I've never used this on 'tunias, but I've used it on lots of other plants - try it on one stem first: 50:50 mix of 70% isopropyl (rubbing) alcohol:water with about 6 drops of dishsoap per quart. Soak leaves and stems, paying particular attention to undersides. This remedy has no residual effects, so you'll need to remain vigilant and treat at least once/week. If I was you, I would obtain some cold pressed neem oil and add it to the mix. Neem works slowly (takes 1-2 weeks to see full benefit of results), but is wonderful as an anti-feedant and a sterilizer (inhibits the metamorphic cycle) and is extremely safe.

Al