[1] Dr. Kathleen G. Doering, at the University of Kansas identified the spittle bug from the Illinois pecans as Clastoptera achatina, a species not hitherto recognized as an important pecan pest. Spittle bugs from southeastern pecans have been referred to a different species.—Ed.
Preliminary Results from Training Chinese Chestnut Trees to Different Heights of Head
J. W. Mckay and H. L. Crane[2]
Introduction
Many growers of Chinese chestnut (Castanea mollissima) want to know how soon their young trees may be expected to bear their first crops of nuts. This is determined by several factors, but perhaps one of the most important is the amount and kind of pruning the trees receive during the first four or five years they are in the orchard. One reason for the importance of type of pruning is the characteristic habit of the species to form branches low on the trunk, so that low-headed and spreading tops result if trees are left unpruned.
It has long been accepted by most horticulturists that any kind of pruning of fruit trees tends to be a dwarfing process. Hence, pruned trees would be smaller than similar unpruned trees. Pruning of young fruit trees, though reducing the size of the top and the number of growing points, tends to stimulate the growth of the remaining shoots. This has a marked tendency to delay the formation of fruit buds. Hence, unpruned trees come into bearing earlier than even lightly pruned trees. Tufts (2)[3] reported that lightly pruned deciduous fruit trees, such as apple, pear, apricot, and peach, came into bearing one to three years earlier than similar trees that had been heavily pruned. Crane (1) found that height of head in apple trees had little effect on yield for the first nine years in the orchard, but at the time the experiment was terminated the trees were still too young for him to expect much fruit production. He found, however, that the low-headed trees made more shoot growth and a larger gain in trunk diameter than the high-headed ones, and thus the bearing area was larger. Because the tree form of the horticultural varieties of Chinese chestnut is somewhat comparable to that of apple varieties, it would be expected that the two might give similar growth and yield responses to pruning or training procedures. The experiment described in this paper was initiated for the purpose of determining the response made by trees of Chinese chestnut varieties pruned and trained to three heights of head.
Experimental Procedure
The three varieties used in the experiment are Meiling, Nanking, and an unnamed variety carried under the accession number 7916. The last variety is characterized by dwarf, heavy-bearing trees that mature their crops very early in the fall, whereas Meiling and Nanking are vigorous, fast-growing varieties that mature their nuts in midseason. In the early spring of 1948 thirty-six two-year-old grafted trees were planted 25 feet apart in the orchard in four short rows of nine trees each. The three treatments consisted of (1) no pruning; (2) pruning to a 2-foot head; and (3) pruning to a 4-foot head. Three trees, one of each variety, were included in a plot or treatment. Thus, the experiment was arranged in a randomized block design with the three treatments randomized in each row and the four rows serving as replications. Each spring the trees received a liberal application of a 10-6-5 fertilizer. Strips six to eight feet wide on each side of the contoured rows received frequent cultivation each growing season, while strips of orchard grass sod were left between the rows to prevent erosion. The soil is Riverdale (tentative series) sandy loam that had been in orchard grass sod for ten years before the experiment was begun. It has been necessary to spray the trees each year with DDT, parathion, or both to control Japanese beetles and mites.
Pruning of the trees was begun during the first winter following the planting in the orchard, but only a few of the lower limbs were removed in order not to dwarf the pruned trees severely. The second winter a few more lower limbs were removed and at this time the two-foot-head treatments were complete. A third pruning was necessary before the heads of the trees in treatment three could be raised to four feet. Detailed records and measurements were made of the diameter of each tree trunk one foot above the ground, and of the weight and number of nuts produced (yield).