Are these a threat to my weed plant

Looks like a leaf hopper not an aphid. They feed on grasses and the juice from the leaves. Should not be a big issue, if you notice their numbers increasing and the plants not looking so hot, then treat em. Till then I would just ignore it. they don't pick on cannabis plants normally from my experience with them but that could be an inaccurate observation. Thrips cause similar damage and how they eat and feed, and they love cannabis plants. I used a bio contoral this year outdoors. Predatory mites and they worked well. no massive thrip issues and normally they wreck my tomatoes and cannabis prety good.