They have a different type of Pesticide Applicator License that must be constantly updated by attending training meetings. My talk centered on helping the attendees communicate to homeowners how to properly water lawns. About everyone has seen residential sprinkler systems running every day and during rainstorms. I suggested the professionals first tell the homeowners the proper way to water the lawn and then point out the threat to groundwater by overwatering. Even homeowners agree that keeping groundwater clean is a good idea, and they tend to listen when you explain what they do affects everyone's water.
Water quality is everyone's responsibility.
In the past, farmers were the leaders in protecting groundwater. Now, they can count on ground and lawn care professionals to help in the fight. If we can convince homeowners to use pesticides carefully and water properly, then everyone wins, and the prize is clean water. Thoroughly but infrequently. When the soil is dry to a depth of 5 inches, water long enough to rewet the soil to a depth of 5 inches.