Sierra natural science is my preferred thrip killer, but i am an organic dirt farmer. You can go to Sierranaturalscience.com and read about it. There are lots of other thirp killer out there that is just my fave.
Thrip can hurt your crop but usually doesn't devistate it. Spider mites or as we call the borg, can ruin your crop fast. So you part of growing is getting a loupe, eye piece and get to know bugs that like cannabis. Here is the loupe I have, i have 4 of them because I can never find any. [ame]http://www.amazon.com/Jewelers-Lighted-High-Power-Eye-Loupe/dp/B00OK7AC0W/ref=sr_1_12?ie=UTF8&qid=1430873391&sr=8-12&keywords=eye+loupe[/ame]
Good luck, you can handle thrip.