That's really the trick it seems,,,, not that I have mastered it, but to knock out bugs before the problem gets bad. A good preventive point is always to spray your plants right when you start flowering. I like to do my last spray before flowering starts with a neem product. Your going to shit can all them fan leaves by the end of it all anyways. And neem is great an anti-feed which will help with them finding the food source. But it's easiest to spray your babies with like say azamax, is when they are smaller. Less leaf for bugs to hide in, and less leaf to cover with the spray. As long as they are big enough, big being well rooted, happy plants. Do a three spray routine, like every 3 days. Just don't start with the max amount, try 3/4 strength, till you see how they take the spraying. I always do a spraying routine before I start flowering. Isn't alot you can do if your real close to harvest, that green cleaner, or even safer soap. I like to spray safers and wait 15 minutes then rinse with water to wash off the bugs. Then get them buds in a dry place. Never spray and turn on your lights. Spray when they go out. Run a dehumidifier incase mold spores are around.
Everyone,,,, Keepem Green