Pestworld Magazine Focusing on the Business of Pest Management
FLIES
My client keeps finding small flies dead around their indoor house plants. the flies are about one‑eighth inch in length, with dark wings and a light colored abdomen. they do not look like fruit flies or drain flies, and I cannot find evidence of the flies anywhere else in the home. any thoughts?
It sounds like your client may be dealing with fungus gnats (family Sciaridae). these are non‑biting flies that are commonly associated with plants grown indoors. Female fungus gnats lay their eggs in wet soil where the larvae hatch and feed on algae, fungi and plant roots growing in the top few inches of dirt. After a few weeks, adult fungus gnats emerge and the lifecycle continues. Fungus gnats can become a problem indoors when house plants are overwatered, which allows fungus to grow in the potting soil. I would inspect your client’s house plants for signs of excess moisture in the potting soil. If you do find fly activity or fungal growth, you should instruct the homeowner to allow the soil to dry in order to correct the issue. It is also possible that these flies could be breeding outdoors in areas where constant shade and wet soil provide an ideal environment for fungus gnat larvae to thrive. therefore, you should also inspect the exterior landscape of the home for signs of excess moisture that may need to be addressed as well.
What are rattailed maggots?
The rattailed maggot is the larval form of the adult drone fly, a syrphid fly, of either species Eristalis tenax(Linnaeus) or Eristalinus aenus (Scopoli). Adults are so named because they resemble the male (or drone) honey bee in action and appearance, although the drone fly has just one pair of wings. The drone fly was introduced into North America sometime prior to 1874 and both flies are now common throughout all states. These flies are attracted by colorful flowers (especially yellow) as well as by odors.
The larvae of these flies are aquatic, rattailed maggots and are so named because of their appearance. The cylindrical, grub-like body may be up to 20 mm long with a very long tail-like breathing tube 30 to 40 mm in length. This hard-bodied life stage is resistant to crushing. Enclosed within the hardened skin of the last larval stage, the pupa appears a little shorter and fatter than the mature larva.
Rattailed maggots feed on decaying organic matter in stagnant water or moist excrement. Rattailed maggots are very rarely pests. However, occasionally, larvae appear in large numbers in dung pits or animal waste lagoons. They pose little threat to man or animals. However, in a few rare cases, intestinal myiasis (infestation by fly larvae) has been reported.
Drone flies have an unusual and little-studied life cycle. The female fly lays 4 or 5 eggs on or near contaminated water, sewage or other decaying organic matter. The larvae hatch from these eggs and then give rise to 7 to 30 daughter larvae in a bizarre parthenogenetic reproductive cycle. This method of reproduction may last for some time, but periodically female and male flies are also produced. Larvae can withstand many adverse conditions but are usually eaten by other fly larvae. Pupation usually occurs in a site drier than that in which the larvae developed.
Adult drone flies have never been implicated as disease vectors and usually do not become a problem if sewage and manure are not allowed to accumulate in pits, ponds, or streams. Client education and proper manure management will most often take care of any drone fly issues.
Our firm often gets requests to perform flea treatments, but we’re not sure what the service would entail. What can a pest management firm do to help control ticks on a residential property?
Most ticks prefer shaded habitats with relatively high humidity and do not survive well in areas with direct sunlight. To take advantage of this behavior, most pest management professionals approach tick control by focusing on the areas of a property where ticks are most likely to be encountered. Since ticks will rarely infest a well manicured lawn, the interface (called the ecotone) between the lawn and natural, wooded, or weedy areas is where the application should be focused. Some PCOs will use a high volume sprayer, to create a tick free “buffer zone” between the tick-free lawn area and infested natural areas. Many will also use granules for this treatment in conjunction with the liquid application. It’s important to find a properly labeled product to use for this treatment and make sure that you have the proper licenses/certifications to make pesticide applications away from the structure. The rules regarding licensing vary, so check with your state lead agency to determine what is required in your state.
In addition to the treatment described above, an important part of a tick management program is communication. It is good practice to recommend that your customer reduce the amount of weedy or overgrown areas on their property and limit their exposure to infested locations. Repellants containing DEET can be highly effective when used according to label instructions as well.
I have a ground floor apartment unit that has an infestation of small flies, they seemed to be concentrated around the diaper pail, but even after the customer removed it, the problem persisted. The flies look similar to fruit flies, but they don’t have red eyes. What can I do to control this pest?
The fly you are encountering is probably a phorid fly, also known as a scuttle, or humpbacked fly; both are common names for flies in the family Phoridae. These flies are sometimes confused with fruit flies because of their size and coloration, but there are a few simple identifying characteristics that can be easily recognized in the field to help you determine the difference. First, eye color can be tricky. Most people commonly associate red eyes with fruit flies, also called vinegar or pomace flies (family Drosophilidae), but not all fruit flies have red eyes, so using eye color is not as helpful as many people think. There are two easier ways to determine the difference. One approach is to observe the general shape of the insect. Phorid flies have a more humpbacked look, hence their other common name. Next, take a look at the fly’s rear legs. The section of the leg closest to the thorax is called the femur (analogous to the large leg bone connecting the hip to the knee in humans). Phorid flies have an expanded and flattened femur.
