Just reading about this, and seeing the damage upsets me, I'd have told the guy, that he's not getting paid since the smell alone is a sign that he used a lot of chemicals when requested not to, and that, he'll be lucky if damages aren't sought in court.

I would also be cautious about eating the produce from the plants, since there's no telling the soap he used. Time and effort in tending to that garden, just for an inconsiderate person to waste, because they cared more about routine.