I have killed them using
Trifecta but it is expensive. So, now I make my own from essential oils (the exact ones on the label). However, then I add some brewed habenero pepper oil to the final mix. It takes persistence though. Once I see the larvae I blast em every 3 days. The nice thing about
trifecta and plant oils is you can safely use them anytime even in flower. However, if you try the pepper oil they may need rinsing before harvest and I always wonder if that is hard on the trichs.
Now I do preventative sprays with a
trifecta based spray and then I don't have to spray in flower.
If your in soil or maybe even coco you might try diatomacious earth (food grade). It cuts up the little bastards and they die as they crawl through it (like microscopic shards of glass). However, you have to reapply to the top of the media after watering. It is cheap on Amazon by the 10lb bag....lasts forever. Just make a squeeze bottle or use and old baby powder container to dust the tops of the containers and any surfaces you might suspect they are crawling around on.
D