Biology of <i>Stiphrometasia monialis</i> (Erschoff) (Lepidoptera: Crambidae) and its immune response against the entomopathogenic fungi

Abstract Stiphrometasia monialis (Erschoff) (Lepidoptera: Crambidae) is a significant pest of Capparis spinosa in Iran in recent years and it causes great damage to the fruits of this medicinal plant. This study investigates the developmental and immune responses of Stiphrometasia monialis under controlled conditions and assesses its susceptibility to entomopathogenic fungi (EPF) isolates of Beauveria bassiana (566, b2, N1), Metarhizium anisopliae (Ir‐M‐22), and Isaria farinosa (1872‐c). Larvae, reared at 25 ± 1°C, 50% humidity, and a 14:10 light–dark ratio, undergo five instars, reaching 19.0 mm in length in the fifth instar. Eggs, approximately 0.5 mm in diameter, are laid singly on caper buds and fruits. The average incubation period for S. monialis eggs is 6.3 days. Five haemocyte types—prohaemocytes, plasmatocytes, granulocytes, oenocytoids and spherulocytes—were identified, with granulocytes being most prevalent in later instars. Bioassays with EPF isolates under these conditions showed significant larval mortality. The isolate b2 achieved the highest mortality rate of 78.5% at the highest concentration. b2 treatment also notably reduced pupation and longevity, impacting fecundity. Haemocyte counts increased significantly within 3–6 h post‐treatment, with peaks in granulocytes and plasmatocytes. Enzyme activity assays revealed significant changes: phenoloxidase (PO) and glutathione S‐transferase (GST) peaked at 6 h, acetylcholinesterase (AchE) activity was reached to peak at 12 and 24 h in treated larvae. Esterase (EST) activity elevated sharply at 6 and 12 h post‐exposure. These findings highlight the potential of EPF, particularly isolate b2, for effective biocontrol of S . monialis , demonstrating substantial impacts on developmental stages and immune responses.