. Diseases of fruits and nuts. Fruit; Nuts. 128 California Agricultithal Extension Service [Cir. 120 l)y 110 means blight-free since in some sejisons there are pei'iocls of sum- mer humidity when tlie disease develops abundantly. In regard to other qualities, also, no entirely satisfactory late-starting variety has thus far been found, especially for southern California. It is significant that the more recent walnut plantings in that part of the state have been almost exclusively of an early-maturing, blight-susceptible variety. Meantime, the need is as great as ever for a high-producing, high
. Diseases of fruits and nuts. Fruit; Nuts. 128 California Agricultithal Extension Service [Cir. 120 l)y 110 means blight-free since in some sejisons there are pei'iocls of sum- mer humidity when tlie disease develops abundantly. In regard to other qualities, also, no entirely satisfactory late-starting variety has thus far been found, especially for southern California. It is significant that the more recent walnut plantings in that part of the state have been almost exclusively of an early-maturing, blight-susceptible variety. Meantime, the need is as great as ever for a high-producing, high-quality, really blight-resistant Fig. 70.—Full-grown walnuts ruined by blight. Chlorosis.—The foliage of affected trees is of a bright-yellow color and the growth more or less stunted and deformed. Typical chlorosis is caused in trees of many kinds by the presence in the soil of excessive amounts of lime, which prevents the normal functioning of iron in the tree. The walnut is a lime-loving plant, but in some districts where the lime content of the soil is very great, the foliage of walnut trees shows the same yellow color as that of pears and other species. For treatment see page 135. Crown Gall.—The walnut, including all the species used for root- stocks is rather susceptible to this common bacterial disease, caused by Phytomonas tumefaciens. Large rough swellings develop on the roots, at the crown, and at places higher up on the tree, esi")ecially at the point of grafting on top-worked trees. Rough, slow-healhig graft unions and points of injury are most likely to become Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smith, Ralph E. (Ralph Eliot), 1874-1953. Berkeley, Calif. : The College of Agriculture, University of California
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