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MASTER GARDENERS: No need to bring in the troops to fight fruit flies, fungus gnats

Fruit flies and fungus gnats often invade our homes in the fall when we bring in houseplants and produce, but that is not their only source. Eggs come on plants or fruit and vegetables we purchase as well as result from our own housekeeping practices. It takes know-how and good housewifery to deal with them both.

Fruit flies are little brownish flies about ⅛-inch long with a dark colored abdomen and typically have red eyes when they are alive and flitting around. Each female can lay 500 eggs and lives only eight to 10 days so there is a lot of potential for a need for birth control! They hatch from eggs on the surface of overripe fruit, and decaying vegetables but can be found in less obvious places.

You might find them near your munching-fruit bowl, on some countertop vegetables that you planned to use later in a day that turned into several days. You might find them in an empty wine glass, a beer or soda can you left behind a stack of books you were reading and forgot. They may be in some dishes left on the counter that didn't get taken care of when there was more to do than you could handle. They might be in sink gunk, the garbage disposal, or in an unwashed garbage container containing bits of wet garbage or liquid. They may be in your countertop compost container that didn't get cleaned the last time you emptied it. They can even fly to areas that don't contain these sources.

The key is keeping surfaces clean and with getting rid of suspect moist sources where they lay their eggs. So make some banana bread before you have a cloud of insects or freeze the bananas and make several loaves when you have time. You can also rinse fruit and vegetables when you bring them home in a 1-to-10 solution of alcohol to water to assist with getting rid of eggs. Police your living room for glasses or cans daily. Clouds of insects do not make for a pleasant atmosphere when you have guests or when your mother-in-law comes to visit.

Fungus gnats are ⅛-inch, dark-winged flies with long legs and antennae that flit around our house plants or even migrate to window frames. The adult females lay up to 200 eggs during their week to 10-day lifecycle. The eggs hatch into wormlike, translucent larvae that have a black head capsule. The live in the top 2-3 inches of the growing medium for two or three weeks before pupating. They feed on decaying and damaged roots and on dead leaves resting on the surface; they enjoy our 65-75 degree houses and thrive on organic growing mediums that stay too wet.

Control involves keeping the top 1-2 inches of soil dry prior to watering. Remove dead leaves or mulch from the soil surface. To detect the larvae, wedge thin raw potato slices in the soil and remove when larvae feed on them or use yellow, sticky traps (Gnat-stix) to capture adult flies.

You also may need to repot plants as old peat-based soils hold more moisture as they age.

This is the last column for 2018 and the Master Gardeners will not be monitoring the voice mail (218-444-7916) after this week. Please seek information from the University of Minnesota

Extension website——or ask a Master Gardener that you know for help during the winter months. Our Facebook page may also be of help,