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Fruit Flies Breeding in House Plants

By Julie Bawden-Davis ; Updated September 21, 2017
Fungus gnats tend to be most active in fall and winter.

The presence of fruit fly-like flies in the indoor garden are often indicative of fungus gnats. Unlike fruit flies, whose larvae feed on decaying fruit, fungus gnat larvae congregate in houseplant soil.

Identification

Fungus gnats (Bradysia) are pests that resemble small mosquitoes, but don't bite. The adults are 1/8-inch-long with spindly legs and antennae. Fungus gnat larvae, which develop in houseplant soil, are white with shiny black heads and are about 1/4-inch long.

Damage

Fungus gnat larvae damage houseplants when they feed on roots and root hairs. According to the Purdue Plant and Pest Diagnostic Laboratory, larvae can also penetrate stems and disrupt nutrient and water uptake, and both adults and larvae transmit disease.

Life Cycle

Fungus gnat larvae generally live and feed in the top 2 to 3 inches of moist soil. Within two to three weeks, they become adult fungus gnats. Female fungus gnats then lay eggs in moist soil and repeat the cycle.

Prevention/Solution

Prevent fungus gnat larvae from living and transforming into adults by letting the top 2 to 3 inches of soil dry. Dry soil also discourages adults from laying more eggs. Adults can be caught on yellow sticky traps known as gnat sticks, and certain insecticides kill adult gnats.

 

About the Author

 

Julie Bawden-Davis is an accomplished writer, who specializes in home and garden. Since 1985, she’s written for a wide variety of publications, including “Organic Gardening,” "Better Homes and Gardens," "Ladies' Home Journal," "Parents," "Family Circle" and "The Los Angeles Times." Her books include "Fairy Gardening" and "Reader's Digest Flower Gardening." Bawden-Davis holds a Bachelor of Arts in journalism and is a certified master gardener.