Our homes are buttoned down for the winter. Screens have been replaced with storm windows, caulking around the house completed, and the weekend of Nov. 19 we had our first hard freeze. Temperatures dropped to the teens and daytime temperatures struggled to reach the freezing point.
Any remaining outdoor flies and gnats were frozen and most likely killed.
In our home, though, we have been plagued by tiny gnats. My wife was really annoyed as I made the horrific mistake of saying, “They are not bugging me; in fact, they seem to be bugging only you.” Grudgingly upon further investigation of these tiny gnats, I discovered they were Phorid Flies. My wife was not amused, and said, “I don’t care what type of flies they are. Get rid of these horrid gnats now.”
Phorid flies are also commonly known as humpbacked flies. The adult flies are about 1/4 inch in size and have a humpbacked appearance. Phorid flies breed in decaying organic matter of plant or animal origin. Control consists of eliminating or drying up the offending organic matter.
In our living room we have a large window. The window has a weep hole. Weep holes are design features that allow water to escape from a structure — whether it’s a window, sliding door or other areas in the home. Weep holes must remain open for water to drain. Weep holes can become plugged over time with dust and other debris which create organic matter. Sure enough, there were Phorid flies congregating by the window.
Using a 2% bleach solution and a syringe, I judiciously cleaned out the weep hole. Ah, I thought to myself, problem solved. Not so fast — after a few days they were showing up in other areas of the home.
They can also breed in drainpipes. After checking and cleaning out all our drains by the sinks, shower and bathtubs, I was mystified. Where were they coming from? Walking back to the laundry room, there they were in the drainpipe of the washing machine. Finally, after cleaning out the drain, the problem was completely solved.
Besides Phorid flies, another common wintertime gnat is the Fungus gnat. Adult Fungus gnats are delicate, dark brown or black flies that are approximately 1/8-inch long and do not have a humped back. Fungus gnats are usually noticed indoors when adults fly around light sources (e.g., windows, lamps), or when they fly around or walk across and rest on the soil of potted plants. They can become a nuisance when they are present in large numbers and fly around inside a home.
Fungus gnats are often more of a problem in the fall when houseplants that have been outdoors for the summer and have become infested, are brought back indoors. It may take three to four weeks of modified watering and use of sand/gravel to get fungus gnats in check.
Other houseplants and holiday decorations such as Poinsettias potting media often have high organic matter such as peat moss and composted bark. Fungus gnats are commonly associated with these especially if overwatered.
Like Phorid flies, control of fungus gnats is by modifying the environment. Keep the soil surface dry to eliminate favorable egg-laying sites for the insect. Do this by allowing the top inch of the soil to dry out before watering. Alternatively, you can water from the bottom to provide moisture for the roots while keeping the soil surface dry. In addition, you can cover the soil with a ½ to one inch layer of coarse sand or fine gravel which will help keep the surface drier and make the soil less attractive for egg-laying.
Another lesson learned: Never blame the spouse for gnat problems in the house.