This section is from the book "The Gardener's Monthly And Horticulturist V18", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
The cause of the plum knot - a fungus working from the outside of the bark inwardly - has been so clearly developed by Professor W. G. Farlow that there is no longer any excuse for knots in a good orchard-ist's grounds. Washes must certainly destroy them. We fancy that no tree annually whitewashed would suffer from plum knot. Of course one may put clay or soot into the whitewash to destroy the glaring white.