Diseases of fruits and nuts Diseases of fruits and nuts diseasesoffruits120smit Year: 1941 92 California Agricultural Extension Service [ik- -1-20 collapse suddenly without showing much preliminary distress, the leaves and fruit withering in midsummer. The fungus, Armillaria mellea, at- tacks the larger roots and crown of the tree and forms its characteristic, white, felty, fan-shaped sheets of mycelium between the bark and wood. Clusters of tan-colored toadstools come up around the base of dead trees after the first fall rains. Trees succumb to the disease in gradually en- Fig. 43.—Peach
Diseases of fruits and nuts Diseases of fruits and nuts diseasesoffruits120smit Year: 1941 92 California Agricultural Extension Service [ik- -1-20 collapse suddenly without showing much preliminary distress, the leaves and fruit withering in midsummer. The fungus, Armillaria mellea, at- tacks the larger roots and crown of the tree and forms its characteristic, white, felty, fan-shaped sheets of mycelium between the bark and wood. Clusters of tan-colored toadstools come up around the base of dead trees after the first fall rains. Trees succumb to the disease in gradually en- Fig. 43.—Peach poAvdery mildew: A, on leaves; B, on fruit. larging circles in the orchard, usual]}- starting in spots where native trees once stood. No resistant root for peacli trees is available at present. Tlie best chance seems to be to double-work on a resistant myrobalan, if one is found. (See p. 144.) Soil treatment with carbon disulfide shows promise for eradicating Armillaria (p. 149). Phony Disease.—This very serious disease has thus far been confined to the southeastern United States, extending west to Texas and north to Illinois. It is not known in California. The loss in Georgia alone has been more than a million trees. Symptoms are shortened internodes, a large number of lateral twigs, and flattened, abnormally dark-green leaves, which give the appearance of compact, dense growth with luxuriant foliage. Young trees are decidedly dwarfed. The fruit is much reduced in size and quantity, highly colored but of poor flavor, and commercially worthless. After several years of the disease, the trees are usually ragged, with much dying-back of twigs and branches, but the leaves are greener than those of normal trees. The virus or causative factor is confined to the roots, and the trouble is not transmitted in buds or grafts from an affected tree. But healthy trees or scions grafted to the roots of phony trees, or root-grafted with pieces of affected roots, develop the disease. In na
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