Even if you are the owner of a farm, forest, nursery, or an enclosed space production facility (e.g. greenhouse, hoop house, high tunnel) and you or members of your immediate family do all of the work, you are a 'WPS employer' and must comply with some of the requirements.
If you bring workers on the property by any means, you are responsible for providing them with protections required by the WPS. Labor contractors can be assigned WPS responsibilities but the labor contractor is not responsible for your WPS compliance. See the “How-to-Comply” Manual Chapter 2 and Chapter 3.
If you employ handlers directly, you are responsible for providing them with the protections required by the WPS. See the “How-to-Comply” Manual Chapter 2 and Chapter 4. Commercial pesticide handler employers are responsible for providing the handlers they employ with those protections. See the “How-to-Comply” Manual Chapter 5. Information exchange is key.