Larvicidal Efficacy and Histopathological Alterations in the Midgut of Saw-Toothed Grain Beetle Larvae, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), Induced by Melia azedarach Extract and Deltamethrin

Abstract

There were three distinct concentrations of the chemical herbicide that were utilized: 0.2, 1.0, and 0.5 milliliters per liter. An example of a control was water that had been distilled. There was a treatment period of 24, 48, and 72 hours for each dosage. Moreover, the plant extract Melia azedarach was used in three distinct concentrations: two, one, and half a milliliter per liter). For each of the three strengths, distilled water served as the control, and the treatments were carried out for a duration of 24, 48, and 72 hours, respectively. For each treatment, there were three more larval samples that were utilized. Ten larvae were placed in each of the further samples that were taken. Using a dosage of 2 milliliters per liter of the chemical pesticide Deltamethrin, both the insecticide and the plant extract were highly effective in eliminating the bug over a period of 72 hours. After 72 hours, the plant extract performed more effectively when it was at a concentration of 2 milliliters per liter. Due to the environmental hazards of chemical insecticides and the growing interest in Integrated Pest Management (IPM), the histopathological effects of both the synthetic insecticide deltamethrin (2.5%) and the ethanolic extract of Melia azedarach leaves were evaluated against the third-instar larvae of the saw-toothed grain beetle. Histological sections were prepared at a thickness of 4 \mum and stained with hematoxylin and eosin (H&E). Microscopic examination revealed that larvae treatment with the chemical insecticide led to body wall degradation, acute necrosis, and structural disintegration of the midgut wall, along with cellular debris accumulation within its lumen and muscular atrophy. Similarly, the M. azedarach extract induced severe structural destruction characterized by digestive tract deformation, cytoplasmic vacuolation in epithelial cells, and degeneration and rupture of the adjacent Malpighian tubules. These findings demonstrate the high efficacy of both agents in causing a fatal structural and functional collapse of the pest, thereby offering promising prospects for reducing the reliance on synthetic insecticides to ensure environmental safety. The study results confirmed a direct relationship between increased concentration, exposure time, and mortality rate, and that O. surinamensis larvae were more sensitive to all the treatments under study.