Would it be at all feasible to smoke out / suffocate bugs? Put a garbage bag over the plant, and a small controlled flame (DANGER WILL ROBINSON, DANGER, do not attempt unless you're familiar with what fire does to things when it goes wrong) like a candle in the dirt?
Suck all the oxygen out, fill it up with smoke-type gases, bugs become dead. Plants don't exactly have a hyperactive metabolism, so I assume they'd survive longer than the bugs without oxygen (No light = no replacing oxygen themselves, right?)
Any thoughts?