when I had a greenhouse , it got an attack of greenfly and all sorts of aphids . I got some yellow card and smeared vaseline all over it , and held it just above the beasties and tapped the plant . It caught millions of the little buggers. I also left a few cards made up the same , near to the plants . These too caught loads of them , and the problem mostly went away . There were still some left, but most had gone . Maybe worth a try ...?
cheers
Russ