The Fungus Gnat Test
In 2011, researchers at the University of Illinois and Kansas State University tested whether Bounce fabric softener dryer sheets (made by Procter & Gamble) can repel fungus gnats. According to the research:
The idea came from Master Gardener and trade magazine claims that “sheets of Bounce tucked into pockets of clothing repel mosquitoes.“A test chamber was set up in a lab. The chamber included two compartments; one with a moist growing media and one with moist media and a Bounce dryer sheet.Adult fungus gnats were released into the chamber.The test was to see how many of the gnats flew into each compartment.The results: When the test was concluded, 45 percent of the adult gnats released into the test chamber were collected out of the compartment with moistened media; only 18 percent were present in the compartment with media and the dryer sheet.
From these results, the testers took it a step further to determine just what was in the dryer sheets that could cause the insects to be repelled. They identified linalool, a volatile compound, as a major compound in the sheets.
Linalool as Repellant
Linalool is a common floral-scented ingredient used in cosmetics and perfumes. It also occurs naturally in some plants, including lavender, marjoram, coriander, and basil. According to the Fungus Gnat investigation, studies have found that linalool does indeed have repellent effects on some insects, including spotted mites, sawtoothed grain beetle, German cockroach, Mexican bean weevil, English lesser grain borer, and rice weevil. Linalool is used in some mosquito repellent sprays. However, a 2007 EPA review of linalool states, “A preliminary screen of labels for products containing Linalool (as the sole active ingredient) indicates that efficacy data on file with the Agency may not support certain claims to repel mosquitoes.” A study reported in 2009 by the National Center for Biotechnology Information (NCBI) found that linalool was more effective as a mosquito repellent than citronella but less effective than geraniol.
Keep Deer Away
You may also see dryer sheets hanging on stakes around gardens to repel deer. While these may indeed work, it is probably because the dryer sheets have been sprayed with a repellent, as advised by the Rhode Island Department of Environmental Management, Division of Fish and Wildlife. The department also notes that deer can be repelled by:
Soap sachet: Place a bar of soap made with tallow fatty acid in a nylon sock or cheesecloth, and hang from targeted bushes and shrubs.Hair sachet: Place unwashed cut hair (from a local barber) in a nylon sock or cheesecloth, and hang from bushes, trees, etc.
