AGRICULTURAL EXPERIMENT STATION EXPERIMENTING STAFF ALBERT R. MANN, B.S.A., A. M., Acting Director. JOHN L. STONE, B.Agr., Farm Practice. JAMES E. RICE, B.S.A., Poultry Husbandry. GEORGE W. CAVANAUGH, B.S., Agricultural Chemistry. ELMER O. FIPPIN, B.S.A., Soil Technology. G. F. WARREN, Ph.D., Farm Management. WILLIAM A. STOCKING, JR., M.S.A., Dairy Industry. WILFORD M. WILSON, M.D., Meteorology. RALPH S. HOSMER, B.A.S., M.F., Forestry. JAMES G. NEEDHAM, Ph.D., Entomology and Limnology. HARRY H. LOVE, Ph.D., Plant Breeding. ARTHUR W. GILBERT, Ph.D., Plant Breeding. EDWARD G. MONTGOMERY, M.A., Farm Crops. WILLIAM A. RILEY, Ph.D., Entomology. MERRITT W. HARPER, M.S., Animal Husbandry. JAMES A. BIZZELL, Ph.D., Soil Technology. GLENN W. HERRICK, B.S.A., Economic Entomology. CYRUS R. CROSBY, A.B., Entomology. HAROLD E. ROSS, M.S.A., Dairy Industry. KARL MCK. WIEGAND, Ph.D., Botany. EDWARD A. WHITE, B.S., Floriculture. WILLIAM H. CHANDLER, Ph.D., Pomology. ELMER S. SAVAGE, M.S.A., Ph.D., Animal Husbandry. LEWIS KNUDSON, Ph.D., Plant Physiology. KENNETH C. LIVERMORE, Ph.D., Farm Management. ALVIN C. BEAL, Ph.D., Floriculture. MORTIER F. BARRUS, Ph.D., Plant Pathology. CLYDE H. MYERS, M.S., Ph.D., Plant Breeding. GEORGE W. TAILBY, JR., B.S.A., Superintendent of Livestock. PAUL WORK, B.S., A.B., Vegetable Gardening. FRANK E. RICE, Ph.D., Agricultural Chemistry. VERN B. STEWART, Ph.D., Plant Pathology. IVAN C. JAGGER, M.S. in Agr., Plant Pathology (In cooperation with Rochester University). DANIEL S. FOX, B.S., Farm Management. WILLIAM I. MYERS, B.S., Farm Management. LEW E. HARVEY, B.S., Farm Management. LEONARD A. MAYNARD, A.B., Ph.D., Animal Husbandry. LOUIS M. MASSEY, A.B., Plant Pathology. BRISTOW ADAMS, B.A., Editor. LELA G. GROSS, Assistant Editor. The regular bulletins of the Station are sent free on request to residents of New York State. BLACK ROT, LEAF SPOT, AND CANKER OF POMACEOUS FRUITS1 L. R. HESLER HOST CONSIDERATIONS PLANTS CONCERNED The black rot, leaf spot, and canker of pomaceous fruits is primarily a disease of the apple, Pyrus Malus L. It affects other trees also, however, especially the pear (Pyrus communis L.), the quince (Cydonia vulgaris Pers.), and the crab (Pyrus coronaria L.), showing on these hosts symptoms similar to those on the apple. In addition the pathogene infests the dead parts of a great variety of other trees and shrubs, but in such cases there is usually no evidence that it has been the causal factor in the death of the tissues. In the State of New York, at least, this disease is of economic importance only on apple trees. VARIETAL SUSCEPTIBILITY OF FRUIT TO BLACK ROT The summer varieties of apples are affected by black rot at the time of ripening, while winter varieties commonly suffer in storage. In Connecticut black rot is a most troublesome storage rot (Clinton, 1915:5).2 OF FOLIAGE TO LEAF SPOT Brooks and DeMeritt (1912: 183), in New Hampshire, note striking differences in the varietal resistance of apple seedlings to leaf spot. In Virginia, Ben Davis and Black Twig are more severely attacked than are other varieties (Reed, Cooley, and Rogers, 1912: 5). Salmon (1907), writing from England, states that among the varieties most affected there are Peasgood, Nonsuch, Cox's Orange, and others. The writer has noted that Chenango, Baldwin, Rhode Island, and Twenty Ounce show spotted foliage more commonly in New York than do other varieties. OF LIMBS TO CANKER Varieties of apples exhibit a marked difference in susceptibility to the disease, and this variation is not the same with respect to the different parts affected. In western New York Twenty Ounce is the variety most severely affected by the canker. This variety is rarely found unaffected by canker, even in orchards that are managed according to improved methods. Neglected trees of the Twenty Ounce variety are often killed. 1 Also presented to the Faculty of the Graduate School of Cornell University, May, 1914, as a major thesis in partial fulfillment of the requirements for the degree of doctor of philosophy. Dates in parenthesis refer to bibliography, page 230. Paddock (1899 b: 181) says that certain growers in New York State have noted that Twenty Ounce is most likely to be attacked. He lists other varieties in order of their susceptibility, as follows: Baldwin, Wagener, Rhode Island, Tompkins King. Regarding the Esopus, Paddock (1899 b: 180) says that this variety has apparently run out because of this disease. In Ontario, Ben Davis, Northern Spy, and other varieties are severely injured by the disease (McCready, 1910). THE DISEASE NAMES The disease on the fruit is called black rot, ring rot, blossom-end rot, and brown rot. The first name is descriptive and definite, and seems desirable. Lesions on the foliage are termed leaf spot, brown spot, and frog-eye. The names apple canker, black rot canker, and New York apple tree canker, are most commonly applied to the disease when it occurs on the bark. The term apple canker needs some qualification, since many kinds of cankers occur on the apple. It was under such an exigency that Paddock (1899 b: 180, footnote) first used the name New York apple tree canker. The writer prefers to use this name regardless of its length, not alone because of priority, but also because of general usage. THE BLACK ROT OF THE FRUIT HISTORY The disease on the fruit was observed by Peck (1879:20) in Schoharie County, New York, and he quotes the remark of stagecoach passengers that they "never before knew of apples rotting on the tree." Arthur (1885) records black rot of quince fruit at Geneva, New York, and notes the importance and infectious nature of the disease. Scribner (1890) notes the disease in New Jersey and describes the symptoms and causal nature. The same year Baccarini (1890), in Italy, observed the rotting of otherwise sound apples, pears, and peaches, the decay occurring in a storeroom of fruit gathered when ripe; this was a new appearance of the disease in that country. Two years later Halsted (1892) discussed the black rot of quince in New Jersey. Sturgis (1893, a and b) notes the disease on quinces in Connecticut in August, 1892, and later (1894) confirms the work of Halsted. Kinney (1895 c) figures and describes the disease in Rhode Island. In the same year it became an object of control measures in Kentucky (Garman, 1895). Black rot of apple is reported by Burrill and Blair (1901) in Illinois; they give a careful description of the disease and distinguish it from other apple rots. The following year Clinton (1902), writing from the same station, remarks that the disease on |