Get Rid of Drain Flies

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Drain flies tend to appear rather mysteriously and suddenly, multiplying quickly and becoming a nuisance by their numbers. Drain flies originate in filth, and carry diseases that may possibly be transmitted to humans. The presence of drain flies in large numbers may also cause or intensify bronchial asthma.

Step 1)
The Drain Test

Drain flies are most active in the evening when they congregate around sinks and drains. Before treating for drain flies, you'll need to make sure your infestation is really coming from the drain rather than some other hidden source of moisture or decay. Fruit flies and Phorid flies are other types of small flies found in kitchens and bathrooms that may be easily mistaken for Drain Flies, and in that case the source is probably mold or rotting fruit, and the treatment would be different. To perform the Drain Test:

1) Right before bedtime, thoroughly dry off all sinks, bathtubs, and floor drain areas.

2) Place a strip of clear sticky tape across the center of each drain, with the sticky side facing down towards the drain. Do not cover the drain opening completely, or else the flies will not have an updraft on which to emerge.

3) Leave the sticky tape traps in place overnight or over the weekend if possible.

4) If you find flies stuck to the tape, you know that drain is indeed one of the breeding grounds for drain flies. If you do not find flies, repeat the test for at least 4 more nights to provide for variations in the breeding cycle.

Step 2)
Control Drain Flies with Drain Gel

Once you have confirmed the source of the infestation using the drain test, you can begin the process of eliminating organic materials that have accumulated on the sides of the drain, which are the source of Drain Fly harborage and reproduction. Do not attempt to remove these materials with bleach or hot soapy water, since these methods are not effective. Drain Gel is a product specially formulated for removing organic material from drains and it is proven safe for both sewer and septic lines. To use Drain Gel, follow these directions found on the product label:

  • PREPARATION: If drain is not regularly used, moisten drain by pouring 1-2 gallons of warm water into drain. For all applications, apply product at time of lowest drain use, ideally at end of day after the use of all cleaning and sanitation products has been completed.

  • START UP: Add four ounces to each drain in area. Apply around edge of drain, attempting to coat sides of drain. Repeat dosage daily as necessary, usually for 5-7 days.

  • FOR MAINTENANCE: Apply four ounces per drain every one to two weeks.

Step 3)
Space Sprays for Quick Kill of Drain Flies

Since it may take up to 5 to 7 days to see compete elimination with the Drain Gel, a space spray may also be used for quick kill of flying adults present in the surrounding area. One example of an appropriate space spray for Drain Flies and other small flying pests is Microcare. Apply Microcare according to the product label as follows:

1) Close all windows and doors and direct fog upward at a rate of 5 to 8 seconds per 1,000 cubic feet. Disperse in all locations.

2) Keep area closed for at least 15 minutes. Do not remain in treated area.

3) Repeat application as necessary, but not more than once every 7 days.

Step 4)
Don't Forget the IGR!

These days, a pest control treatment is not complete without the IGR. Think of an IGR (Insect Growth Regulator) as a sort of "birth control" for insects. An IGR disrupts the development of Drain Flies at the larvae stage, thus preventing them from becoming breeding adults. This prevents current and future infestations. Gentrol Aerosol is an IGR which can be sprayed directly inside of drains and along drain lines.

View our entire line of Fly Control products, including fly bait, fly traps, and fly lights

Related Articles:
Drain Flies Identification & Biology
Fly Light Traps
Fly Spray
Fly Zappers
Sticky Pheromone Fly Traps
Indoor Fly Control
Outdoor Fly Control
Natural Fly Control


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