There are soil drench directions but I'm not sure how effective it would be as I've never used as such. I've git a bottle of neem oil if I need that.
Your plants are getting eat up because they're the healthiest vegetation in the area.
It's probably too late this season but...
Create a patch of healthy vegetation away from your main crops, be they veges or cannabis, in order to use as a trap crop for the hoppers.