Best Way to Kill Flies in the Greenhouse or Barn – A DIY Flytrap

I built this fly trap just like the ones you see on the Internet all the time. I was running out of time as I left the house and mixed up the liquid lure from memory. It was not the lure I had written down. Oh well…now I can do an experiment comparing the different lures and give you the results.

Why not just buy a fly trap and be done with it? I may do that in the end, but I love a good DIY solution that lets me use up plastics in my recycling bin. By mixing my own lure I also know if I can compost the flies whereas I have to trash the store-bought lures because I don’t know if there is poison in them or not. I have heard good things about the store-bought traps that are reusable, and easy to hang, so that might be the next-best thing to making my own.

For this trap lure I mixed 1 cup of white sugar with 1 cup of apple cider vinegar. I cut the 2-litter across at 7″ from the bottom/table top. I’m going to take the plastic ring off the bottle neck of the next one just in case that is giving the fly a target to aim for, and I will cut closer to where the bottle begins to bend to see if that gives a slightly better connection point for taping back together. The next trap will use 1 cup sugar, 1 cup water and 1 teaspoon of yeast.

I have been having problems with flies for over a month. It started in the fall of 2020 just a few months after the Greenhouse was finished. I had over a hundred flies November 5th. They were all on the outside of my barn warming themselves on the dark green metal as fall began to blow in. I don’t know if they were all coming from the chicken coop or if that is normal, but I was relieved that they were outside. I shouldn’t have been so relieved.

Two weeks later on November 19 there were flies inside. Not as many as outside…I guess only a portion found their way inside.

The flies disappeared and then 9 days later they were back with a vengeance. The sunny day brought the greenhouse temp up to the 90’s even though it was chilly and windy outside. It looked like hundreds this time. The sound was disturbing. Sort of like being inside a metal bee hive, but a much softer sound…flies are lazy compared to bees!

Before heading home I placed a solar light next to the trap to make it more attractive to insects as it gets dark and cold each night. I only saw one live fly in the greenhouse, but I don’t trust that they are gone yet. It was 34 degrees outside, and inside was 46 degrees…but on a sunny day it can get much, much warmer. I don’t know where they are hiding, but I am ready for the next big fly festival.

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