Powdery, mites, botrytis....I have no problem. Root Aphids are the worst; they sneak up on you and ruin your garden. I have had these little fuckers pop up every year or so. Typically some sort of new cloned genetic or cross contamination from a harvested pot/plumbing gets into a freshly flipped pot. I grow hydroponic SOG with felt pots 9 roots per light and Deep Water SCROGwith 4 per light.
One Solution that has been used/recommended that should never be used:
Bayer 3 in 1 used 30 days from harvest: Imidacloprid, Tau-Flavalinate, and Tebucanazole are the active ingredients. Imadicloprid is a synthetic nicotine product and is systemic. It is toxic to mammals, fish, and insects. It is nasty stuff. It is debatable whether it is safe to use on anything other than mothers a generation removed from anything that will be smoked. Tau-Flavalinate is a synthetic pyrethroid and kills SOME aphids on contact. Tebucanazole should never be used on anything that is going to be smoked.
Things you can use that will kill some aphids, but will inevitably leave a resistant population that will re-infect your garden are Neem Oil Extracts, Pytheum products, and other oils (cinnamon, etc.). The aphid life cycle is multi-stage and these products leave a percentage of bugs every time. The next time the population takes off, you're fucked.
GoGnats will slow things down, but the aphids will still fuck your plants.
The only way I have found to save your genetics and not risk poisoning someone is too kill everything except your mothers, use a .0015% imidacloprid ONLY drench/dip/flush on the moms(Bayer Fruit, Citrus, and Vegetables(.235%) or Ortho Max(1.47%) dilute appropriately.) I will let everything dry out as much as possible before the application to ensure that the imidacloprid is absorbed into the media/root ball. If I'm flushing a deepwater system, I only run it for 10 hours during the light cycle and the flush the system.The mom is inoculated, and I have never had problems with any imidacloprid treated plants again.
Sorry there isn't a better solution. I wish I knew the safe interval between treatment and harvest for cannabis using imidacloprid. If I was confident it was safe, I would use it in veg as part of the standard regimen.