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ber 1, 1913, a part of this block was treated with scalecide at varying strengths, and a few trees were treated with carbolineum and its emulsion.' as indicated in table 1. This experiment was closely watched the following spring, but no injury to the trees could be noted except that the carbolineum-treated trees did not seem so vigorous as the others. However, they grew, and in 1916 they were large, healthy trees. Examination and careful count of the burrows in all the trees was made on June 17, 19:4. The infestation is shown in table 1:
In the spring of 1914 a series of experiments was undertaken in a large nursery. Stock three years old was chosen, as it was the most readily available at the time. Badly infested trees were selected at one side of a large block which had been recently dug Directly across the roadway was a block of young poplars. On March 31, scalecide at varying strengths. carbolineum, and carbolineum emulsion were applied to the trunks from the ground up to the young growth. The day was fair, but rain began to fall before the various treatments were completed. However, the rainfall was slight, so that it should have had no effect on the insecticidal qualities of the preparations. The treated trees were examined carefully on May 14, 1914.
The various treatments had no effect on the growth of the trees, every tree growing vigorously and there being no difference, as far as could be detected, between the checks and the trees under experimentation. In the checks the larvæ were actively at work and their abundance was
? The carbolineum emulsion was prepared by dissolving 1 pound of sodium carbonate in i quart of hot water, adding i quart of carbolineum, and stirring the mixture vigorously,
trees, and this could be seen for a
indicated by the amount of sawdust exuding from the numerous burrows.
The trees were again carefully examined on June 18, when the previous observations were confirmed. The checks and the trees treated with scalecide were nearly all badly infested, many trees having from eight to ten borers present, while a few, both of the treated trees and the checks, were apparently free from infestation. The trees treated with carbolineum and its emulsion were growing even more vigorously than were the untreated trees, and not a trace of the work of the borer in any one of the twelve treated trees could be discovered. These preparations colored the trunks of the trees deep brown, but other than that no injury could
Experiments in 1914-15 In view of the possibility that such perfect control might be due to other causes than the effect of the treatment, a larger series of experiments was planned for the fall of 1914 and the spring of 1915. The miscible oils were discarded, and kerosene emulsion, which had been recommended for the control of the locust borer (Cyllene robiniæ), was given a trial. In a block of over ten thousand trees, ready for digging in the fall of 1915, rows were selected at the end showing the greatest amount of the feeding work of the beetles. On December 4, 1914, groups of twenty trees each were treated respectively with pure kerosene emulsion, carbolineum emulsion, and carbolineum. Rows for checks were left between the treated rows. The material was applied directly to the trunks, up to the younger growth. On April 9, 1915, twenty-five trees were treated svith pure kerosene emulsion, fifty with carbolineum emusion, and twentyeight with pure carbolineum. Just previous to these treatments the trees
n the whole block had been pruned carefully. The material was carefully brushed over the trunks, covering all the cut surfaces of the recently removed branches.
The trees were examined on June 28. The block as a whole showed severe infestation, sawdust being present at the base of a great many
long distance down the nursery row.
brown color but no indication of borer work (fig. 125). The kerosene emulsion had no appreciable effect, nor did it injure the trees though it was
applied in large quantities.
The treatments applied and the results obtained are shown in table 2. Kerosene emulsion applied pure in December seems to have had some effect, but one cannot safely draw conclusions from the result shown. The infeståtion of 30 per cent is high, though the average number of larvæ per tree is at a
minimum. The carFIG. 125. TREES TREATED WITH CARBOLINEUM AND ITS bolineum applied EMULSION, SHOWING DARKENED TRUNKS. CHECK ROW either pure or in emul
sion gave almost absolute control. This seems to the writer to be a very simple and effective means of control under nursery conditions.
* One half-grown larva was found in July, in an area evidently not thoroughly treated.
Experiments in 1915-16 The success of the preliminary experiments led to the trial of the carbolineum treatment on a commercial scale. In the fall of 1915 arrangements were made to treat two entire blocks of poplar trees in each of two large nurseries. This was made possible by the courtesy of the owners, who provided all the material, help, and necessary equipment, the writer
taking charge of the work. Each block contained approximately fourteen thousand trees. Owing to the excessive snowfall during the winter of 1915-16 it was not possible to apply the carbolineum as early as was intended. The application was further delayed somewhat in order that the trees should be pruned.
On April 8, 1916, twenty-one rows in one block were treated. As the day was cold, threatening snow and sleet, the work was discontinued During the following day over three inches of snow fell, and the remainder
of the block was not treated until April 13. In the meantime the borers had begun feeding; in fact they had been active since about the early days of April. The results of the treatments in this block are shown in
It is seen from table 3 that practically absolute control was obtained with the carbolineum treatment. Unfortunately for the experiment, the entire check row did not show a high percentage of infestation, but it is sufficient to indicate that the treatment was effective.
In addition to the carbolineum, a high-grade creosote was tried in a limited way. The creosote also gave perfect control, and this promises well, for the row treated stood directly next to the check row.
The carbolineum gave the bark of the trees a deep brown color but it in no way affected their vigor. This brownish coloration gradually becomes reduced during the summer, but treated trees can be recognized easily at least three years after the treatment.