Toxicological impact of herbicides recommended for corn crop in nymphs of Podisus nigrispinus (Hemiptera: Pentatomidae) predator

Abstract

Weeds presence in corn crop (Zea mays L.) may cause high losses in production. Chemical control of these plants is the most used, but may adversely affect natural enemies present in crops. Therefore, the objective of this study was to evaluate herbicides toxicity s registered for corn crop to nymphs of Podisus nigrispinus Dallas, 1851 (Heteroptera: Pentatomidae) predator. It was evaluated the effect of atrazine, nicosulfuron, mesotrione, paraquat and its control based on distilled water over three immature stages of insects (third, fourth and fifth) in doses equivalent to half, to twice, four and ten times the recommended one for corn crop. Herbicides were applied over plastic pots of 500 mL each, containing five nymphs in each stage of the insect, constituting the experimental plot, with six replications. After 96 hours was performed the counting of survivors individuals. For all stages of P. nigrispinus increasing herbicides doses caused a decrease in survival rate. This one was inferior for insects exposed to atrazine and paraquat herbicides. Mesotrione herbicide was the least toxic and nicosulfuron showed median toxicity. It was concluded that nymphs from third to fifth stage of P. nigrispinus natural enemy are more susceptible to atrazine and paraquat herbicides. Moreover, mesotrione and nicosulfuron may be used for controlling weeds in corn crop when the objective is to preserve the population of this predator.