Samurai, like many insecticides, is toxic to bees. It can kill bees if they are oversprayed, exposed to spray drift or make contact with Samurai in any way.
The key to keeping bees safe is to avoid them being exposed to Samurai.
Samurai is:
Moderately dangerous to bees, but only at very high doses
Safe for bees foraging at night
Toxic to bees
A useful tool for controlling insects that compete with bees