It removes the roots from the equation lol or a good chunk of them. I just did this to one of my girls last night to try and flush some nitrogen out of my plant, but in my case I plant to harvest in 7 days. She still looks happy for as half arse as I did it I used a clean mop bucket and some white cardboard from a pizza box some stuff to push against the bottom of the plant to hold it stable and some fresh cold water. I ran 32C about 88 degrees all night at 1500 co2 ppm not even a drooped leaf but she's a little lighter in colour.. just a little. I don't mind that was my goal also I'm gonna have to be babysitting this experiment. Also I'm gonna add ice to see if it turns purple lol. I'm literally just experimenting with my strains and pushing them to the limit. So if your asking if it helps it depends on how you look at it removing most the root would clear the problem but it depends on the genetic and environment on how the plant responds.
I don't think we've even seen the above-ground parts of the plant yet. It's only week 7, OP could have a month or more left in flower...
At this point I would think either physically remove as many of the bugs as possible (by spraying and/or dunking the root ball/net pot in water or H2O2 solution) treat the roots with whatever you can that's not a harsh systemic chemical (maybe something like Botanigard 22WP although I'm not sure how effective that is in DWC), put sticky traps all around the stem to catch the flyers, and finish the plant out as best as possible, OR go nuclear and chop everything now, take clones from what you can and keep them clean, clean/sterilize all equipment and grow medium, wait a few months to make sure they're gone, and hope for the best next round.
If it's indeed root aphids, I've heard they are a real pain to get rid of. Next round I would definitely consider smaller buckets and not doing a SCROG, something that's easier to take apart and inspect the roots periodically, and easier to apply treatments if needed. Would be a real bummer to get a nice fancy setup going again, only to have them come back halfway through.
8" pipe. Yeah I've used Imidacloprid and you have to clone out three generations to be safe. I really needed/wanted those genetics
