Toxicity and cytotoxicity of the insecticide imidacloprid in the midgut of the predatory bug, Podisus nigrispinus

The selectivity of insecticides on natural enemies in pest control are an important strategy for Integrated Pest Management. However, insecticides can have side effects on non-target organisms such as natural enemies. This study evaluated the histological and cytological changes mediated by the sublethal concentration of the imidacloprid insecticide on the midgut of non-target predator Podisus nigrispinus (Heteroptera: Pentatomidae), used in the biological control of pests. Imidacloprid was toxic for P. nigrispinus with LC₅₀ = 3.75 mg L^-1 and survival of 51.8%. This sublethal concentration of imidacloprid causes histological alterations in the midgut epithelium and cytotoxic features were irregular border epithelium, cytoplasmic vacuolation, and apocrine secretions in the first 6 h after exposure with the insecticide. Apoptosis in the digestive cells occurs after 12 h of exposure in the midgut. These results suggest that imidacloprid may affect the digestive physiology of P. nigrispinus and compromise the effective predation of this insect a biological control agent. The associated use of this insecticide with the predator in pest control should be carefully evaluated.

Permethrin induces histological and cytological changes in the midgut of the predatory bug, Podisus nigrispinus

Insecticides used in the agriculture and forestry have side effects on non-target organisms used as natural enemies. This study evaluated the histopathology and cytotoxicity of permethrin on the midgut of the non-target predatory bug, Podisus nigrispinus (Heteroptera: Pentatomidae) used in the biological control of pest insects. The toxicity and survival of this insect were determined using six concentrations of permethrin via ingestion. Histological and ultraestutural changes of the midgut of P. nigrispinus were analyzed after exposure to permethrin. The insecticide caused toxicity in P. nigrispinus with LC₅₀ = 0.46 μg L^-1 and survival of 47% after 72 h of exposure. The histological changes in the midgut were irregularly bordered epithelium, cytoplasmic vacuolization and apocrine secretions in the lumen after 6 h following exposure to the insecticide. Cytotoxic effects such as granules and vacuoles secreted into the lumen, presence of autophagosomes, and dilatation of infolds of the basal plasma membrane were observed in the three regions of the midgut. Cells of the midgut in apoptosis occurred after 12 h of exposure. Permethrin causes toxic effects, inhibits survival, and produces changes in the histology and cytology of the midgut in P. nigrispinus, suggesting that the cell stress induced by this insecticide can disrupt physiological processes such as digestion, compromising the potential of the predator as a biological control agent of pests. The low selectivity of permethrin to a non-target organism such as the predatory bug, P. nigrispinus indicates that the associated use of this insecticide in biological control should be better evaluated.