Sodium chloride: an insecticide enhancer for controlling pentatomids on soybeans

Abstract

Field and greenhouse studies were conducted during 1990-1995, to determine the effect of the addition of sodium chloride (NaCl) to insecticides, on the control of pentatomid stink bugs (Nezara viridula L., Piezodorus guildinii (West.) and Euschistus heros (Fab.)) feeding on soybeans (Glycine max Merrill). Screening tests were developed applying several chemical insecticides, with and without addition of sodium chloride at 0.5% in water. Insect population was evaluated by the ground cloth sampling method, on several dates after insecticide application. For studying the hypothesis of sodium chloride attractiveness to stink bugs, large soybean fields were split into ca. 1 ha plots, where insecticides with and without salt addition were applied. Stink bug preference for soybean plants sprayed with NaCl solution or distilled water was tested on small cages inside greenhouse, and in small field plots, where several concentrations of NaCl were applied. Results showed that NaCl did not attract stink bugs, but had an arresting effect over the bugs, which preferred salt-sprayed plants, compared to plants receiving distilled water. Addition of NaCl to monocrotophos and metamidophos increased stink bug mortality by insecticides, allowing a reduction of at least 50% of the recommended rate, without reducing the residual effectiveness.