We had a bad outbreak of Japanese beetles last year and I swore I would put down milky spore to try to get ahead of them. Of course I did not do that. So, this year the JBs are even worse. I have four traps out and have been emptying the bags for re-use. I must have collected a few gallons of JBs so far. I'm using the traps with the hour-glass shaped plastic bags made by Spectracide. Sometimes the bags have been full all the way to the bottom of the plastic holder. Two of those fills a plastic grocery sack, which I then knot and throw in the trash. Trash is getting REALLY stinky.
I had one of the plastic holders from last year, but no extra bait, so I put some cloves in a baggie and smashed them a bit, which also made small holes in the baggie. That works as an attractant because the main ingredient in the bait is eugenol, which is the principal essential oil of cloves. It isn't as effective as the commercial bait, but it does work.
Yesterday I bought a 20lb bag of the spreadable milky spore and will spread it this week. I'm hoping we will get rain in a couple of days, and my plan is to spread it the evening before a rain if possible. Where I will spread it is too far from my water and I think you are supposed to water it in after spreading. Anyway, I'll be treating this week and again in the fall, and then again in the spring. Hopefully that will help. Anyone know of a use for several pounds of dead Japanese beetles?