Mar 26, 2012 – Coming From The Neighbors
QUESTION:
We have a commercial building that has an ongoing Fungus Gnat problem. The employees are telling me that they cannot take it much longer. There is a recycling center directly across the street and we are very confident it is the source of the problem. We find the live gnats in all the rooftop air conditioning unit filters everytime we look. No moisture visible around the A/C's. The A/C company does keep those disks in the drip pans. We have checked the entire 150,000 sq. ft. facility for moisture related problems repeatedly and find none. There are no potted plants in the facility. The customer has about had it. Any suggestions for us?
ANSWER:
I probably don't have any good ones. Fly control relies heavily on source reduction. You cannot stop flying things from flying, although fungus gnats are not strong fliers and shouldn't go far from where they are breeding. This time of year there could be plenty of outdoor sources for them as we come out of a wet period. It is tempting to blame the recycling operation, and my experiences with these facilities is that they rarely are anything but pretty messy. But, is there a chance that you could speak with the management of that recycling center and be allowed to look around there as well? If your customer is getting so many fungus gnats from the recycling operation that they are in agony, then there should be plenty of fungus gnats at the recycling center for you to pin down that place as the source. If you are allowed access, and it would take some real diplomacy on your part to sweet talk them into it, you may be able to find some likely breeding resources for the gnats that could be fixed.
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We have a commercial building that has an ongoing Fungus Gnat problem. The employees are telling me that they cannot take it much longer. There is a recycling center directly across the street and we are very confident it is the source of the problem. We find the live gnats in all the rooftop air conditioning unit filters everytime we look. No moisture visible around the A/C's. The A/C company does keep those disks in the drip pans. We have checked the entire 150,000 sq. ft. facility for moisture related problems repeatedly and find none. There are no potted plants in the facility. The customer has about had it. Any suggestions for us?
ANSWER:
I probably don't have any good ones. Fly control relies heavily on source reduction. You cannot stop flying things from flying, although fungus gnats are not strong fliers and shouldn't go far from where they are breeding. This time of year there could be plenty of outdoor sources for them as we come out of a wet period. It is tempting to blame the recycling operation, and my experiences with these facilities is that they rarely are anything but pretty messy. But, is there a chance that you could speak with the management of that recycling center and be allowed to look around there as well? If your customer is getting so many fungus gnats from the recycling operation that they are in agony, then there should be plenty of fungus gnats at the recycling center for you to pin down that place as the source. If you are allowed access, and it would take some real diplomacy on your part to sweet talk them into it, you may be able to find some likely breeding resources for the gnats that could be fixed.
However, I have not started to hold my breath on that one. So, we'll move on to dealing with these gnats at your customer's facility. I know that it does not take many fungus gnats up your nose to be an intolerable problem, and these tiny flies can be pretty determined and annoying. It even seems as though they are drawn to breath, and make the effort to fly into your face. So, is this ongoing fungus gnat problem one where there are thousands of the flies in the building or just that onesy twosy gnat that finally picks the last nerve? For occasional gnats it could well be a few that live in the mulch outdoors and make it in when doors are opened. For thousands then obviously some hefty breeding source is nearby.
If you are resigned to dealing with the adult gnats then your options are really limited. I am not a great fan of pesticide applications for gnat control. You can kill all the adult gnats with a fogging of pyrethrum, but this is only a stop-gap measure designed to give relief while you find and correct the breeding source. Surface applications of residual insecticides may kill some adult flies but again it is going to be very temporary if successful at all. You could consider placing UV light traps throughout this building, and these are going to catch fungus gnats. You don't indicate what kind of commercial building this is - office, manufacturing, distribution - or if the employees being bothered are sitting at desks or working in a warehouse. This could definitely affect what options will work.
There really are no traps designed specifically for fungus gnats, and no baits or other attractants to draw them to a point. The UV light traps will be helpful. You might even consider placing plenty of large yellow sticky traps around the office area, and inspect them in a week to see how successful they were at drawing and capturing gnats. Yellow has traditionally been the color believed to be most attractive to flying insects, although Pest West is coming out with their BLUE Fly Baiter that the believe is more effective at attracting and capturing house flies, phorid flies, and some other flies.
I would not abandon the hunt for the source, nor dismiss the possibility of inspecting the recycling center and hopefully making some fixes there that could reduce the breeding potential, if that turns out to be the actual source.
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