 and keep from coming back that won't hurt the roof so well you took the first step by by getting rid of some of those trees you'll have more sunlight and that will have a natural effect sort of a natural mildew side effect the other thing that you can do is you can treat that wood with a mildew side there are a number of roof products out there that will work jomax is one 30 second cleaners is another and these are products that you can use a spray hose applicator with so you kind of shoot the roof and saturate it and let it work for a while it's not an instant thing you know you have to