Efficiency of insecticides on nymphs and adults of Dichelops melacanthus(Dallas, 1851) (Hemiptera: Pentatomidae)

Abstract

Thegreen-belly stink bug, Dichelops melacanthus, stands out as one of the main pests of the corn crop, mainly for its potential damage at the beginning of crop development, due to the sap suction at the base of seedlings, causing tillering and trimming symptoms, decreasing productivity and product quality. Aiming at the control of thestink bug, the objective of the present research was to evaluate the effect of insecticides, as well as the lethal time(LT50) of these products on D. melacanthus. To perform the tests, it was used third instar nymphs and adults of D. melacanthusaged up to 72 hours, which were individualized in Petri dishes. For the application of the insecticide, corn leaves were collected and placed in plastic trays. With the aid of a pressurized spray, the insecticides Acefathe + Aluminum silicate (5 g/L), Thiamethoxam + Lambda-Cyhalothrin (1 mL/L), Imidacloprid + Bifenthrin (1.75 mL/L), Bifenthrin + Zeta-Cypermethrin (0.75 mL/L) and Azadiractin (10 mL/L) were applied. In the control, only distilled water was applied. Subsequently, the pulverized leaf pieces were individualized in the Petri dishes, where the third instar and adult bedbugs were already allocated. After application, each treatment was evaluated at 15, 30 minutes, 1, 3, 5, 24 and 48 hours, accounting for insect mortality. Tocorrect mortality, the values were transformed using the Scheneider-Orelli formula. The relationship between the periods of action of the insecticides on the mortality rate of insects was verified by nonlinear regression analysis, using the mathematical model of dose-response. All chemical insecticides evaluated were effective in controlling third instar nymphs; however, when applied to adults, Thiamethoxam + Lambda -Cyhalothrin and Acefathe + Aluminum silicate had reductions in bedbug mortality. Azadiractin showed low efficiency in controlling nymphs and adults of D. melacanthus. Insecticides showed better LT50 in nymphs when compared to adults. The insecticides Imidacloprid + Bifenthrin, Thiamethoxam + Lambda -Cyhalothrin and Bifenthrin + Zeta-Cypermethrin obtained the best LT50 responses for nymphs and adults of the green-belly stink bug. All chemical insecticides evaluated can be used in the integrated management of D. melacanthus.