I got thrips last summer, late in flower. I called the company that makes Spinosad and they told me it was OK to use until a few days before harvesting edible fruits and, on that basis, it should be OK to use on cannabis, as well.
Lo and behold, those little assholes paid a visit for my current grow, which is, now, a few days from harvest. I drenched both plants in Spinosad twice, with a week interval when I found them and it appears to have killed them off. Searching the intertubes, lady bugs feed on them so I ordered a box of them and it seems to have helped.