The issue of flies in drains has come up several times in the last few weeks, in calls from hospitals, nursing homes, and housing subdivisions from Virginia to Iowa. The situation is generally the same: there are numerous small flies in one or more rooms or houses or areas of the building, and they seem to be associated with sink or floor drains. The questions are also similar: How can we get rid of them? And my response is always the same: What are the flies? That question often frustrates the caller because it sounds so "academic"--isn't that just like those university people to want to know what kind of fly it is! It really does make a difference; the difference between simply cleaning or removing accumulated organic matter that may be clogging the drain, to bringing in someone with a jackhammer and a shovel to remove the 4 inches of concrete above the drain pipe so that the break can be located and fixed (Cincinatti hospital, Virginia nursing home). It can make a big difference.

Case #1 - Hospital. Employees in Billing Office (basement location , no windows) have complained for months about small flies that seem to be everywhere---on their desk, in the files, in their coffee cups, in the restroom--just everywhere. The first accused was the potted plants (hospitals are full of these)--fungus gnats, then the drains in the bathroom--drain flies, then food left in waste baskets--fruit flies. When none of the attempts at control worked they called someone--and he wanted a sample of the flies. They turned out to be phorid flies, and these flies are associated with decaying organic matter, and not clogged drains, and not the soil in pots, and not decaying fruit. Unfortunately, the phorids were coming from a disfunctioning drain and trap system in the autopsy/morgue rooms which were close to the Billing Office (there is a subtle message in that). With all the fans and activity in the autopsy room (and the fact that the people there had become accustomed to the flies), the flies went unnoticed. To solve the problem the drain system had to be replaced.

Case #2 Nursing Home. Persistent complaints about flies in a washroom and in patient rooms prompted the Nursing Home to contact a pest control company. They tried treating the drains, removing potted plants--the usual suspects. Finally, they called someone! Once we determined the flies were phorids we knew the problem was not going to be solved with chemicals or cleaning drains, or tossing out the plants. With a jackhammer the floor in the washroom was opened to expose a drain pipe that had decayed so much that the soil was soaked and supporting a large population of phorids. The soil had to be removed and replaced, the pipe repaired, and the floor redone.

Case #3 Housing Subdivision. Complaints from several homeowners of small flies in the basement during the summer. The pest control operator that was called identified the flies as phorid flies and suggested that there were clogged drain problems or broken sewer line problems. Before they started digging up backyards and sewer pipes, they called someone. The flies in this case were fungus gnats and not phorids--but they may have looked like phorids. The problem was not broken sewer lines but poor drainage around the basements which resulted in moist soil at the slab/foundation union. The fungus gnats found enough moist soil to survive during the warm months.

Phorid Flies:

These small black or yellowish brown flies are attracted to decaying (with an odor) organic (usually highly organic) matter. They can infest sites deep in the ground, they can persist through the winter, they can occur in large numbers or be sporadic. Identification of phorids is made by looking at their wings, which have dark veins only near the base, or observing that they have a rather "jerky" running behavior. Phorids may fly far from the site of infestation, but will usually be concentrated where the odor is strongest. Chemicals rarely will solve the problem. The cause must be located and the soil must be removed.

Fungus Gnats:

These small black flies are attracted to moist to wet organic soil. They are weak flyers and usually do not move far from the infestation site. The wings of these flies are often dark brown to black. They are primarily found in the summer. Often (but not always) these flies are associated with potted plants or soil that has only limited organic matter. They are not associated with sewer lines or clogged drains. Removing the source of the moisture will usually solve problems with fungus gnats, the soil does not have to be excavated.

Fruit Flies:

These small flies with the red eyes and yellowish brown bodies are common during the weeks of late summer. They are associated with decaying fruit--usually recently decaying fruit. They do not breed in clogged drains or in organic soil.

Drain Flies:

These are also called moth flies because of the long hairs on their wings, perhaps they look like small moths. These flies do not move far from the breeding site, they don't fly well at all and usually spend their time resting on the wall close to the site they are infesting. As their name imples they are associated with clogged drains, but also to organic matter that may accumulate around sinks and other fixtures in bathrooms. The larvae can survive some fairly strong chemical applied to the drains, so the best method for control is to physically clean (remove the stuff!) the drain. These flies rarely occur in large numbers, but may persist throughout the year in small numbers.


Indian Corn - Those decorative, multicolored corn ears that are common this time of year (maybe left over from Thanksgiving) are great, but keep an eye on them. Sometimes these corn ears will become infested with Angoumois grain moths. Small holes will appear in the kernels and you may see some very small, white moths flying close by. They will not infest other material, but they sure can have a good time on that corn.