University of California

Symptomatic and etiologic relations of the canker and the blossom blast of Pyrus and the bacterial canker of Prunus


Edward E. Wilson

Author Affiliations

Edward E. Wilson was Assistant Plant Pathologist in the Experiment Station.

Publication Information

Hilgardia 10(8):213-240. DOI:10.3733/hilg.v10n08p213. November 1936.

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In 1931 a heretofore undescribed bacterial canker of pear trees was found in Sierra Nevada foothill orchards. A brief discussion of symptoms, giving results of inoculations and comparing the disease with fire blight, Erwinia amylovora (Burrill) Bergey et al., was published in 1934.(18)3 The causal organism was not described except as it differed from Erwinia amylovora in producing a greenish pigment on many media, thus allying itself with Phytomonas cerasi (Griffin) Bergey et al., cause of the stone-fruit bacterial canker.(17)

A blossom blast of pear in California differing from that caused by fire blight was briefly described by Thomas and Ark,(15)4 who report the causal organism as similar to those of citrus blast and stone-fruit canker.

The orchards in which the writer first found the limb-canker disease have remained free of blossom blast, though planted with Beurre Bosc, a variety elsewhere susceptible to blossom infection. Limb and blossom symptoms in the trees growing in other districts indicate that all are phases of the same disease. One purpose of this work, therefore, was to compare the bacteria obtained from these parts of the host.

Reports from New York(3),(4) and Arkansas(9),(10) regarding infection of pear leaves, fruit, and blossoms by bacteria possessing cultural characteristics similar to these organisms were additional reasons for the study.

Literature Cited

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[15] Thomas H. Earl, Ark P. A. Fire blight of pears and related plants. California Agr. Exp. Sta. Bul. 1934. 586:1-43.

[16] Wilson E. E. A comparison of Pseudomonas prunicola with a canker-producing bacterium of stone-fruit trees in California. Phytopathology. 1931. 21:1153-1161.

[17] Wilson E. E. Bacterial canker of stone-fruit trees in California. Hilgardia. 1933. 8(3):83-123. DOI: 10.3733/hilg.v08n03p083 [CrossRef]

[18] Wilson E. E. A bacterial canker of pear trees new to California. Phytopathology. 1934. 24:534-537.

[19] Wilson E. E. Variability of Pseudomonas cerasi in physical characteristics of growth on solid media. Phytopathology. 1934. 24:548-550.

[20] Wormald H. Bacterial diseases of stone-fruit trees in Britain II. Bacterial shoot wilt of plum trees. Ann. Appl. Biol. 1930. 17:725-744. DOI: 10.1111/j.1744-7348.1930.tb07242.x [CrossRef]

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Wilson E. 1936. Symptomatic and etiologic relations of the canker and the blossom blast of Pyrus and the bacterial canker of Prunus. Hilgardia 10(8):213-240. DOI:10.3733/hilg.v10n08p213
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