Evaluating the potential of <i>Artemisia annua</i> essential oil for controlling <i>Hyphantria cunea</i> (Lepidoptera: Erebidae): effects on larval development, immune function, and enzymatic activities

The fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Erebidae), is a globally pervasive and destructive polyphagous defoliator. This study investigates the effects of Artemisia annua L. essential oil and its two constituents, camphor and 1,8-cineole, on developmental parameters, immune responses, and various enzyme activities in H. cunea larvae. Third instars were topically treated with A. annua essential oil (LD10: 80.74 μg/larva, LD30: 177.08 μg/larva, and LD50: 305.05 μg/larva), camphor (LD10: 98.59 μg/larva, LD30: 246.5 μg/larva, and LD50: 465.03 μg/larva), and 1,8-cineole (LD10: 135.34 μg/larva, LD30: 317.64 μg/larva, and LD50: 573.49 μg/larva). Developmental indices, including larval, pre-pupal, and pupal durations, were extended in treated larvae, while adult lifespan and fecundity were notably reduced in comparison to the control. Exposure to increasing concentrations of A. annua essential oil, camphor, and 1,8-cineole significantly reduced larval hemocyte counts. Granulocytes and plasmatocytes are essential hemocytes responsible for phagocytosis and the encapsulation of harmful agents. A decrease in these cells weakens immune defenses and makes larvae more susceptible to pathogenic challenges. Additionally, the observed decline in both nodulation following Beauveria bassiana injection and phenoloxidase activity underscores an overall suppression of immune function. Antioxidant enzyme activities including superoxide dismutase, catalase, peroxidase, and glucose 6 phosphate dehydrogenase increased significantly in treated larvae relative to controls. Meanwhile, acetylcholinesterase activity declined significantly after 48 h of treatment, and cytochrome P450 monooxygenase levels increased substantially at both 24 and 48 h The findings suggest that A. annua essential oil could serve as a promising, safe, and sustainable option for managing H. cunea.