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Page:Popular Science Monthly Volume 72.djvu/373

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369
INSECTS INJURIOUS TO AGRICULTURE

in the north of the kingdom, in the province of Traz-os-Montes, where it had previously made its appearance.

Icerya purchasi and Novius cardinalis in Italy.—Icerya purchasi was introduced accidentally into Italy at the end of the year 1899 or in the spring of the year 1900, without any indication of the origin of the infection. But it was observed for the first time, in the month of May, 1900, at Portici, near Naples. It was there found in a little garden upon orange trees, and was represented only by a rather small number of individuals. The proprietor of the garden, ignorant of the character of the insect and of the danger arising from its presence, took no trouble to destroy it, and the scale insect, able to develop freely without enemies, spread so rapidly that in the autumn it already covered the bark and leaves of the oranges upon which it had first been observed. Startled at this sudden invasion, but not yet deciding to apply to competent persons, the owner of the garden tried to stop the trouble by cutting down the most infested trees without bothering himself with those that were not badly infested, so the infestation continued. The eighteenth of November, the same year, the entomological laboratory was notified of the occurrence; and Professor Berlese, the director of the laboratory, recognized the species as Icerya purchasi. The insect was still very localized, and it was found at this time only in the adult condition in the little garden which was the center of the infection, and upon a large bay tree which occurred in another neighboring garden, occupying a high position and whose branches overhung the infested garden. This bay tree, on account of the strong winds which blow at that time of the year, constituted a center especially favorable to the dispersion of the larvæ into the surrounding trees, and, in fact, the larvæ were found in all the little gardens about. An examination was made and it was found that the infested area did not exceed one hectare.

On account of the small spread of the insect they tried to exterminate it by an energetic application of insecticides. The first thing done was to cut down the bay tree, which was the principal center of diffusion, and to burn it after having cut off and disinfected all the branches bearing leaves. In the infested gardens all the affected trees were cut back and all the branches were disinfected with a solution of rubina.[1] The low-growing plants were treated with sprayings of the same insecticide. They hoped to rid these of the insects in this way, but in the following spring living larvæ, still very numerous, were found crawling over the plants treated, and then, despairing of destroying them with insecticides, they had recourse to Novius cardinalis. At Professor Berlese's request successive sendings were forwarded from

  1. Rubina is a mixture of equal parts of soda and tar, recommended by Berlese, and very much employed in Italy.