It has been shown that a cut made pointed at the top and bottom heals much faster than one rounded. The edges of the cut should be made with care so as not to injure the cambium. The chips of diseased bark and wood should not be allowed to fall on the ground then to be forgotten. A bag fastened just below the canker will collect most of this material as it is gouged out and prevent possible reinfection, which might take place if the material were allowed to scatter down the bark. Canvas or burlap spread around under a small orchard tree might be sufficient to catch all of the diseased chips of bark and wood cut out of the lower infections. This diseased material should be burned together with blighted branches. After completely cutting out all of the diseased parts the cut surfaces should be either sterilized or covered with a waterproofing which combines a fungicide with a covering. Among these might be mentioned coal tar and creosote, or a mixture of pine tar, linseed oil, lamp black and creosote.
The trees which have been killed by blight, or nearly girdled, have been overlooked. These should be cut off close to the ground, the stump peeled and the bark and unused portions of the tree burned over the stump. The merchantable parts of the trees should be removed from the woods promptly, as all dead unbarked wood furnishes an excellent breeding place for the blight fungus.
Third, what means in the future can be undertaken to keep a tree healthy, that is, to prevent reinfection. The spores may be carried by so many agents that it is difficult to prevent reinfection. However it is clear that the farther infected products or trees are removed from healthy trees the less liable they are to have spores carried to them. Cooperation with nearby owners of diseased trees will help solve this problem.
Spraying on a large scale has only been carried on, so far as I know, on the estate of Pierre DuPont, Jr., at Kennett Square, Pennsylvania. At this place there are many large chestnut trees ranging from sixty to ninety feet in height, many of which were planted some sixty-five years ago. Mr. R. E. Wheeler started the work of cutting out diseased limbs and cankers in October 1911, and began spraying with Bordeaux mixture in April 1912. The formula 5-5-50, five pounds of copper sulphate and five pounds of lime in 50 gallons of water was found to be injurious to the foliage in the Spring. This was changed therefore, to 4-5-50, which had one pound less of copper sulphate. This did not seem to injure the foliage.
About 70 trees were sprayed twenty times during the season. Nearly all of these were gone over four times to remove diseased branches and cankers, once in October 1911, then in early summer and again in September and November 1912. As an example take tree No. 6 which was studied, December 14, 1912. It is 39 inches in diameter at breast height, and approximately 70 feet in height. On this one tree six diseased limbs were removed, and sixteen cankers were cut out. Of these sixteen, two infections continued, that is, were not completely cut out, and had spread; three had infections below old limbs which had been removed, and eleven were healing over. This tree was about 1000 feet away from other badly infected trees, though but 25 feet away from other chestnut trees in the same row. The experiment of Mr. DuPont in spraying shows what can be done on valuable lawn trees. On the whole, these trees look well and healthy. Trees which were not sprayed over three times and were within 50-100 feet from badly blighted trees, became infected in so many different places that it will be necessary to remove them.
One of the problems to be solved next year will be that of the least number of sprayings which will be effective in preventing new infection.
The Chairman: The question of the chestnut blight is now open for discussion.
Mr. Littlepage: I should like to ask these gentlemen how far west they have heard of chestnut blight—that is, heard of it with any degree of authenticity, and also whether or not they care to express an opinion as to what the prospects are in the middle west, say out in Indiana, Illinois and Ohio?
Mr. Pierce: In answer to that question, I will say that in Pennsylvania we have found infections in Wayne County and also in Fayette County, both near the western extreme of the state, but those have been attended to, very largely, and the boundaries closely determined. In Ohio there have been several reports of the blight being found, but I don't think either of the reports have been proven. There has been a fungus that I have spoken of as the Connellsville fungus, that has been all around in that neighborhood, south-western Pennsylvania and eastern Ohio.