CANKER ON PLUM TREES.
Lansingburg, April 5, 1820.
S. Southwick, Esq.
Sir—I observe in your Plough Boy of the 1st inst. some observations on the disease in Plum Trees, called Canker, wherein the writer states that the disease is probably caused by the trees being bark-bound. I have had sufficient proof to convince me that it is caused by insects only. From a variety of observations and experiments, I find that when young shoots are throwing out of the trees, they are stung by a species of fly, and a number of eggs or nits are deposited through the tender bark, where they remain until the tree commences growing the next season; those places then begin to swell, and after a few weeks, small worms can be distinctly observed by the naked eye, which, after about one month more is elapsed, eat out of the protuberances, then become black, take to themselves wings, and commence operations as before stated.
The only remedy that I can discover, is to cut off every limb affected, on its first appearance; and if the tree be so much affected as to be past cure, it should be totally cut down, in order to destroy the whole race of insects which cause the disease. The first discovery of this complaint was on the sea-board: and it has advanced north about twenty miles a year. At present nearly all the bearing trees on the sea coast to the southeast, are totally destroyed, and it pervades all this part of the country. The poorest natural blue plums are first attacked—the dark coloured grafts, next—and lastly, the light coloured fruit fall victims. Some few kinds as yet withstand their attacks. By observing the above caution, my trees are entirely free from them, and bear abundantly. I am, Sir,
Yours, &c.
ARBOREUM.