Turf Trouble: Does The DEET In Bug Repellent Really Kill Grass? Year II

Overview

There is anecdotal evidence that suggests bug sprays containing DEET damage grass, but there are no rigorous peer -reviewed studies on the topic. DEET, or N,N -diethyl-meta-toluamide, is a neurotoxin that affects the olfactory receptors in insects and verteb rates, inhibiting their ability to locate humans and causes transient neurotoxic effects in insects. However, there are no published studies on DEET’s effect on plants. In Year I of this study, we demonstrated that bug sprays containing DEET kill grass. Th is year, we created our own solutions with different concentrations of DEET with 60% ethyl alcohol to identify what chemical compound within the bug spray was damaging the grass. To standardize our treatment and planting procedure, we created 3D -printed to ols using Solidworks and developed quantitative methods to analyze changes in grass color. Direct spraying of solutions containing DEET killed grass in a dose - dependent manner in both a controlled, indoor environment and on three different species of grass in an outdoor environment. Grass that died due to DEET exposure did not recover even up to 30 days after exposure. The application of DEET to the soil damaged nearby grass and was almost identical to damage from direct application. Furthermore, an untarge ted metabolomics analysis of treated grass revealed significant differences in metabolomes of treated grass within 1 hour of DEET application, indicating a rapid toxic mechanism. Our results are the first rigorous demonstration that it is the DEET in bug spray, not the ethanol, that kills grass.