Like Andy said, those buggers can attack fruitlets very early esp. if the temp is right for them to emerge from the ground. they had wiped out all my peaches in 1-2 days.
For apply, it's better if apples can size up a bit a bit before you can bag. For me, a dime size. Before they are that size, you can either spray Triazicide at petal fall and 7 days later if pressure is high. If not, 10-14 days is suggested.
For me, I spray Surround at petal fall and a time or two more if needed. Then, I bag. Time consuming but I learn to enjoy bagging. It's me in the middle of my orchard, a Zen moment :slightly_smiling: I bagged a few hundred apples last year.
I love having perfect, pesticide free apples at the end of the season.
I don't bag pears. Most of PC scars on my pears are superficial. Pears grow fast and have dense flesh I guess.
My #1 enemy this past year is stinkbugs. With stinkbugs, even my pears sustained some damage. I'll spray Surround on pears this year a few times..