Maybe the hot weather is making the flowers slightly wilt so the bees can’t physically get inside??? I know that sometimes they’ll bite the back of the flower to get at the pollen/nectar and thus not actually pollinate it so the bean doesn’t set.
I seem to have a distant memory of some advice from years ago of drenching the plant in slight sugar solution to encourage bees to pollinate. I’ve not tried it, and quite why this would work over and above keeping them well watered I’m not sure. To my mind it might encourage ants, but could be worth a try on one of them.
Jan
