Resposta imunológica e nutricional do predador Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) tratados com bioinseticidas e sua associação a patógenos

Abstract

Biological control uses natural enemies to regulate populations of pests below their level of economic damage. While botanical insecticides such as azadirachtin, although considered safe, are showing to be harmful to natural enemies. However, for effective pest management, the control methods used should act synergistically or without negative interaction. In this study, we evaluated the immune and nutritional response of Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) nymphs sprayed with azadirachtin (Azamax®) after 24h and 72h of treatment, by counting hemocytes, nitric oxide quantification, phenoloxidase activity , quantification of lipids, sugars, glycogen and total proteins. Therefore, the reduction of pro-hemocytes and oenocytes was observed, with consequent reduction of phenoloxidase activity as well as reduction of nitric oxide and protein levels, indicating interference in protein synthesis. When we observed these results, we then analyzed the toxicity of azadirachtin associated with Metarhizium (Metarril®) and Bacillus (Xentari®) pathogens compared to the synthetic insecticide deltamethrin (Decis®), performing the analysis of survival of nymphs sprayed and fed with treated prey with the compounds in the laboratory, and mortality rate after plants treated with the compounds. Only in the treatment of azadirachtin with Metarhizium in greenhouse was observed an increase in predator mortality. Thus, azadirachtin does not show an acute effect on P. nigrispinus, but it may impair its immune system making it more susceptible to fungus infection, requiring management maneuvers that reduce the susceptibility of this insect in the field.