[Fly Control] Managing Household Flies

Many species of flies will inhabit, live in and thrive in our customers’ homes. In one home there may be a dry sink drain trap, in a seldom used bathroom, that is providing a direct flight path for moth flies into the living area, while in another home a rotting bag of potatoes is serving as a breeding source for fruit flies in the pantry. In this article we’ll take a look at some of the major household fly concerns that occur, how to analyze these situations and ways that you can provide effective solutions in addressing these concerns.

When investigating all calls involving flies in homes I always try to determine the answers to four key questions in order to successfully solve the concern:

• What species of fly are the pests?

• Where did they come from? (Or, where are they coming from?)

• Why are they there?

• How are we going to get rid of them?

IDENTIFICATION. I’ll be the first to admit that I’m not the best taxonomist when it comes to identifying flies. However, if you’ll study the excellent reference materials that are available today, such as PCT’s Field Guide for the Management of Structure-Infesting Flies, you should be able to accurately identify the majority of the common fly species that you will encounter in homes. If you find a fly species that you aren’t familiar with, it is important to obtain several samples, in good condition, and have them positively identified. If you really don’t know what the critter is that you’re after, then it can often be difficult to determine exactly why they’re there, their habits and the best control methods to implement.

SOURCE AND ATTRACTION. Always remember that all flies need a moist organic source in which the larvae will develop. This "organic source" may vary greatly depending on the species of the fly that is involved. For example, cluster flies may be living all summer in the woods surrounding a home where their larvae develop in earthworms. Then in the fall, they may migrate in extremely large numbers to homes that provide suitable overwintering sites. Flesh flies may be swarming all over the interior living area of a home and coming from the carcass of a squirrel that fell down the chimney, a rat that died in a wall void or a dead opossum in the crawl space.

CONTROL. After you’ve got the critters identified, figured out where they’re coming from and why they’re there, you’re going to be facing the question: "How are we going to get rid of them?" Your first response shouldn’t be to grab a can or tank of insecticide! Take the time to think of what steps must be taken to gain long-term control and prevent recurrence.

If applicable, always attempt to first eliminate any fly breeding media within or under a structure that may be serving as the origination of infestation. This may simply involve cleaning a trash receptacle, changing the watering frequency of houseplants or routinely changing out the bedding material in the hamster cage. In other cases this may be much more involved, such as in a case with phorid flies breeding in "organically enriched" soil from a sewer leak.

If flies are entering into the structure from the exterior, determine if you can modify the conditions outside to eliminate those breeding sources. This may include such things as removal of animal waste from the yard on a regular basis, routine cleaning and/or relocating the trash cans next to the back door. Also look at the structural integrity of the home and look at possible exclusion needs. Are there screening and/or caulking needs that you should recommend? Are garage or house doors routinely left open?

Once you’ve reviewed these areas, then it’s time to think about the effectiveness and practicality of other control methods. These may include the use of a vacuum with a hose attachment, placement of sticky boards by windows, the installation of flying insect light traps or simply using a "good ole" fly swatter. In the case of flies breeding in drains, effective long-term control may include the treatment of those sites with a biological product to eliminate the "organic sludge accumulations" within the drains.

If the use of insecticide is warranted you should look at both short- and long-term control objectives. The use of a pyrethrum aerosol product will normally provide excellent contact kill of adult flies when conditions are present that allows for its use. Insecticide dust application of wall voids and exterior cracks and crevices may be beneficial when addressing a late season call on large overwintering flies. On the other hand, the exterior application of a microencapsulated residual insecticide on exterior siding and eaves may prove extremely beneficial when making a preventive treatment in the early fall to a home with a history of large overwintering fly populations. In certain situations, the use of fly baits on the exterior of a home may also prove beneficial in reducing populations of certain species of adult flies.

The following is a review of several fly case studies that I’ve encountered over the years.

THE MOUNTAIN RETREAT. One day in early November I received a call from the wife of an old friend. Several years earlier they had built a nice vacation home off of the edge of the Blue Ridge Parkway. During our initial conversation she told me that they had such a severe problem with overwintering flies and ladybugs that they were thinking that they might sell the property if the problem couldn’t be controlled. I told her to hold off in calling a real estate agent until I could come up and take a look at the situation. When I arrived at the property I found a large two-story contemporary home painted a light beige.

The home was situated on the southern exposure of the mountain overlooking an old apple orchard. When I entered the home I was amazed to see literally thousands of flies of several species. After completing my inspection and discussing the findings, I implemented the following plan of action:

I treated all attic space areas with insecticide dust; injected insecticide dust into all visible cracks around both interior and exterior sides of window casings. I spot treated around all interior and exterior window casings with a microencapsulated liquid residual. I used pyrethrum aerosol in both the attic and areas of the living area where large numbers of adult flies were present. I treated exterior siding and under eaves with a microencapsulated residual liquid insecticide. And finally I swept and vacuumed up all dead flies and cleaned all counters, tables and any other exposed food contacting surfaces in the home.

