Tried Insect soap for trees

I bought some insectisidal soap for the fruit trees, it's supposed to be safe for both environment and plants. It says to use every other week, but other places I've read about it say that it only work while it's wet, once it dries it's ineffective. We'll see... I sprayed the Cherries, apricots and blueberry plants with it, both tops and bottoms of leaves.