Talk to them first about identifying problems and pests before using chemicals. They may not need to use as much chemical as they intend.
Then talk to them about timing spraying to reduce potential damage to pollinators (bees, especially, in your case). Spraying shortly after sundown can reduce the impact on honey bees. Spraying fruit trees after bloom will cause less damage to bees (no flowers, no bees around). Remember that they need pollination to produce their fruit crops, so protecting bees is in their best interests, too.
And then ask them to notify you before spraying if possible. You can confine bees temporarily to avoid the worst effects of spray if you know before the chemical is sprayed.