Case Studies

Pests We Treat Case Studies: Drain Flies Infest Home in Matawan, NJ

Friday, March 15th, 2019 by Alfonso Reyes


I was contacted by a homeowner in Matawan, NJ who was suffering from a major drain fly infestation. Drain flies, also known as sewer flies, are classified as true flies — which means they have functional wings for flight and a pair of vestigial hind-wings for balance. With their short, hairy bodies and wings, they almost look like “furry moths.” Drain flies do not come up from your pipes or drains as you might suspect, rather they come from outdoors to the drain when they smell the organic matter they need to breed. Drain flies get into your home through those tiny holes and can transport bacteria in their bodies. To make matters worse, if you touch the bacteria, you might get sick!


Once I arrived at the property, I began to evaluate the situation. The homeowner insisted that I apply some insecticide to the walls in the basement since that is where he has had a major issue. Although the information the homeowner provided was extremely helpful and spraying insecticide sounds like a good idea,  I respectfully told him that I had to inspect the entire property first to find the source and thus apply an effective treatment. Even though you suspect that it might be one type of insect or the infestation is in a certain area, you should NEVER apply any type of treatment until you conduct a full inspection first. You could wind up treating the home for the wrong type of insect and then have to wait a while before treating for the right type of insect. During that time, the infestation could worsen and you’ll wind up with a much larger problem than you originally had. Conducting a full inspection first will confirm where the infestation is, what type of insect you’re dealing with, and how to treat it.

After doing a thorough inspection of the problem, I discovered that indeed the issue was in the basement by the water that stagnates in the French drain. You can see hundreds of drain flies larvae in the French drain. I proceeded to apply larvicide, which specifically targets larvae, to stagnate water on the french drain to eliminate the fly larvae and also applied fly bait around the area to control adult drain flies. Doing this method prevents the birth of any additional drain flies as well as eliminates the adult flies in the area.

I followed up with the homeowner three days later to ask how his situation was going. The homeowner was excited to announce that there were no more drain flies in his home and how grateful he was for our help.