When they are epidemic you really need to spray- and before they've done too much damage. Unfortunately, the spray options aren't great and unless you have some Imidan, whatever else you use is likely to lead to a mite outbreak on your apple trees and possibly E. plums.

You probably might as well run with Sevin although products like Triazide should keep damage down to acceptable levels.

I usually used Assail for apples and E. plums and often Asana for the rest this year and it worked fine although some sites needed two sprays.

Don't assume they will be back next year- here they are unpredictable.

I used Triazide and it was not very effective. JB were all over my trees again one week later.
Then I tried trap, and they are more effective. Only a couple of JB on my trees now. I just need to empty the trap every day.

I also applied Milky Spore on my lawn and hopefully next year it will be better.

Of the OTC formulations Carbaryl (Sevin) is most effective on JB. By most effective I mean "very effective".

Thanks for the comments all, for grins I slipped a sockies on 8 fruit during the height of the infestation and all of the fruit had their sockies chewed through leading to badly damaged fruit, so much for sockies on GJB.
As to the peaches -
My Sevin lists using no more than once every 14 days and a PHI of 3 days. If my stuff was actively killing for 14 days post app. that would have covered the harvest window but the GJB flight was a little longer starting about a week prior to the 1st ripe fruit. Maybe next year spray at the 1st sign of GJBs and again 14 days later. Might have to wait a bit for the PHI to start picking but, it may not cause much crop to be lost to that. Of course, that's based on this year, next year will probably be different. Spraying only at the first sign of the buggers would at least knock some of the population down.

Having no peaches left to eat now, the damned beasts are now turning to the berries but have yet to do much damage there. Currently, the apples are of no interest to the pests. Like last year, it seems that once the peaches are done they just go elsewhere and are nowhere in sight, good riddance!!!

Though some about trapping but haven't seen any setups yet that would be manageable. Don't think I need to worry about traps luring more of the things to the trees than would otherwise be there as the peaches are already a huge magnet. Just not too sure a baited trap would be enticing enough to lure the buggers from the fruit on the tree to the trap(s).

Based on research I've seen, and from my own experience, trapping is completely ineffective. When people think it is I believe it was probably the end of their cycle anyway.

It surprises me that you are facing such a long infestation. This was the first year they actually damaged fruit here and it was only at one site, but two applications was the most needed.

Triazide should stop them from doing much feeding on the fruit and stop most of the damage to vegetation- It just doesn't knock them out on contact, but they die from eating it. Sevin kills them on contact.

Michael,

We get Green June beetles here (if that is what you are referring to). Although they don't damage anything but very very ripe fruit here, one non-chemical way they can be somewhat controlled is by netting the trees. Believe it or not, they are so fat they can't fit very easily though the nets.

When my son was younger, he used to shoot them with his BB gun when they tried to escape through the nets.

I hate the way the "buzz" you when they are disturbed. Sounds just like a very mad hornet.

Olpea:
They were definitely Green June Beetles, now that the peaches are gone, so are the adult beetles, poof, completely gone! Yes, there's nothing like reaching around to the blind side of a fruit and grabbing a handful of the buggers on a half eaten fruit and then being strafed by them on their agitated exit.

I prefer to pick the fruit pretty close to fully ripe as they get turned into nectar the same day, that was nearly impossible this year as the GJBs were already working the fruit over before they got to that stage of ripeness.

H-man: They didn't seem at all interested in vegetation fortunately. Next year I'll nail them with Sevin or Triacide depending on when they show up, the expected harvest onset and the spray material's PHI. No more Mr. Nice Guy. What's odd is that this is the 1st time in 7 years I've had such an extreme case of the insect, maybe it was a fluke or cyclical thing.

GJBs are hitting my Asian pears HARD!
Haven't looked at any of the apples, but wouldn't be surprised to find 'em there.
The late summer influx of the big yellow&brown hornets has also begun. Late-ripening apples never have a chance once those suckers get started. Any fruit that ripens later than August is toast.

Had fewer JBs the last couple of years than in the recent past. They worked on the blackberries and Chickasaw plums, but didn't damage either very much.

I actually thought you were talking about Japanese beetles- I was a bit confused about the extra letter. I also get the June beetles here lately but they haven't become a pest of fruit yet even though their populations are quite high. I will keep my eyes open.

The one problem with Sevin is it kills a lot of beneficials, but for peaches this isn't the same problem as it is for apples and E. plums where mites are a more common problem.