NDSU Extension - Ramsey County


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March 4, 2013 Agriculture Column


Well a little snow we got.  I was up pretty early yesterday blowing snow to get my wife to work.  It is not that we could not have made it but once it has been driven on it is almost impossible to move unless a blade or scraper comes along.  The snow at that point, yesterday, was about 6 inches as reported by everyone I had talked to with another blast coming in as I write this note today.  Over the weekend, I was fishing at Stump Lake, and had a pickup drive fairly close to me to fish.  He walked over and asked how fishing was and when he spoke I recognized his voice but looked so different than I remembered him.  We had a very nice visit and talked about our jobs and how our families are.  I usually get irritated when someone gets so close but in this case it was really great to get to see an old friend.  The unfortunate part is if he would have drilled in without saying hi I would have not had a clue who he was.  My how we all change over time.

Attic flies or 4-5 spotted attic flies as they are called???

Cluster flies are simply a type of fly, not too much unlike the typical fly you find up against your window in your house. These cluster flies are born out of earthworms, if you can believe that, and like to overwinter in protected areas. Most commonly, these cluster flies move from the ground to your attic for the winter; thus, the common name they have of attic flies. By instinct, they seek shelter away from the elements, such as in the fall when it gets cold. This is one time when you might see flies swarming your attic. They also tend to appear in early spring when things start to warm up. When you notice this, it’s time to think about extermination. But do you call the exterminator or can you get rid of attic flies yourself? Let’s consider your options.

Of course, if your attic is filled with cluster flies already, you aren’t immediately concerned with how to keep them out–a problem you should deal with later. Right now, you have to control the fly infestation in your attic directly. At this point, there is nothing really “humane” when it comes to controlling these little guys. They are pests, and unfortunately you’ll have to kill attic flies that have taken over. Here are a couple solutions:


  • Release a fogger in your attic to kill cluster flies: There are plenty of products on the market that help in getting rid of attic flies. A fogger chemical is an inexpensive and easy way to help you eliminate most of the flies. You may have to reapply a few times until the flies are no longer active.


  • Window fly trap: Made specifically for cluster flies and very useful for attics, a cluster fly trap like this one works by catching flies as they “wake up” and start moving toward the warming outdoors–windows or screen openings you might have in your attic. They are very effective, and are made to capture hundreds or even thousand of flies. Much better than a typical fly trap! 

    Prevent flies from getting in your attic
    Truly the best way to solve your problem with attic flies is to stop them from ever coming in in the first place. Your attic should not be a fly motel, so there should be no welcoming doors or windows for them to get in. It’s not always easy though to secure such openings, so perhaps you would benefit from a two-prong approach with the suggestions below:


  • Apply insecticide to the outside of your attic to prevent cluster flies from coming in. Do this in the summer or early fall at the latest. Remember, attic flies want to “cluster” indoors when it starts to get a lot cooler. Spray as best you can around your roof, chimney, eves, ventilation holes, etc. The attic flies will be repelled by the chemicals and retreat from going in your attic.
  • Close up openings where attic flies get in. Use caulking to seal up gaps, cracks and other wide seams that lead into your attic. Patch up torn screens and seal gaps around electrical or plumbing penetrations. Attic flies are very good at finding any available gap or hole in your attic, so be sure to seal up the thinnest of joint gaps such as between trim and siding and particularly at the eaves.

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