Putting water in a ziplock bag for flies may sound like a good idea. But is it actually effective?
Many practitioners argue that it works because flies see it as a vast body of water, but this explanation is not backed up by significant evidence. And while a water bag may be effective for a particular area of your yard, it’s unlikely to reduce flies by the same degree as a large tank.
In addition to the myth that hanging a water bag on a ceiling is an effective repellent, there is no scientific evidence to support this claim. Researchers from the TV show MythBusters set up a rig with three chambers and released 5,000 flies into the first. They observed the activity of the flies in the other chambers and weighed the dead flies to determine whether they had been killed by the water. They found that the bag contained about 35 grams of water and 20 grams of flies.
Aside from being unpleasant, flies carry disease and can be extremely annoying. A water-filled ziplock bag may be a good way to keep them away. Although there is no scientific evidence to support this claim, many people swear by it and use it at their outdoor gatherings to protect their homes. The flies may not be able to see the water, but they will still be put off by the odor of the water.