No I've never used it but will be really interested to hear how it goes.
I used to know a gentleman who made rhubarb leaf tea to rid his plants of aphids.
Fo info (might try this one as well)
Rhubarb (Rheum rhaponticum).
Perennial potager plant.
Active ingredients. Oxalic acid as salt of calcium.
Action. Insectifuge against aphids, caterpillars, and other larvae. Repulsive to herbivores.
Preparation. In cold maceration, use 1 lb. of chopped leaves in 3 quarts of water; allow to soak 24 hours before filtering. Use full strength. This is a great way to use rhubarb leaves as you eat the stalks.
Thanks to wivvles for the link in an earlier thread - I am going to try and make very good use of it.