Don`t let those rascals get set in. Watch the underside leafs for infestation. When you see it ( clusters of yellow eggs ), pick the whole leaf off and destroy it. Trashcan or smash the leaf underfoot on a good concrete surface. Practice the side wiping motion with the heel of your tennis shoe. They must die. It is the only way...short of pesticides which I don`t use. Inspection of your garden beans on a daily basis will help you to have a more bountiful crop.

If you have several acres of beans, I would think that you have contacts in the aerial crop dusting industry. LOL!

I think the rule of thumb on Pedio wasps is that you need a quarter acre of beans for the intervention to be worthwhile. Extreme hand picking can have much more impact than spinosad or neem. I like to wear disposable gloves annoited with a little vegetable oil, and go after them two handed. Don't see many of them these days, though. I keep about 20 percent of my space in flowers and buckwheat, and have so many naturally-occurring predators that the bean beetles never gain a foothold. Wish I could say the same for squash bugs.

MBB infestations seem to be especially up and down.

I think mad efforts at physical control are a waste of a lot of time that can spent on something else. I agree the wasp is expensive and probably only worth it for market growers, and by the time MBB is present in significant numbers it's too late.

IMO, the important thing to know is this: MBB prefers Phaseolus cultivars over other legumes by a huge degree. If one's goal is to always have a warm-weather legume crop of some kind, then do not limit it to Phaseolus. Much of north america will allow production of Vigna cultivars, for example, the asian yard-long bean is a nice substitute for green beans. If the MBB comes on strong, your Phaseolus plants will act as a trap-crop to the benefit of the other legumes.