Autumn sowing of Beans and Peas

Does anyone have any ideas on stopping short tongued bees robbing the nectar from my broad beans without pollinating them?

I sometimes have to use a net against carpenter bees who bite through the base of the flowers. The problem has improved now there are other flowers for them to feed on- a good excuse for leaving the early dandelions!

If you net them, are other insects trapped in the nets or how do they then get pollinated?

It is quite a wide mesh ( originally part of a fruit cage) so smaller insects can get in and out. The carpenter bee is pretty big!