I've seen those before and I believe it's a type of moth caterpillar. Anyway, caterpillars love to eat whatever you find them on. For insects of all types the best insecticide I have found is called "Garden Safe Fruit & Vegetable Insect Killer" and it's made by Schultz. It's pyrethrin based and can be used up to the day of garden vegetable harvest. After battling a fungus gnat infestation for 6 weeks and using neem oil with poor results, I had excellent results with Garden Safe. If it can be used on vegetables up to the day they are picked (and eaten) I think it's save to use on MJ. Don't get wild with it and hose everything down, a little goes a long way. You don't want to saturate the leaves or buds but rather mist them and avoid any droplets forming on the leaves. Pyrethrin is deadly to insects so not much is needed. ------- Hope this helps!-------- Party on Dude!