With every post like this, you will get loads of don't use them
at all. Good advice, but early in the season I use sevin, which
is deadly to bees, to kill cucumber beetles. If I did not, I
would lose most of my plants.
So, if you are going to use pesticide around bees do not use
powders. Bees will pick it up like pollen and carry it back, if
they make it, to the hive which results in more bees killed, and
maybe even the queen. Encapsulated powders are even worse, since
they are about the size of pollen.
In order of least harmful to most- oil or water based sprays,
wettable powder, powder, encapsulated powder. If you use
rotenone, do not use it as a powder but mix it with water and
spray.
Spray in the evening after the bees have stopped flying. Avoid
flowers but aim at foliage. Avoid drift to flowering plants- even
weeds- in the area. Spray when the weather is warm, because the
pesticide breaks down faster with temperature.

Bill T
Bath, ME