As for the infestation that you are observing in the apartment unit, it makes sense that the flies were hovering around the diaper pail. Phorid fly larvae live in and eat decaying organic matter and are often associated with contaminated soil adjacent to broken sewer lines. A diaper pail full of soiled diapers will probably provide a suitable secondary food source, but the chances are the problem is more complicated than that. Have building maintenance contact a plumber that is capable of identifying cracks or breaks in sewage pipes running beneath the slab. Often, phorid flies will breed in the contaminated soil and find their way into the living space through cracks, expansion joints or bath trap openings in the slab. If a broken pipe is found it, should be repaired and the contaminated soil should be removed and backfilled before replacing the slab.
I work at a cranberry production facility in which flies are very bad and found flying higher than one would expect from fruit flies and house flies. The flies congregate and fly around and land on white fluorescent ceiling lights. This is a regularly cleaned and sanitized stainless steel area in the cranberry processing facility. I never use pesticides or chemicals in this area. Do you have any suggestions as far as other possible control methods?
Since fruit flies especially are lower weight and less efficient fliers, typically they cannot fly this high of their own accord. The times we have seen flies flying higher than what their behavior and biology in textbooks would suggest was generally when they were either being transported by a conveyor belt, by the product on the conveyor belt, or by wind currents of fans and ducts within the facility.
Lights are a problem with most flies since they are positively phototactic (move to light). Can you switch the lights from white or fluorescent to yellow? (Flies do not perceive yellow wavelengths of light.) To prevent them from getting up that high in the first place, keep them low by using non-pesticidal fly light traps near the base of the conveyor. Also, encourage better sanitation measures around this product entry point on the conveyor. In addition, consider increasing air currents by applying a fan to keep the flies low.
I have a new customer that hired me to get rid of their cluster fly problem. My only concern is that it’s already winter…am I too late to do any good?
You are correct that you would have been much better off had they called you 2-3 months ago. Cluster flies are a group of 6 North American species in genus Pollenia and although they belong to the same family as blow flies, they are a different kind of pest. Cluster flies enter structures in the fall with the intention of overwintering in your warm house, preferring attics, structural voids, closets, windowsills, underneath clothes, picture frames, behind curtains, and other areas that are dark and protected. Once they have already penetrated a structure, like they have in your situation, things are quite difficult.
Fly control often centers on locating and removing breeding materials, but unfortunately that doesn’t help with cluster flies as eggs are laid in soil and maggots develop inside earthworms!
The two best forms of control are preventative: a thorough sealing of cracks, crevices, and other entry points into the structure, and a treatment of exterior surfaces that catch warmth and likely overwintering sites in the home with insecticides (tpyically dust formulations). Since those are not feasible options for this winter (though taking care of both of these by late summer next year could go a long way in reducing or preventing next year’s deluge), you are left without too many options. You can install ILTs in areas where they are found, physically remove them (vacuum with HEPA filter), seal off infested areas from the rest of the structure, and use insecticides. Treatments made after the flies have entered the structure can reduce populations but are unlikely to eliminate them.
These flies are quite annoying and can be numerous (hundreds to thousands) but they do not cause damage or transmit disease. They will likely stop being active in the coming days and stay that way until spring. When they do become active again they will attempt to flee the structure and probably be sluggish and easy to catch and dispose of in the process.
I recently got called out to a major small fly infestation in a first floor apartment and figured out that phorid flies are the problem. What’s the easiest way to determine the source?
Phorid flies breed in moist organic matter, which can be plentiful and available in numerous locations in and around an apartment building. The fact that only one apartment appears to be infested will help narrow it down, unless neighboring units are empty, non-responsive to such issues, or the apartment in question just happens to be the easiest way for the flies to surface. If you put fly boards around the unit, you can probably narrow down the general point of entry.
Consider all possible breeding sources and try to tick them off the list starting with the most likely and easiest to determine. Are there any obvious sources of decaying organic matter in or around the unit like visibly dirty drains, compost containers, overwatered plants, animal carcasses, dumpsters, garbage and recycling cans, grass clippings, organic debris under or around appliances, or a downspout causing an abundance of water outside the unit? The most difficult phorid fly problems are associated with plumbing problems like broken drains pipes under slab floors. Of course, these aren’t easy to check but there are a couple of tricks that can help you determine if that’s the source of the breeding material. Put pieces of clear tape sticky side down over drain openings or floor cracks while leaving some space in between them so air can still flow. This will catch adult flies as they are traveling between the breeding source and the rest of the apartment to help you pin point what is sustaining the infestation.
