The University of California Statewide IPM Program has developed a list of best management practices to protect bees from pesticides. Their list also provides various links to additional resources.
Excerpts from BMP List
Identify what species of bees are present at the site and learn the specific ways to protect them. Alkali bees, bumble bees, honey bees, leafcutter bees, and other bees vary in their biology, susceptibility to pesticides, and effectiveness in pollinating a particular crop. Methods for protecting bees and promoting pollination can differ depending on the crop and bee species.
Read labels carefully before deciding which pesticide to apply and follow the product directions. Know and comply with any applicable state and local regulations.
During prebloom, do not use an insecticide or miticide (acaricide) with a long residual time (extended-residual toxicity) or with systemic (translocated) activity. Avoid pesticides with cautions on the label that read “highly toxic to bees,” “toxic to bees,” “residual times,” or “extended residual toxicity.” Residual toxicity to bees varies greatly between pesticide products and can range from hours to a week or more.