Noting readers’ interest in this subject [Top searches] Hilary writes:
Since the boiled rhubarb leaves were a hit perhaps we should explain how to do it?
Take a very large saucepan and put in 8 -10 rhubarb leaves cover with water and bring to boil.
Boil until the leaves go slimy about 30 mins add more water if necessary, then strain and bottle
Use 1/4 part to 1part water and spray plants
If badly infested with black fly, white fly etc use 0.5 – 1 part water.
And spray every 2 or 3 days.