Around them middle of summer, it's a common phenomenon on the golf course to have green footprints appear with brown grass surrounding them.
Creeping bentgrass is a main culprit, but we've seen this issue persist on lawns as well this past summer. A pair of researchers at Iowa State University came up with an hypothesis: DEET (N, N-diethyl-meta-toluamide) mosquito spray. While DEET sprays work great to repel mosquitoes, golf clubs and lawn lovers are finding it deadly to grass!
Undergraduate research associate Zack Olinger, performed a demonstration on this problem for the annual field day in July. This phenomenon occurs when someone stands on the grass and sprays their feet with repellent.
The objectives of this demonstration were to show effects of commercial spray products on the turf and the timeframe for recovery following damage. The team decided to try an aerosol bug spray, a simpler bug spray, and sunscreen.
The goal was to demonstrate the effects of direct application of these products on the turf. Products used were OFF! Deep Woods® (25% DEET), Bug Soother (Lemongrass Oil 0.5%) and Coppertone Sport High Performance® 30 SPF Broad Spectrum (Octisalate 5%, Avobenzone 3%, Homosalate 10%, Octocrylene 10%).
The Results
Off! Deep Woods
The results found that the OFF! Deep Woods Bug Spray caused severe turf damage after application. The turf turned a dark purple (resembling the color of wilted grass) and then started to turn brown within 2-3 hours. By 24 hours after application, the turf is damaged to the full extent. The turf took approximately 3 weeks to return to its original quality. Some spots in the plots never came back and would need to be reseeded or left to fill back in during the cooler weather of fall.
Bug Soother
The Bug Soother showed no adverse effects on the turf. Immediately after application, the turf showed a shiny appearance that wore off after approximately 1 hour. The turf continued to live with no problems throughout the trial.
Coppertone Sunscreen
The sunscreen showed the same signs as the OFF! Deep Woods Bug Spray following application. The turf resembled the appearance of wilt for 3-4 hours and then started to brown out for 2 days until it reached the point of recovery. The sunscreen took approximately 8-10 days to return to its original quality.
Most golfers do not know about this problem, so we're here to spread the word. Reach for a spray with simple ingredients the next time you hit up the course - to ensure the health of the green and the health of the planet.