Q.Do I spray insecticide on butter beans when they bloom
We spray insecticide on string beans when they bloom to keep bugs from stinging them. Do we do the same for butter beans?

I would not spray your plants unless necessary. In the case you actually are having insects attacking your plants.
Spraying the plants could inhibit bee pollination.
If you do find spraying necessary, Neem Oil is a good choice.
Here are a few links for you.
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
https://www.gardeningknowhow.com/edible/vegetables/beans/growing-butter-beans-in-your-garden.htm