cause you have vinegar out its powerful it won't remain forever though. when you throw it out it takes all odors with it. ive tried honey and water as well and it attracts flies as well. people also told me to use a drop of dish soap to hold flies but but they wont go for it. cider vinegar works the best but it doesnt smell great lol. all scotts soils are infested with the gnats. i do like scotts premium potting mix though so when i use it i microwave it first. now have gardeners gold and no flies without microwave.