Some mosaic diseases ofPrunusspecies

Abstract

Abstract does not appear. First page follows. In the absence of a visible fungus or bacterial pathogene, the diagnosis of a plant disease depends in a large measure upon the recognition of symptoms. This observation is particularly applicable in the study of diseases of deciduous fruit trees in California where there is found a relatively greater proportion of virus and nontransmissible diseases than is the case in more humid areas. It has seemed desirable, therefore, to assemble and to study, under comparable conditions, some of the prevalent virus diseases of deciduous fruit trees and to improve the criteria for distinguishing these from nontransmissible diseases such as exanthema and little-leaf, or rosette, the latter of which may cause symptoms on grape leaves strongly suggestive of a mosaic disease. It is a rather remarkable fact that none of the several well-known virus diseases of stone fruits in eastern United States, namely, peach yellows, peach rosette, little peach, and phony peach, have been found in California. On the other hand, there are a considerable number of virus diseases of these plants in California, few or none of which seem to be established in the eastern states. Among the latter group, only cherry buckskin (8)4 and peach mosaic (3), (6) have been studied in any detail. The earlier plan of this work, begun in 1932, involved the collection of those virus-type diseases that were found on deciduous fruit trees from which the more important were to be selected for further study.