Effects of Pymetrozine on biochemical parameters and the midgut ultrastructure of Anthonomus grandis Boheman (Coleoptera: Curculionidae)

Pymetrozine represents a class of compounds for the control of sucking insects. However, chewing insects have also shown sensitivity to this compound. Therefore, although pymetrozine has been demonstrated to have a direct action on sucking insects, it could also affect species like the boll worm Anthonomus grandis by promoting histological changes in the intestine and alterations in biochemical parameters such as glycogen, lipids, and glucose. The pymetrozine promoted histological changes are characterized by protrusions and detachments of columnar cells toward the intestinal lumen, presence of vacuolated regenerative cells, and removal of the epithelial lamina in some areas of the muscle layer. The ultrastructure of the midgut in the control group exhibited the basal labyrinth near the mid region of the cell, rough endoplasmic reticulum, Golgi complex, glycogen granules, mitochondria, electron-lucent vesicles, nucleus with well-defined nucleoli, and elongated microvillus. Pymetrozine promoted disarrangement in the basal labyrinth and generated numerous vacuoles and large protrusions between the epithelial lamina and muscular layer. No significant difference was observed in glucose content at 48 h after treatment; however, a significant increase was observed at 144 h after treatment. The glycogen content was reduced in the first 48 h of exposure to pmetrozine and reached the average content of the control insects at 144 h. Significant effects were observed in lipid contents, both in the first 48 h and at 144 h after treatment. Thus, we conclude that pymetrozine compromises the digestive physiology in these insects, affects reproduction, and consequently, it can be a potential alternative to reduce this pest species.