I originally posted this on the gardening thread bit will apply here
Making some homemade pesticide with my rhubarb leaves. Boil 4 mugs of water, add 4 chopped up rhubarb leaves and simmer for half hour. Remove the leaves and allow to cool. Stir 1tsp of washing up liquid into 2.5 mugs of water and then combine with the rhubarb liquid. Plonk in a spray bottle and use on pests. Don't put it on anything you're planning to eat.