Pomological Studies of Apple Trees

Report on some of the Diseases and Insects Affecting Fruit Trees and Vines.
by THADDEUS WILLIAM HARRIS
Professor of Entomology of the Mass, Horticultural Society.

(From the Proceedings of the American Pomological Society, we copy below Dr. Harris' valuable treatise upon the various insects that infest fruit trees, alluded to in our last, and although only few of these have yet appeared in California, we believe we can do a great service to our orchardists by presenting this invaluable document entire, and thus lay before them a treatise for future use, for in all probability we shall find them in coming years among the trials we shall have to contend against:)

SWOLLEN BRANCHES OF THE APPLE TREE. On the 31st of May. the Hon. M. P. Wilder sent to me some pieces of the limbs of an apple tree, which were singularly enlarged in diameter to the extent of several inches. He found the disease to prevail on the north side of the tree, white the south side was almost entirely free from it The specimens were carefully examined by Prof. Asa Gray and myself, without insects, their punctures, or their tracks being found therein.

 One of the branches, measuring two and a-half inches in circumference, and the enlarged portion was eleven inches in length. The outer bark seemed perfectly healthy. When sawn transversely, the pith was not found in the centre of the piece, but nearer to one side than the other, where the layers of wood are thicker, and looser in texture. It was also evident that the thicker layers followed a Spiral direction around the limb.

When the bark was raised, the wood presented a singularly irregular surface, caused by numerous depressions and furrows, which were filled by corresponding elevations of the inner bark. The disease was evidently a diseased formation and irregular deposit of woody matter. It belongs to the province of the vegetable physiologist to explain the cause of this preternatural and diseased formation.

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Reading this I got to wondering what they meant..."swollen" branches. I mention this as I raise many types of apple trees, crabapple, MacIntosh and some straight modern types that are hybrids. I had to think about this for a bit and nothing came up, so I thought perhaps I could find something out there that would be similar.


I think they horticulturists of Massachusetts are discussing Sooty Blotch which does cause surface blemishes that detract from fruit appearance and lower fruit quality and market value. Sooty blotch also shortens fruit storage life because of increased water loss. Sooty blotch is a disease complex caused by several unrelated fungi. See tje above picture which is on a blackberry (a member of the apple family)

Symptoms

Sooty blotch appears on fruit surfaces as sooty or cloudy blotches with indefinite borders. These blotches are olive green to black and can be removed by rubbing vigorously and happens during overwintering because the trees are too close to each other and were not pruned back vigorously enough in the fall.

Branches touching each other catches things that the wind brings in, instead of just flying through or landing briefly.

The UPENN Site mentions that Disease outbreaks are favored by extended periods of above-normal summer temperatures, combined with frequent rainfall and high humidity. These diseases usually appear on fruit late in the season and of course recommends thinning

The writer says that in the next issue of the CA Farmer we will learn more.  IN the meantime this is my guess...any other takers?