Referring in the Country Gentleman to Elm-leaf beetle, and the directions apply to all leaf-eating insects, Dr. Leitner recommends spraying with London Purple and says:

"The London Purple mixture recommended, as the result of careful experiment with it, by the Entomological Division at Washington, is one-half pound of the purple, three quarts of flour, to a barrel of water (40 gallons). The flour and purple are to be thoroughly mixed while dry, and may then be washed through a large funnel having a cross-septum of fine wire gauze, set in the bung of the barrel, by gradually pouring water into it. The liquid should be applied by means of a force-pump having a proper nozzle, so that it may be distributed in a fine mist, uniformly over the foliage, but not in sufficient quantity to drench it".