Can your employer deny you paid sick leave when working harvest?

I don't think is possible because that's the whole purpose of sick hours as long as it's honestly justify, because only after the third day you are required to bring a doctor's note but you can always refer to the main office and find out .

Harvesters have no rights. More importantly all types of workers buying into the "unions are bad " propaganda from big money interests is the reason for that and for wages being so low and benefits so hard to get.