The same reply I entered on the other thread.
The risk from pesticide application is the bees picking up the moisture form the spray, and the spray drifting into the hive or onto adjacent flowers.
Spray before the bees start to forage, leave enough time so any moisture can evaporate before the bees start to fly. make sure the spray is not drifting into the hive while applying it.
Or do as I do and cover the hives with a white bed sheets, place a sprinkler on top of the hives and turn it on. Do this before the bees start to fly, then spray and leave the sprinkler running till all the spray mist is dry. Then remove the sprinkler and bed sheet and allow the bees to fly. The water from the sprinkler will wash and dilute any drifting spray from entering the hive. and the bees will stay in the hive as long as they think it is raining.
If water is not close by to set up sprinklers or too many hives are involved Get them to spray in the evening when the bees have ceased flight or in the early Am before the bees start to fly. If this is not possible find out what is being sprayed and the risk to the bees to determine what need top be done. If it is toxic and the application method is harmful to the bees, give the bees water in the hive with either a in hive or hive top feeder. Screen the bees in so they can not fly. If it is a strong populous colony put a top screen on the colony but keep the lid on to protect the bees from the spray mist and block the lid up so the bees have lots of ventilation. You do not want to cook your bees by confining then in the hive with out adequate ventilation.
