I used to think spraying was only done when you saw a problem. I've learned, as you obviously have, the hard way. There was one shipment about three years ago that killed about 20 of my nicest plants. Now I spray on a weekly basis for rot and bugs get sprayed every couple weeks. It's been a long time since i've lost a plant to bugs...rot once in awhile will get one before I see it...but not very often anymore.