Do pesky fungus gnats drive you crazy around your houseplants in your home or office? While these small adult flies are a nuisance, they can harm plants, but not humans. Fungus gnats are problematic where plants are overwatered, especially in peat-based media. Larvae feed on algae, fungi, and plant roots in the growing medium. Usually, non-chemical methods are used to control these gnats on plants growing indoors by watering less frequently, removing algae, or re-potting plants using clean media.
Researchers at University of Illinois and Kansas State University recently evaluated a different approach to repelling adult fungus gnats, using Bounce® original brand fabric softener dryer sheets. The idea for this work came from Master Gardener and trade magazine claims that sheets of Bounce® tucked into pockets of clothing repel mosquitoes. Adult fungus gnats were tested in special containers in the laboratory to determine how many flew into a compartment containing moist growing media or one with moist media and a Bounce® dryer sheet. Results from these experiments showed that 45% of the total number of adult gnats released into the test chamber was collected from the compartment with moistened media, while only 18% were present in the compartment with media and the dryer sheet.
To further investigate the repelling properties of the dryer sheets, volatile compounds were identified. One of the major volatiles detected from the dryer sheets was linalool, which is commonly used in cosmetics and perfumes to produce a floral odor. This compound is also naturally-occurring in plants such as lavender, marjoram, coriander, and basil. In other studies, linalool was toxic to two spotted mites and other insects (sawtoothed grain beetle, German cockroach, Mexican bean weevil, English lesser grain borer, and rice weevil). Also, the citrosa plant (Pelargonium citrosum), which is advertised as a natural mosquito repellant, contains approximately 6.8% linalool.
While researchers demonstrated that Bounce® dryer sheets repel fungus gnats, the period time that dryer sheets are effective as a repellent, the minimum distance required from plants for repellency, as well as the impact of the sheet on egg laying, larva, and plant damage remain unknown. However, this study validates claims that dryer sheets repel fungus gnats and with further development of dryer sheet placement near plants, it may be an alternative strategy to deal with those pesky fungus gnats.
REVISED: December 5, 2011