Effect of sublethal concentrations of insecticides associated with NaCl and KCl on feeding behavior and mortality of Euschistus heros and Diceraeus melacanthus (Hemiptera: Pentatomidae)

Abstract

Stink bugs are important pests of highly profitable agricultural crops worldwide, and the use of insecticides remains the main strategy for their control. The objectives of this study were to evaluate the behavioral aspects of Euschistus heros and Diceraeus melacanthus through feeding after exposure to chloride solutions (NaCl and KCl), as well as the control efficacy of insecticides in combination with salt. Two bioassays were performed with stink bugs exposed to treated substrate: i) feeding preference by salivary sheath counting in a free choice test for chloride solutions, using bean pod or corn seedling as counting substrate for newly emerged E. heros and D. melacanthus adults, respectively; and ii) comparative efficiency of five synthetic insecticides associated with NaCl or KCl in the mortality of 4th instar nymphs (N4). Pre-determined sublethal (LC25) and median lethal (LC50) concentrations of commercially available insecticides (Lfn), buprofezin (Bpf), pyriproxyfen (Ppx), chlorantraniliprole (Ctn) and spinosad (Spn) were used. For each species and insecticide, the treatments were pure LC25, LC25 + NaCl 5% m/m, LC25 + KCl 5% m/m, pure LC50, and distilled water (dH2O) as the control. Corn seedlings treated with 5% NaCl saline solution had reduced salivary sheaths from D. melacanthus. Ctn LC25 (0.63 mL L-1) + 5% NaCl and pure Ctn LC50 (1.16 mL L-1) were similar and more efficient in terms of mortality of D. melacanthus N4s than any other treatment. The association of Spn LC25 (0.37 mL L-1) + 5% NaCl and Spn LC50 only (0.90 mL L-1) was similar to that of E. heros N4s compared to other treatments. The insecticide concentrations used in this study have potential for stink bug pest control, thus the association of insecticides with commercially available, easy-to-find, and low-cost chloride salts may represent a good strategy for stink bug control.