. Diseases of economic plants. Plant diseases. Poraaceous Fruits 65 With the flow of sap in the spring these infested hmbs exude a milky fluid teeming with the bacteria and thus be- come centers of reproduction. It has been demonstrated that several species of insects can carry infection, but it is not probable that they are really important agents of transmis- sion/^ Two additional forms of this disease, according to the part affected, are recognized: (1) blossom-blight, (2) body- blight and canker. Neither of these differs essentially from twig-blight, though body-blight or canker is especia
. Diseases of economic plants. Plant diseases. Poraaceous Fruits 65 With the flow of sap in the spring these infested hmbs exude a milky fluid teeming with the bacteria and thus be- come centers of reproduction. It has been demonstrated that several species of insects can carry infection, but it is not probable that they are really important agents of transmis- sion/^ Two additional forms of this disease, according to the part affected, are recognized: (1) blossom-blight, (2) body- blight and canker. Neither of these differs essentially from twig-blight, though body-blight or canker is especially worthy of men- tion on account of its pecul- iar destructiveness. This form occurs where infection is led by a spur, shoot, or sucker, or where the germ enters through a wound into the body or main limbs of the tree. The result is a canker more or less cir- cular, which may even girdle the tree or branch, and which in any event causes serious injury. The susceptibility of the tree is largely influenced by ex- ternal conditions. In general, anything that leads to rapid growth, resulting in tender shoots, favors the development of the disease. There is also much difference in resistance offered by different varieties. The Anjou, Kieffer, An- gouleme, and Seckel possess more resistance than the Bartlett, Clapp, or Flemish Beauty. Based on the facts as stated above, the following sugges tions for avoiding the blight were deduced, and tested b\ Waite. 1. Pruning in winter when the tree is dormant promotes growth and favors blight. Withholding the pruning knife, which may not otherwise be best for the tree, will reduce this Fig. 31. — Fire-blight showing exu- date from bark, much enlarged. This teems with the causal bac- teria. After Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Steven
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishernewyo, bookyear1921
