Buy some food grade de earth, let your soil dry and keep it dry for 72 hours, it's powder so sprinkle around plant and lightly dust fans use a piece of balled up toilet paper and dust both sides, after 72 hours give a light flush and check ph, that will kill them off, ure outside? Bring them in at night so they dont get wet during treatment, i use it all the time indoors for those gnats or fruit flys that sometimes get in your mix, even killed off a bad case of thrips that somehow infected my grow, it will kill any bug with an exoskeleton pronto and organicley and cheaply, the key is not to let the dust get wet during treatment.