I think the most likely causes for stunted fruit development is Pollination, Temperature extremes, and Too much nitrogen. In this order.
Temperatures above 90 F constantly, or dropping below 55 F after flowering?
Pole beans in soil do poorly with fertilizers high in any one of the top three nutrients preferring 10-10-10. And in AP, we generally have more nitrogen than we can sometimes get rid of.
Can you narrow your most likely issues down?
I hope this helps.
Well, I've seen bees and pollination has never been a problem here. It has been very hot, with most days above 90, lows in the 70s. I suspected high nitrate might be the problem but I hoped you might have a magic bullet.
Big change. Lots of beans, which is likely due to cooler weather but it's possible that the plant simply wasn't old enough. Highs in N. Fla dropped from 95F or so to 80s - forecast low 67F tomorrow, which is cause for celebration.
One thing I didn't mention before is that this is all from one seed, Rattlesnake variety. I'll try to post a photo soon but this thing is really huge, compared to the same bean grown in the ground. The main truck is getting to be close to one inch in diameter and it branched off about 20 times or more, in all directions. The older parts of the plant are beginning to decline but runners are still running. I may try cutting it back when production falls.
Added bonus: A few leaf eating worms, which I pick off and drop into the fish tank - generally results in a splash. Fish love live food.