Diseases of fruits and nuts Diseases of fruits and nuts diseasesoffruits120smit Year: 1941 98 California Agricultural Extension Service [Cir. 120 sionally spreads at blooming time; in extreme cases it destroys a large proportion of the blossoms. Blast of blossoms (fig. 47) is particularly bad on the Winter Nelis variety. Unlike fire blight, vhich the disease re- sembles in some respects, blast does not usually kill the twig beyond the blossom spur and does not produce bacterial exudate. Infection may take Fig. 48.—Blast of pear on twig and branch. place in the dormant season through wound
Diseases of fruits and nuts Diseases of fruits and nuts diseasesoffruits120smit Year: 1941 98 California Agricultural Extension Service [Cir. 120 sionally spreads at blooming time; in extreme cases it destroys a large proportion of the blossoms. Blast of blossoms (fig. 47) is particularly bad on the Winter Nelis variety. Unlike fire blight, vhich the disease re- sembles in some respects, blast does not usually kill the twig beyond the blossom spur and does not produce bacterial exudate. Infection may take Fig. 48.—Blast of pear on twig and branch. place in the dormant season through wounds, including those on cluster bases; sometimes cankers of considerable size (fig. 48) are produced, but they are more superficial than blight cankers. The affected bark turns light brown to tan in color and eventually sloughs off, often without killing the inner bark. Blast of pear is caused by Phytonionas syringae— essentially the same organism as that which causes blight of lilac in some places, blast of pear and apple in the eastern states, blast and black pit of citrus, and bacterial gummosis of stone fruits in California.
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