My recommendation following treatment was to wait until the next late spring or summer and aggressively caulk and seal all cracks and crevices. I also recommended that we provide a preventive exterior treatment in mid- to late-September of the next year. The reason for this suggestion was that many flies and ladybugs that are attracted to a structure will spend a large amount of time during the warm afternoons of fall on the exterior siding prior to moving into the wall voids and/or interior living area prior to winter. I also suggested that they may consider a darker paint selection the next time the home needed painting because certain light colors may prove more attractive to flies and ladybugs than darker colors.

THE FLIES AT MY BUDDY’S HOUSE. My buddy Keith worked hard, saved his money and built a comfortable home that has a driveway that’s about a mile long. The first summer after he moved in he called saying that he was being invaded by flies. They were constantly all over the outside of the house. Upon arrival I found several species of flies present with the predominant species being the common house fly. With a little investigation we determined that there was a large chicken farm about a half- mile upwind from his property.

In this situation I believe that the flies were traveling from this farm and harboring around the shaded areas of my friend’s home. In this situation I provided an exterior treatment of the home using a microencapsulated residual insecticide and installed multiple hanging fly bait feeding stations. Now that Keith and his family have lived on this property for several years they have several horses, some goats and usually at least one or two dogs. Unfortunately for all of them the battle with the flies starts back every summer at this location.

OUR MASTER BATHROOM. In the master bathroom of our home we have a tub and a shower. We almost never use the tub but use the shower on a daily basis. A number of years ago I was going to take a shower and noticed a moth fly on the wall of the bathroom. As most entomologists worth their salt would do, I hunted up a vial and caught it. As the number of moth flies grew so did my loving spouse’s insistence that I solve "the problem." With great reluctance I turned on the faucet in the bathtub and refilled the drain trap with water.

Moth flies will often live in the sanitary sewers in large numbers. They can also live in the organic slime or "sludge" that can accumulate in drains. If you are experiencing a problem with moth flies and can’t put your finger on the source you can eliminate specific drains by placing a plastic cup with a sticky insect monitor over each drain to eliminate potential points of infestation. (A little cooking oil poured into a seldom used drain after it is refilled with water will aid in reducing the evaporation rate.)

"GNATS" EVERYWHERE. One day we received a call at our office from a lady who called and said that she had a rat in her house and had gnats everywhere. Once on site I found the home to be an older two-story frame house with a half basement and a half crawl space. The "gnats" were randomly scattered throughout the first floor of the home with very few on the second floor. I recognized the critters to be phorid flies and headed for the basement. Interestingly, I initially didn’t see any flies in the basement. This was a different story when I opened the crawl space door.

I crawled in about six feet and stuck my head up under a big flexi-duct truck line. Just as I got my head poking out from under the other side of the flexi-duct a rat ran by about three feet in front of my face. I then panned the remaining visible area of the crawl to see hundreds of phorid flies running over a great big wet spot in the soil. Directly overhead was a galvanized drain line from the bathroom that had a big hole in it. The bathroom waste was being deposited into the crawl space and the rats were entering into the home directly from the city sewer system.

The homeowner had the drain line repaired. We trapped the rats and made an initial treatment of the crawl space for the phorid flies. I informed the homeowner that it might be necessary to have the moist "organically enriched soil" removed from under the home if the fly problem continued. In this case the crawl space was well ventilated and the soil apparently dried rapidly enough that soil removal was not necessary.

CONCLUSION. Pest management professionals should be prepared to address concerns with flies that may be in or around the homes of their customers. Keep in mind that you should approach each situation that you encounter involving flies by answering these five questions: What are they? Where did they come from? (Or, where are they currently coming from?) Why are they there? And how are we going to get rid of them? If you accurately answer these questions you should be able to implement a successful plan of action to manage files in households.

The author is owner of McNeely Pest Control, Winston-Salem, N.C. He can be reached at smcneely@pctonline.com.

COMMON HOUSEHOLD FLIES (AND THEIR POINTS OF ORIGINATION IN THE HOME)

House flies may live in the organic material in the bottom of a kitchen trash can, directly beneath a leaking trash compactor or in animal waste in or under your customers’ home.

Phorid flies may thrive in waste-enriched soil in a crawl space beneath a leaking sewage drain line or in the pet hamster’s cage bedding.

Moth flies may have direct access into the living area through dry drains. In addition, they reproduce quite nicely in the sludge accumulations in the “throats” of sinks.

Fruit flies may have a favored place of residence in the bowl of bananas present in the kitchen or the goodies left in the drain area of the garbage disposal.

Fungus gnats may be reproducing in moldy sliding door tracts, over-watered potted plants or decaying roofing material.

Flesh flies may be emerging from a dead squirrel in the chimney or dead rodents in the wall.