It would reduce bugs for sure! If your soil is acidic, it would raise the PH. If you have very alkaline soil it can be bad. Most wood ash contains a good percentage, about 25%, calcium carbonate, an ingredient in garden lime. If your soil is very acidic (5.5 or lower), amending with wood ash can raise your soil pH . On the other hand, if your soil is neutral or alkaline, to begin with, adding wood ash could raise the pH high enough to interfere with plants ability to take in nutrients.