University of California

Phytophthora Cinnamomi and wet soil in relation to the dying-back of avocado trees


Vincent A. Wager

Author Affiliations

Vincent A. Wager was Plant Pathologist, Union of South Africa Department of Agriculture. On Commonwealth Fellowship in collaboration with the Division of Plant Pathology, University of California Citrus Experiment Station, Riverside, California, September, 1939, to June, 1940.

Publication Information

Hilgardia 14(9):517-532. DOI:10.3733/hilg.v14n09p517. August 1942.

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A dying-back or decline of avocado trees has become a serious problem to growers in some parts of southern California during the last few years.4 The trees affected are usually those that are fairly old (ten or more years of age), and the trouble may occur in isolated trees or, more commonly, in groups of trees in an orchard.

Horne (7)5 describes this decline under the various names of melanorhiza, water injury, asphyxiation, apoplexy, and collapse, and associates it with such conditions as excess water, lack of aeration, and heavy subsoils, not with any particular organisms.

Affected trees appear to lose vitality; they become sparsely foliated, fail to produce crops, and their branches begin to die back. Such trees have been seen occasionally growing in sandy soil where drainage conditions would appear to be good. But in many instances, when holes were dug alongside of these trees, an impervious subsoil was found about 2 feet below the surface.

The possibility that at times the decline of the trees is caused by too muchwater, cannot be overlooked. In one instance, a hole approximately 3 feet deep was dug in an affected orchard some 10 days after a period of continuous, fairly heavy rain in midwinter. In about 15 minutes, water began to ooze out of the sides of the hole, at a depth of about 2 feet from the surface of the ground, and to trickle to the bottom.

Literature Cited

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Wager V. 1942. Phytophthora Cinnamomi and wet soil in relation to the dying-back of avocado trees. Hilgardia 14(9):517-532. DOI:10.3733/hilg.v14n09p517
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