Prevention of disease.
In forest trees.—The prevention of diseases in forest trees is more or less difficult. The best method of keeping a tree healthy is to remove those conditions which favor disease. Trees should be grown in well-drained, carefully prepared soil, free from previous fungous contamination. Seed-beds in which a disease has started should be sprayed with Bordeaux mixture. Trees that become dis eased because of the attack of fungi on their leaves or younger branches should likewise be sprayed with various fungicides, notably Bordeaux mixture; this will prevent all mildews and blights, to a greater or less degree. For fungi that attack the heart-wood, careful attention to wounds is advisable. Wherever a branch is broken or sawed off, the exposed surface, wherever practicable, should be coated with some antiseptic substance, preferably coal-tar creosote that has been heated. All wounds should be carefully trimmed, so as to facilitate the healing process. In large forest tracts measures of this kind may not yet be prac ticable, and in such cases the only preventive measure is to destroy the source of infection, as far as pos sible. On limited areas it is possible to remove the punks or fruiting bodies of the wood destroying fungi and, better still, to cut down all trees which show any signs of being dis eased. A careful weed ing out of diseased trees will remove the source of infection for the other trees, to a very large extent.
Is hewn timber.—The decay of cut wood may be retarded or pre vented by various means. The easiest way to prevent the develop ment of the fungi is to "treat" all wood which is exposed to atmos pheric agencies. Charring will frequently be found useful. For getting longer service out of wood, it should be chemically treated by painting with some preservative, such as carbolineum or coal-tar creo sote. Care should be taken, however, that only absolutely dry wood is painted. Timber immersed in a solution of one part of corrosive sublimate to 150 parts of water will be proof against the attack of decay-producing fungi for many years. The best
preservative is undoubtedly coal-tar creosote, which can either be painted on the wood or be pressed into it by various mechanical devices.
Literature.
The following are some of the more important books and papers relating to the diseases of American trees and timber : G. F. Atkinson, Studies of Some Shade Tree and Timber Destroying Fungi, Cornell Agricultural Experiment Station, Bulletin No. 193 (1901); E. M. Freeman, Minnesota Plant Diseases, Chapters on Diseases of Timber Trees (1905); Galloway and Woods, Diseases of Shade and Ornamental Trees, United States Department of Agriculture, Yearbook 1896, p. 237; Robert Hartig, Diseases of Trees (1894); F. D. Heald, A Disease of Cottonwood, Nebraska Agricultural Ex periment Station, Bul letin No. 19 (1906); Perley Spaulding, A Disease of Black Oaks, Report Missouri Bo tanical Garden (1905); the following by Her mann von Schrenk: A Disease of Taxodium, and of Libocedrus, Re port Missouri Botan ical Garden, No. 11 (1899); A Dis ease of the Black Locust, Report Mis souri Botan ical Garden,, No. 12 (1901);" The Bluing and Red Rot of the Western Yellow Pine, .Bu reau of Plant In dustry, Bulletin No. 3G (1903); Dis eases of New Eng land Coniferous Trees, Division of Vegetable Physiol ogy and Pathology, United States De partment of Agriculture, Bulletin No. 25; Fungous Diseases of Forest Trees, United States Department of Agriculture, Yearbook, 1900; Two Diseases of Red Cedar, Division of Vegetable Physiology and Pathology, United States Department of Agricul ture, Bulletin No. 21; A Disease of White Ash, Bureau of Plant Industry, Bulletin No. 32 (1903); Decay of Timber, Bureau of Plant Industry, Bulle tin No. 14; Diseases of the Hardy Catalpa, Bureau of Forestry, Bulletin No. 37; Diseases of the Redwood, Bureau of Forestry, Bulletin No. 33; Seasoning of Timber, Bureau of Forestry, Bul letin No. 41 ; C. S. Sargent, Silva of North America (has numerous notes on fungous and insect diseases of trees); C. Freiherr von Tubeuf, Diseases of Plants, Longmans, Green & Co., New York (1897).