Synergism and unintended effects of the association between imidacloprid and sodium chloride (NaCl) on the management ofEuschistus heros

BACKGROUND The use of insecticidal solutions containing sodium chloride (NaCl) has been proposed as a more environmentally friendly alternative to managing stink bug infestations of Neotropical soybean fields. The potential sublethal and undesirable effects of this practice have, however, been overlooked, especially with novel insecticides. Here, we have evaluated experimentally whether the addition of NaCl (0.5%w/v) to imidacloprid-containing solutions could alter insecticide toxicity and modify the reproductive responses of the Neotropical brown stink bugEuschistus heros. RESULTS Adding NaCl to imidacloprid solutions significantly increased imidacloprid toxicity againstE. heros. The exposure toE. herosto sublethal concentrations of imidacloprid affected the insect's mating abilities in a concentration-dependent manner. The addition of NaCl to solutions containing imidacloprid at concentrations as low as 0.126 mu g a.i. cm(-2)(i.e. the equivalent to 3% of field rate recommendation) also impacted the sexual behavior ofE. heros, reducing mating duration. NaCl-exposed stink bugs, however, exhibited higher fecundity and fertility rates than those insects that were unexposed to NaCl or those that were exposed to sublethal levels of imidacloprid only. CONCLUSIONS The addition of low amounts of NaCl resulted in a higher toxicity of imidacloprid. This practice, however, can also lead to undesirable effects as increasing reproductive output ofE. herosthat can potentially compromise the management of these insect pests.

Automated summary

The addition of NaCl to imidacloprid solutions significantly increased imidacloprid toxicity against E. heros, affecting mating abilities while increasing fecundity and fertility rates. However, this practice may have undesirable effects on insect behavior that could compromise pest management efforts.