Prof. A. W. Herrick, Ithaca, N. Y.
With a residence of a little over a decade in the South, I became more or less intimately connected with a good many of the nut growers of the section, especially the pecan growers. I found them there an intelligent body of men.
The President has asked me to talk just a little on the hickory bark borer. While in Mississippi, I first came into contact with the hickory bark borer by its work on the hickories on the lawn in front of my house and on the Campus. It began killing the trees. I had ten or a dozen trees on the lawn that were from six to eight inches through, and they had made a fine growth but they began suddenly to die. First, I noticed the leaves falling in the summer time, then later in the winter the branches began to die at the top. On investigation, I found that it was this little hickory bark borer. We carried out, as a result of that investigation, a few experiments, and extended them over the Campus, following the recommendations of Doctor Hopkins of the Department of Agriculture, Washington. The results were pretty gratifying. I was able to save those trees on the lawn, and during three or four years succeeding the time we got these experiments into practice, no more had died, and they had kept on making a good growth; and I believe the ravages of the beetle had been checked.
The little beetle belongs to a family called the Scolytidae—very small beetles that burrow through the bark of trees, and between the bark and the wood, partly in the bark and partly in the wood. These beetles are interesting in their life history. The female bores through the bark, and then she builds a channel partly in the wood and partly in the bark. She goes along and digs out little niches all along, and in each one of these, deposits a tiny white egg. That soon hatches into the small grub, and the grub begins to burrow out to get his food, and you will find these little burrows running out from the main burrow of the mother beetle. When these grubs reach their growth, each one of them comes out and bores a little shot-hole-like round hole through the bark, so that a tree that is pestered with it will finally have the bark full of these little round holes. You have probably seen a similar thing in peach, plum, and cherry trees.
The hickory bark borer is found all over the eastern United States, from Canada to the Gulf, and as far west as Nebraska. It attacks hickory trees and walnut trees, and as far as I can find, the authorities say probably the pecan. I never found it on the pecan in the South. If it does ever come to attack it in any numbers, it will be a serious pest from the nut grower's point of view.
In this state, it was first noticed by its work on hickory trees in the vicinity of New York City, and it is killing a good many of them. To show its dangerousness—on the estate of Mr. Wadsworth at Geneseo in 1900 and 1901 over an area of two hundred acres, it destroyed ninety to ninety-five per cent of the hickories. It really becomes a most injurious pest. These little fellows running under the bark cut off the cambium layer and girdle it, and kill the tree as effectually as if we were to take an axe and girdle it. A few can girdle it very quickly.
An infested tree in the summer shows some characteristic effects. The leaves begin to dry and wither, and finally drop. The adult beetles, when they come out in June and July, attack the petioles, leaves, and terminal buds for food, then go down to the larger branches and trunks, and burrow to lay their eggs. The younger top branches begin to die. If you look, you will very often find a little white sawdust in cracks in the bark. That is an indication that they are present. If you take off the bark, you will find such an appearance as I have shown you. Later, you will find these holes all over, showing the work of the beetle.
I will give the life history of the insect very briefly. The insects live over the winter under the bark, as grubs, and in the spring they change to the pupa form, and come out along in June and July. Some may be as late as August. Those beetles go to the branches and leaves, and soon begin laying their eggs. There is only one brood a season, in this locality at least. In a longer season, farther south, there might be more than one, although my experience in Mississippi was that there was only one brood.
A word regarding methods of control. You can readily see that there is no way of getting at the beetle with insecticides after they have gotten under the bark. Doctor Pelt mentions the value of spraying the trees in summer to kill adults when they are feeding on the petioles and probably the terminal buds and younger twigs. It is rather doubtful whether it would pay to spray hickory trees at that time, although the expense of spraying large trees is not so great as you might think. We have had experiences here, because it fell to my lot to spray all the elm trees on the Campus last year. I kept very careful account of this. We sprayed between five and six hundred trees. About one hundred are scattered over the hillsides west of the buildings, some a mile from the water supply. We did the work for about eighty-eight cents apiece, each tree having a thorough spray. The largest trees on each side of the street we gave two sprayings for a little less than forty cents apiece.
The real method of getting at this hickory bark borer is for everybody to cooperate and cut those trees out, or at least the affected parts of the tree, before the first of May. I know of no other effective method of getting them. Cut them out and burn them. Some say, peel off the bark and destroy that; but if you do that, you have got to cut off the smallest branches and burn those, and I am afraid you would not get all of the grubs. But it is better, if you can, to actually dispose of the whole tree in some way.
There were three trees on the lawn infested and dying. I cut those out in February, and that evidently stopped the ravages of the beetle. That was carried on over the whole Campus, and it must have stopped the injuries, because during the three or four years I was there after that, we had no dead hickories from that cause.
That is evidently the only method of getting at them. It has been wondered if we might not go to the Commissioner of Agriculture, and ask him to take this matter in hand and force people to cooperate, because it has become a rather serious problem. It is evident from a perusal of the law that he has power to do that, and perhaps if this Nut Growers' Association wishes to pass resolutions to bring before Commissioner Pearson, they might induce him to take some steps to control this hickory bark borer.
President Morris: If we have evidence that the hickory bark borer can destroy ninety per cent of the hickory trees on an estate so well cared for as the Wadsworth estate, it indicates a menace to the whole hickory forests of the North. In view of this fact, in view of the possibility of ninety per cent of our hickory trees being destroyed by this beetle, it seems to me that we should ask our Commissioner of Agriculture to take charge of the matter, as he has taken charge of the chestnut bark disease, requiring the cooperation of the people in disposing of a question which is so vital among the economic problems of our state. Is there any discussion on this paper?
Doctor Deming: I would like to read an extract from a letter addressed to me by H. W. Merkel, Forester of the Bronx Zoological Park:
"Under Chapter 798 of the laws of the state of New York, passed on July 26th, 1911, the Commissioner of Agriculture is authorized and charged with preventing the spread of just such pests as the Hickory bark-borer, and if this matter be called to his attention promptly and in the right way by such responsible and interested parties as the Northern Nut Growers' Association, there is, undoubtedly, still time to check the further spread of the pest. We have from now until June (the time when a new generation of beetles will emerge) to take whatever action is necessary, and I urge upon you to persuade the Nut Growers' Association to take the necessary steps. I would be glad to have a conference with you on this matter, and will be glad to help you in any way you wish."
I would suggest the appointment of a committee to draw up a strong set of resolutions to be sent to the Commissioner of Agriculture of the State of New York and perhaps of other states, and to the Department of Agriculture. (Referred to Executive Committee for report.)
President Morris: We will have next in order the paper by Professor Lake on the Persian walnut in California.