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Histological studies through lesions made in apple wood by Ceresa bubalis, the buffalo treehopper, revealed the cause of the peculiar rolling out of the wood characteristic of wounds produced by this insect. Sections were made through one, two and three year old lesions. A layer of corky tissue is formed over the wood cells that are cut by the ovipositor and exposed to the air. The two layers of corky bark adjacent to each other do not unite and this bark formation results in a wedge-shaped section of the limb being separated from the remainder. Because of this, part of the cambium layer is isolated from the rest, and is prevented from uniting with the other cambium to heal over the wound. The severed part, as well as the other cells, continues to grow and the force exerted results in the peculiar rolling of the tissue. Older lesions increase in width but there is a corresponding decrease in depth. The mechanical injury is very severe and there are evidences that decay sets in due to the wounds. While these may eventually heal over the decay has already entered the heart wood and ultimately this secondary injury may kill the entire limb.

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Proceedings of the Iowa Academy of Science





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©1922 Iowa Academy of Science, Inc.



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