It looks like you have a lot of trees around so I'm sure when there are storms that makes it a lot tougher. Here in Arizona we don't have rain coming down right now so it is a lot easier to control. My biggest problem recently was a lot of pollen coming off a tree in the neighbors yard which threw some stuff off.
Once monsoons hits I have to be on it a little better because the rain will throw the chemicals off.
Trees can be a pain, mostly at the end of the season.