i get it in the spring sometimes when the weather is very damp, my house is built against the side of a hill and the back gets musty smelling if it rains a lot. i've found that a product called SCD Bio-ag works great, its just a lacto-bacillus culture, you can buy a quart for around 20 bucks. put a teaspoon of molasses in a quart of water, add a half a cup of scd, wait till the next day, you got another quart of scd to spray all your plants with. its the same as people saying spray skim milk on your plants. skim milk has a low fat content so it doesn't promote anything else to grow, and the lacto-bacillus in the milk out competes anything else growing on your plants, then dies off. scd has no fat to begin with, and its pretty much pure lacto-bacillus, so it just cuts out all the bullshit of using skim milk.