. Fig. 12.—Spray burn on apples. surface. See page 152 for fuller discussion. See also ' Sappy Bark," page 25. The apple, being naturally a hardy, long-lived tree, well repays care- ful attention to preventing this trouble. APRICOT« Bacterial Canker, Bacterial Gummosis.—It is common to see globules or masses of transparent or amber-colored gum upon the surface of the trunk, branches, twigs, or even fruit of many kinds of trees, especially those of citrus and stone fruits. This is not a symptom of any one specific disease. In the stone-fruit trees, however, especially the apricot, cherry,
. Fig. 12.—Spray burn on apples. surface. See page 152 for fuller discussion. See also ' Sappy Bark," page 25. The apple, being naturally a hardy, long-lived tree, well repays care- ful attention to preventing this trouble. APRICOT« Bacterial Canker, Bacterial Gummosis.—It is common to see globules or masses of transparent or amber-colored gum upon the surface of the trunk, branches, twigs, or even fruit of many kinds of trees, especially those of citrus and stone fruits. This is not a symptom of any one specific disease. In the stone-fruit trees, however, especially the apricot, cherry, and plum, there is in California a very widespread, definite, bacterial in- fection of the trunks and branches, due to Phytomonas cerasi, which kills or injures the trees in a manner very similar to the effect of blight on pear trees. Formerly this disease often went under the name "sour ; In the apricot tree, cankers, blister pockets, or streaks of dead, brown tis- sue develop in the bark of the trunks or branches, usually in winter and early spring. Many young trees and branches are killed in this manner. Gum usually runs out from the cankers; it is at first a sticky liquid, but hardens into a stiff, amberlike substance (see fig. 24, p. 50, under "Cherry") .Killing of buds (fig. 13),blossoms, or fruit spurs with more or less gumming may also take place in a manner somewhat similar to the 8 For further information, with descriptions and illustrations of diseases, see: Hendrickson, A. H. Apricot growing in California. California Agr. Ext. Cir. 51:1-60. 14 figs. Revised 1937.
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