitory concentration of 25.00 μg/mL. Acute oral and contact in vivo toxicity tests on larval <i>Pygoluciola</i> sp. confirmed the safety of nystatin. Furthermore, compared to a <i>Pygoluciola</i> sp. larval population infected with <i>T. koningiopsis</i> ZL01, nystatin treatment increased the survival rate of larvae by twofold (spray administration) and threefold (drip administration) at the end of a nine-day artificial breeding experiment. These findings indicate that nystatin could be used as a potential antifungal agent to control mycosis in artificially bred fireflies. This study was the first to document the infection of semi-aquatic fireflies by pathogens and provide a corresponding treatment strategy.