My plants, due to, I believe, some infested potting soil, became infested with fungus gnats. Seriously and terribly infested. It was horrible. I started using Pretty in Green Bti and it immediately controlled the fungus gnats. It did not immediately eliminate them. This is largely because fungus gnats are so prolific that it takes a good long while to eradicate them when you have an infestation as bad as my plants had. However, the eradication process really speeded up with two added measures. I started using de-chlorinated water when I mixed up my Bti and then let the "brew" sit for 24 hours. I believe the chlorinated water lessened the strength of the Bti. So, after using only de-chlorinated water and after adding the Bti and letting it sit for at least overnight to let the culture grow - well, it made a huge difference. My plants do not have any more fungus gnats and it is so wonderful! I continue to use Bti as a preventative measure at this point. So thankful for Bti and so thankful for Pretty in Green - an excellent company to work with. Thanks Pretty in Green!