Cooperation in Diller's Underplanting and Girdling Method for the Establishment of Chestnut Forest Stands. In the 37th Annual Report of our Association for 1946 is printed a paper by Dr. Jesse D. Diller of the Division of Forest Pathology, U.S.D.A. entitled "Growing Chestnuts for Timber" pp. 66-68. Many people seem to think that all you need to do when planting a tree is to stick it in the ground—just any ground. This may be true of some kinds, but is certainly not true of the chestnut. For best growth and development the chestnut requires a fairly deep, well-drained soil, rich in mineral elements and humus, with a fair degree of moisture and plenty of sunlight. Two things chestnuts will not endure are shallow soil and drought, the latter often depending on the former.
As tree indicators of the kind of site required for the establishment of a chestnut forest Dr. Diller has chosen yellow poplar, northern red oak, white ash, sugar maple, and yellow birch, with spice bush as a shrub indicator and maiden hair fern, bloodroot and other herbs as herbaceous indicators. Using a small area of about one eighth of an acre, Dr. Diller's plan is to girdle all the trees and then underplant with chestnut seedlings. He says: "As the girdled overstory trees die they gradually yield the site to the planted chestnuts in a transition that does not greatly disturb the ecological conditions, particularly of the forest floor. Rapid disintegration of the mantle of leaf mold is prevented by the partial shading which the dead or dying overstory, girdled trees cast." This may seem to some a rather drastic method, but when so much is at stake, namely the re-establishment of the chestnut in our forests, it would seem a justifiable experiment on a small area.
In March, 1947, we supplied Dr. Diller with one hundred seedlings, one or two years old, of our best stock, for underplanting in two of these selected sites, fifty seedlings each, namely on the estate of Mr. E. C. Childs at Norfolk, Connecticut, and on lands of the T. V. A. at Norris, Tennessee. Our best wishes for a successful blight-resistant future go with these little trees.
Grafting Work. We are continuing with our method of "inarching" young "suckers" from below a blighted area into the trunk above the lesion, the diseased tissue of the lesion being first cut out. This method (see Brooklyn Botanic Garden Chestnut Breeding Project. 35th Annual Report of Northern Nut Growers Association for 1945. pp. 22-31—1945) is entirely successful in case we desire to preserve partly resistant hybrids of good parentage for future breeding and for scions. (Figs. 1 and 2) But inarching of the native chestnut is for the most part unsuccessful because the fungus grows too rapidly and girdles the stem, killing the parts above before the inarched tips of the suckers can take hold. There seems to be a certain relation between the amount of disease resistance in the tree and the possibility of restoring it to health by the inarching method.
By the common ordinary cleft-graft method, using Japanese, or better, Chinese stock we are adding to the supply of our most desirable hybrids.
Insect Pests. The spring canker worm, Paleacrita vernata, has not been destructive either in 1946 or 1947 and no special preventive measures have been taken. Japanese beetles have done a little damage. This year the first one appeared July 11. We find the best method with these is to pick them off at dusk after they have settled themselves for a night's sleep, dropping them into kerosene oil. Under these conditions they will usually slip readily off the leaf into the oil. One thing I should like to emphasize (which probably others also have noticed) is that new beetles keep coming, day after day. Apparently the adults are issuing from the ground all summer. Last year I found a few Japanese beetles in November. So one must keep continually on the job all through the season. This summer (1947) we have had a spray program of three sprayings, August 15, 30, and September 10, with "Deenate" (fifty percent DDT) to destroy the chestnut weevils which appeared for the first time rather extensively in our Hamden plantations last year. (See E. R. Leeuwen; DDT for chestnut weevils, American Fruit Grower 67: 28. 1946) This spray, which we have used on the ground as well as on the young burs, kills Japanese beetles as well as the weevils. This fall I have seen very few weevils in our whole crop of nuts.
The louse, Callaphis castaneae, appeared on July 5, 1947, at least the leaves became so much curled that its presence was then noticed. Two spraying on successive days with nicotine sulphate ("Black Leaf 40") were sufficient to control it. With us this insect attacks leaves of American stock only. Japanese-American hybrids are also susceptible, but not Chinese-American or American-Chinese. The lice, of an orange color, congregate in great numbers along the midrib of the leaf, sucking out its juices.
This summer, perhaps on account of the unusual almost tropical weather conditions—hot and humid with continually recurring showers—we have been harassed by a new pest which has appeared in one of our plantations only sparingly for five or six years—a mite, which Connecticut Agricultural Experiment Station authorities say is Paratetranychus bicolor. Affected leaves have a whitish or grayish color chiefly along midrib and principal veins, due partly to the deposit of the creature's shells on molting, and partly to injury to the tissues of the leaf. Hexa-ethyl tetraphosphate, known in the trade as "Killex 100," was used effectually twice as a spray. Unfortunately this chemical has no ovicidal properties, so that a second spraying was necessary to kill the mites newly hatched out from thousands of eggs. We are informed that DN 111 will kill the eggs as well as the mites and will kill aphids at the same time. The mites seem to prefer Chinese chestnut leaves, but this summer they didn't seem particular and spread from one badly infested tree as a center.
