Gnats in Sinks

While there is some variation surrounding what insects constitutes gnats, for our purposes we will address only those small flies that are non-biters and are likely to be pests within homes and other structures.

The gnats most likely to occur in sinks and sink drains include fruit flies, moth flies and to a lesser degree phorid flies. The breeding and developmental sites for these small flies, often called sink gnats, are varied, but for the most part include habitats that stay moist and contain decomposing waste components.

Signs of Gnats in Sinks

The most obvious signs of gnats in sinks are adult flies found inside the sink drain. As with most gnats, the observable sign of gnats in the drain are the adults hovering around the sink drain and food scraps left in the sink. Here are some methods that work well to actually observe gnats in the sink:

• If you suspect gnats are around the sink or in the sink drain, wave your hand or gently pass air over and into the drain. If gnats are in the drain, they will exit the sink drain and come out into view when disturbed by air movement.

• Sometimes running the garbage disposal will result in gnats being disturbed and flying out of the disposal drain.

• If dishes are left in the sink, sometimes fruit flies, moth flies or phorid flies that came from the sink drain may get caught in dishes, cups or plates that are wet and contain water.

• Adult gnats may be seen feeding on food scraps left in the sink and might also be seen resting on the walls in bathrooms, kitchens or near other sites where organic breeding materials are found. Fruit fly and moth fly gnats are sometimes attracted to walls that are light yellow in color.

• Place tape or an adhesive pad over the sink drain, leaving it in place overnight and then inspecting to see if any adult gnats are stuck to the tape or sticky pad.

• While very difficult to see, the tiny gnat larvae may be seen using a video camera that is placed into the infested drain and “snaked” through a plumbing pipe to locate a leak that sufficient to enable phorid flies and moth flies to develop.

Develop a Control Plan

Gnats in sink drains are very difficult to control with insecticides, only. The best course of action is to: contact your pest management professional (PMP) and request he or she conduct an inspection to correctly identify the species of gnat(s) and develop a control plan to fit the needs of the situation.

Correct identification of the kind of gnat causing the problem critical since different species of sink gnats require different control techniques. Unquestionably, sink gnat control is not a “one size fits all” kind of approach.

How to Get Rid of of Gnats in the Sink

Sometimes the gnat problem may be something the homeowner wants to try on his or her own. While self-help efforts that work to control gnats are very time and labor intensive, some tasks that are required include:

• Using an integrated gnat management program that involves physically cleaning drains with a recommended biological (microbial) drain cleaner or steamer machine to remove as much organic material as possible.

• Use a long-handled cleaning brush to physically remove organic matter that clings to the side of a drain and is the source of food for larval gnats. By removing all of this organic matter, the life cycle of sink gnats is broken since the gnat larvae will die, resulting in no further population development and reproduction.

• Repair sink drain lines that may be leaking. This is a job for professional plumbers and not the average homeowner.

• Removing food scraps and leftovers from the sink.

• Using and maintaining effective and attractive gnat traps available at big box stores or you local pest control provider.

• Do not stop looking for gnat sources one development source is found. Generally, several sources are present and overlooking even one can lead to control failures.

• Control any adult gnats found in or around the sink using a fly swatter, portable vacuum or an insecticide registered by the USEPA for control of sink gnats.