This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
It has been charged to insects, but my microscope, (which is the kind called a "cloth prover,") and is of one inch focal distance, detects none There are insects seen in the later stages of the evil, among the convolutions of the leaves, but they evidently came there as they seek out other decaying vegetable or animal matter, to find food and a home; and were no how the cause of the curl.
One thing is obvious to slight observation, that is, that the evil arises from within the bud or tree itself since the moment the leaves begin to expand, they are seen in many cases to be taking on a sickly state. It should not be forgotten, too, that all this takes place at an earlier period than insects show themselves to any extent.
The disease, for such I certainly consider it, is obviously the result of severe and untimely weather, and admits of a ready and satisfactory explanation. Its history, in connection with the state of the weather, during the last spring, will, I think, set this matter in a clear light, and will show, moreover, that the peach suffers this liability to disease in common with most tropical and semi-tropical trees and plants, and is closely allied to -one, (the most common) form of the potato disease.
From March 22d to April 1st, inclusive, the weather was very unusually warm, the thermometer standing on the 30th at 75°. The gooseberry was rapidly coming into leaf, and the cherry and the peach were almost bursting into flower. I said to my family at this time, " these trees must suffer. They cannot flower safely now, nor yet be safely retained in their swollen state until the ordinary time of flowering," which is here usually between the 10th and 15th of May.
On the 2d of April commenced a season of cold and damp weather, (occasionally exhibiting both frost and snow,) which continued exactly thirty-six days, i. e., until 8th of May. On that day began a season of warm, impulsive weather, which brought the peach into full bloom upon the 13th, i. e., in five days. Those buds that had been most excited late in March, never opened. On examination they exhibited the elementary parts of the flower in a dry and friable condition. The flowers which opened, exhibited various degrees of health. A few of them set fruit, but the most of them blasted. The same general course was run by the leaf bads. A few whole trees, and many single branches on others, never fully expanded the leaf buds, but died in the effort. A few trees were scarcely affected at all. Between these two extremes was every degree of suffering by the curled leaf, the first exhibition of which began to appear on the 15th, three days after the trees were in full flower. In one week after the first appearance of the curl, it was fully developed, as the season advanced with great rapidity.
What farther relates to this subject, I will detail under the following particulars:
1. The glandless varieties, as a class, were far less affected than the glanded. Indeed, the most of those were affected either in a small degree, or not at all. Now this is just what might have been expected. The glandless varieties always suffer from mildew on the extremity of the branches late in the summer, the effect of which is to dwarf the tree slightly, and so render the growth more firm, and insure the earlier maturity of the bud. There will thus be less soft and sappy wood, and fewer feeble buds on such trees. My glanded trees were nearly all affected, the most of them badly.
2. Some glanded trees that were very strong growers, whose fruit buds have stood the severe cold of winter better than any others, suffered very severely. This may seem strange and contradictory, but admits, I think, of a ready explanation. These trees had well matured their buds, and so stood the winter well while dormant; but the vigorous character of the tree caused a proportionate early and vigorous start of the circulation in the spring. This prepared them to feel a check in the circulation more fatally than trees of less constitutional vigor, which started somewhat later, and less vigorously.
As an illustration of this second fact, I observe that I have five seedling glanded trees, all very rank growers, one an early fruit, one somewhat late, and three very late, which, year by year, both before and since the advent of the curled leaf, have stood the winter well, and have been uniformly covered with flowers; and yet they have suffered peculiarly from the ravages of the curled leaf for two years past. The " Teton de Venus" also, though its fruit buds have not stood the winter well, is a very strong grower, and drops its leaves in good season in autumn, yet it has been almost ruined by the curled leaf.
* Very similar was the weather in 1850. The winncr had been unsteady and very mild. From April 24th to 27th, there were four very warm days, the thermomete r rising to 76. Then it become cold and windy. By the first of May the buds which hod been prematurely excited and then chilled, began to fall off. The flowers opened about the 12th, and the leaf bud developing immediately after, showed signs of curled leaf. From the 17lh to the 21st, inclusive, the weather was severe, exhibiting both frost and snow. Frost was subsequently reported as having occurred daring these severe days, in Canada, Boston, New-Haven and New-Jersey. Since 1842 we have suffered no untimely warm weather in the spring, equal to 1350 and 1S51. The weather from the 4th to the 8th of April, inclusive, in 1844, came the nearest to it. We have not, therefore, had the Same causes of curled leaf, at least for many years, as in 1850 and '51.
3. In all cases where the center leaves of the bud when it first opened, exhibited the curl, the shoot beneath never elongated at all, or not more than an inch or two, and then the whole withered and died under the curl.
4. In those cases where the center of the bud did not exhibit the curl, the shoot elongated regularly, although as it grew there might be curled leaves at the base, and along the sides of it. Such branches flourished, being a little dwarfed until they cast off the diseased leaves.