For the past three weeks I’ve been out monitoring for cockroaches in public housing developments. In addition to the usual suspects, I found quite a bit of fly activity.
Last week, Brandy (a public health sanitarian in NY) e-mailed asking if I could blog on drain flies. To top it all off, I found this little gem in my hotel room this week! It’s fate…this week’s post is about small flies!
When I walked into my hotel room, there was a smell. Not a nice one. Any normal person would go to the desk and request a move. But entomologists are not normal. I knew this room had great potential for drain fly activity so I threw down my luggage (on the kitchen counter because I hadn’t inspected for bed bugs…yet) and grabbed my flashlight.
I sniffed around and determined that the stench was coming from the kitchen area. I checked the trashcan—pulling it out, looking under the lid, under the rim, under the bag, and in the cupboard where it had been stored. Nothing gooey there! Too bad—if it was a trash can I could have solved the problem with a little soap and scrubbing.
The next suspect was the drain in the kitchen sink. Bingo! The underside of the rubber splashguard was slimy and I could see rotting food in the garbage disposal. Then, to my delight, I looked up and saw that Drain Fly, flying around looking for rotting goo in which she could lay her eggs.
So what was my solution? It was midnight, so I put a stopper in the drain and filled the sink with a little water to make sure the seal was good. This cut off the source of smell. Then I went to bed.
The next day, I requested the hotel service the disposal—ideally this would involve scrubbing the splashguard with a bristle brush and cleaning the disposal and drain with an enzyme cleaner that would break down the gunk. Two weeks ago I heard another suggestion for cleaning disposals from a PMP—put ice down the garbage disposal and run it. Apparently this does a good job of breaking up any decomposing matter and washing it away.
So how do you use IPM to solve any fly problem?
1. Inspect and identify
There are different kinds of small flies that might appear in a multifamily property. It’s important to identify the kind of small fly first in order to focus control efforts. There’s no sense digging through trash looking for gunk if the culprit is a small fly that mistakenly came in through an open window.
In this post I’m going to discuss the control of Drain Flies (aka Moth Flies), and Filter Flies. Lots of common names, as a group they are referred to as Drain Flies. Adult Drain Flies are tiny (1/5 to 1/6 inch long), fuzzy, dark or grayish insects with the body and wings densely covered with hairs. During the day they usually hang out, but at night they are more active around the spots where they lay their eggs—usually drains.
Drain Flies reproduce in polluted, shallow water or highly moist organic solids. They spend their childhood in the muck, slime, or gelatinous film often accumulating on the sides of drains and overflow pipes in homes, or in sewage disposal beds, septic tanks, and moist compost. They have also been found in dirty garbage containers, rain barrels, and tree holes. Consider dirty garbage containers, wet lint under the washing machine, and even standing water in containers under houseplant pots. Quite the homemakers aren’t they?
There are three other flies that I regularly run into in multifamily properties—House Flies, Fruit Flies, and Mosquitoes. I’ll post more about these in the future. In short, for House and Fruit flies the source is usually more garbage-related than drain. Mosquito control is done outdoors and they should be kept out of the home using screens.
2. Determine if action is necessary
If you’ve found Drain Flies, you’ve probably found their source too—if not, keep looking. If you find a good breeding site where they’re flying around, action is necessary. Drain Flies do not bite humans but most people don’t want to live with them around. And as so many pests do, they indicate an underlying problem—rotting is not sanitary.
To confirm the flies and the source you may want to put sticky trap monitors over the drain overnight (unfolded and upside-down over the drain, but propped up on something so that it doesn’t stick to the floor).
3. Plan treatment and take action
Cultural control: Drain Fly control is almost all about cultural control. Focus efforts around where you find the flies, but while you’re at it, clean up all potential breeding sites too. Concentrate on eliminating muck and slime from drains in floors, sinks, bathtubs, etc., clean the drain pipes and traps. Focused cleaning efforts may need to be made daily for a week to break the life cycle and ensure all goo is gone.
Someone may need to show residents how to clean. I like this factsheet from SF Environment about low toxic, easy cleaning products (Download EasySafeCleaningFactsheet - English - 0409). Go to your local dollar store and note (or take pictures of) what residents can buy there so that you can suggest products that are easy to get. If there is a garbage disposal, does it work? Regardless, tell residents to use an old toothbrush on the underside of the rubber splashguard.
Harsh drain cleaners may be used in compliance with label directions, although they are not as effective as other means (see biological control below) and must NEVER be followed with bleach since Chlorine gas can be released if the two mix in the drain line. It’s less toxic to remove the drain trap and using a "snake" in clogged drain to clean the pipes. Finally, flush lines by pouring ¼ cup baking soda into drain, followed by ½ cup vinegar. After 15 minutes, pour a pot of boiling water down the drain.
If the drain flies are in a trash compactor room, clean the chutes and compactor room on a more regular and frequent schedule. Clean at least monthly, weekly for a persistent infestation since these flies can go from egg to adult in a week if conditions are right. If there are floor tiles around the infested drain, you may need to lift and re-cement them.
Mechanical control: Residents may use sticky traps or fly tape to catch some flies, but the infestation won’t be stopped until the goo is gone.
Biological Control: Finally a household pest for which we have biological control! Use an enzyme cleaner or microbe product that rapidly biodegrades the organic matter in the drain. These cleaners contain the stuff in nature that breaks down organic matter—the application just helps along the process. If you don’t know how to get a good cleaner for Drain Fly control, ask your PMP. Note that using harsh chemicals like bleach or a drain unclogger will make these natural cleaners not work. As always, follow the label.
Chemical Control: Pesticides aren’t usually needed for drain fly control and do not get at the underlying source. If your PMP recommends pesticides for Drain Flies, question him on whether non-toxic alternatives would be better both in terms of exposure to pesticide and sustainable control.
4. Evaluate effectiveness
If residents are still reporting these pests, keep cleaning daily. If the Drain Flies are gone, keep cleaning on a regular schedule. Sanitation is the foundation of structural pest control.
Thanks to Gil Bloom of Standard Pest Management in NY and John Gideon of General Pest Control Co. in OH for their insights. I also got some information from the factsheets produced by Ohio State University and the University of Kentucky.