Effect of Entomopathogenic Fungi on the Survival, Hemocyte Profile, and Detoxification Enzyme Activity of Yponomeuta padella (L) (Lepidoptera: Yponomeutidae)

Abstract

The small ermine moth Yponomeuta padella (L) (Lepidoptera: Yponomeutidae) is a major pest of certain Rosaceae plants in orchards and forest ecosystems in Iran, causing substantial damage to leaves and young branches. This study evaluates the biology and immune responses of Y. padella under controlled conditions and examines its susceptibility to entomopathogenic fungi (EPF) isolates: Beauveria bassiana (Fashand, 47, b2), Isaria farinosa (1872-c), and Aspergillus sp. (A1). Insects were reared at 24°C ± 1°C, 60% relative humidity, and a 14:10 light–dark cycle. Following hemolymph extraction and Giemsa staining, five hemocyte types were identified using validated morphological keys: prohemocytes, plasmatocytes, granulocytes, oenocytoids, and spherulocytes. Granulocytes and plasmatocytes predominated in the later instars. Bioassays with EPF isolates under the same conditions revealed significant larval mortality. Isolates b2 and 47 induced the highest mortality rates, reaching 70%–75% at the maximum concentration. The most pronounced reduction in pupation and adult emergence rates was associated with isolate b2. The pupal duration increased in all fungal treatments. In contrast, male longevity was reduced across all fungal exposures. Hemocyte counts significantly increased between 3 and 6 h post-treatment, with granulocytes and plasmatocytes peaking. Enzymatic assays demonstrated marked alterations: phenoloxidase (PO) activity peaked at 12–24 h, while glutathione S-transferase (GST) and esterase (EST) activities peaked at 24 and 48 h post-treatment in exposed larvae. acetylcholinesterase (AChE) reduced at 48 h post treatment. These results underscore the biocontrol potential of EPF, particularly B. bassiana, against Y. padella, by significantly affecting developmental dynamics and immune parameters.