Eddy, how much you need to spray for PC has a lot to do with where you're located. In the northeast only 2 Imidan sprays are generally needed- 1 at petal fall, the 2nd 10 to 14 days later. Sevin is easier for the homeorchardist to find and should be used on a tighter schedule and sprayed 3 times for adequate control. I have heard of others using Malathion affectively. Still others get adequate control organically with Surround.
[NAFEX] spraying curculiio,
Alan Haigh, 02/08/2009