Fruit Flies & Greenhouses

Identifying Fruit Flies

• Fruit flies are similar to gnats in appearance. They have wings and red-colored eyes. Fruit fly bodies are only one-eighth of an inch long, thus making it uncomplicated to enter a greenhouse through tiny holes in window screens and gaps in doors. The front section of the fruit fly's body is tan and the rear section is black. Fruit flies lay their eggs on moist, organic matter or the surface of rotting or fermenting foods.

Chemical Control

• Using pesticides is an effective way to get rid of fruit flies. Azadirachtin and pyrethrins plus piperonyl butoxide insecticidal sprays are effective in eliminating the fruit flies and safe for use in greenhouse. Spray the insecticide in spots where the pests are most prevalent to prevent destroying natural enemies as well.

Non-Chemical Control

• Make non-toxic traps for the fruit flies by opening a packet of activated dry yeast and pouring it into a jar. Measure one-third of a cup of warm water and add it to the yeast. Do not use boiling or hot water. Stir the liquid to help the yeast to dissolve. Cover the jar opening with a clear sandwich bag and secure it with a rubber band around the rim of the jar. Place your finger on the sandwich bag and press down to make it go inside the jar. Poke a tiny hole in the plastic with a toothpick. The fermenting yeast odor attracts the fruit flies into the bag and they can't escape. Empty the jar outdoors after a week, clean it to remove any larvae and reset the trap.

Prevention

• Remove any screening on the doors or windows of your greenhouse that contains holes or tears in the screen. Replace them with tight-fitting 16-mesh screens. This prevents the pests from entering the greenhouse through the tiny openings in these areas. Discard any soda or beer cans immediately upon finishing them. Empty the trash in your greenhouse daily to prevent the pests from being attracted by fruit peelings or other rotting food scraps.