I’ve read that some people on the forum use a concoction made with rhubarb leaves to cure some pest problems, aphids I think have been mentioned. Never used it myself, usually spray them off with water. Picking rhubarb today, I noticed some puckered leaves â€" looked at them closely and they are being attacked by aphids! I wonder, has anyone actually examined the aphids that have been doused in rhubarb spray to see if it actually kills them, or maybe the spray itself is just knocking them off? Food for thought?
Interesting - with blackfly on the beans, I too just use a good jet & finger & thumb!
While I am no microbiologist or chemist the active ingredient in Rhubarb leaves (Oxalic Acid) will definitely kill most things...
I prefer Tim's squirt and smear technique or just leave the ladybirds and lacewings to clear them up!
;D
Oxalic is pretty deadly; I use it to control bee mites, and it needs careful handling. if it's trickled over the frames (the way i do it) then it can damage the bees if it's repeated within the life of that generation of bees; if it's used as a vapour then a lungful could severely damage the beekeeper. It will undoubtedly kill aphids, as they're pretty vulnerable. Try boiling up some rhubarb leaves and try it; since I now have a supply of the crystals, I'll be using that if I ever need it.
Thanks for those replies - I guess that the sap in the rhubarb leaf doesn't contain much oxalic acid then, or the aphids would die when feeding! I suppose it must be locked into cells in the leaf.
I am not keen on the idea of boiling rhubarb leaves ... the vapours must be ghastly ... the method I use is to dump half a dozen leaves into a bucket of water, bash and leave to get rather stinky. Then I strain straight into a sprayer , being careful not to handle the liquid. I have used it on blackfly on beans, it doesnt kill them outright but it definitely gives them a good knocking.
You won't get any oxalic vapour from boiling; the vapourisers use either an electric element or a bottle gas flame to evaporate the crystals. Boiling is perfectly safe, and it won't do any harm to the oxalic either. A lot of organic poisons would be destroyed by it though.