Immune and nutritional responses of Podisus nigrispinus (Hemiptera: Pentatomidae) nymphs sprayed with azadirachtin

Abstract

AbstractAzadirachtin is an efficient biopesticide, and it is considered safe for natural enemies because its mode of action is mainly by ingestion. The predator, Podisus nigrispinus Dallas, is found in various agroecosystems as a potential tool for biological control. However, there is much debate on the safety of this stinkbug if azadirachtin is used. Thus, we evaluated the cellular and humoral responses as well as biochemical parameters of the fifth‐instar nymphs of P. nigrispinus treated with azadirachtin. The insects were divided into three treatment groups and sprayed with azadirachtin (Azamax®), deltamethrin (Decis®), and water (control). After 24 h, total and differential hemocyte counts were performed. The analysis of phenoloxidase activity and quantification of nitric oxide, lipids, sugar, glycogen, and protein were performed after an interval of 24 and 72 h. Azadirachtin was found to affect the immune system of this stinkbug and decrease the number of hemocytes, especially pro‐hemocytes and oenocytoids, and it may have caused a reduction in phenoloxidase activity and nitric oxide level. In addition, the decrease in protein levels indicated the interference of azadirachtin in protein synthesis. We conclude that damage caused by the botanical insecticide has been less harmful than that caused by the synthetic insecticide, but use of azadirachtin may still interfere with biological control due to undesirable immune system damage reducing predator efficiency.