Oh, yes, I think you do. You must be speaking of union PC- the scabs just come to work when they feel like it. At any rate, I don’t think anyone can predict when they might show up with adequate accuracy to consistently get good results with a non-persistent poison. They might be working on some nearby shadblow and move when fruit is too far along or might just come from deeper in the woods where it takes longer to warm up (pure speculation here).
If you have information based on research of specific emergence times(within a day or two) related to temps, I’d be very interested. To me, after years of dealing with PC, I agree that they tend to appear when the weather turns warm, but not necessarily on the first warm night. If they did that I think a short hot spell in late winter might wipe them out.
There is a reason commercial growers around here never used malathion for protection against PC- it just doesn’t have the staying power of Imidan or Guthion although it is safer and maybe just as lethal to them while it is active.
Homeowners probably should run with the new version of Sevin if they aren’t going organic with Surround. It has a fairly persistent pyrethroid and I’ve had good luck with pyrethroids in a rigid 2 spray schedule that is done not with first warm night but when last flowering apples lose their petals. It generally protects early flowering species and varieties even if you wait until then- that tends to be the time emergence becomes likely. It isn’t warm nights so much as when the fruit is the size they want to attack, but that tends to coincide with warm weather.