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Page:Popular Science Monthly Volume 72.djvu/368

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364
POPULAR SCIENCE MONTHLY

The Use of Novius Cardinalis against Icerya

Icerya purchasi and Novius cardinalis in America.—Icerya purchasi is a scale insect living upon different trees and particularly upon citrus trees. It is originally from Australia, and was accidentally introduced, about 1868, into California where it did enormous damage, and threatened to ruin the cultivation of oranges and lemons. All attempts to fight this Australian insect with different insecticides were vain. It continued to spread in a progressive manner from the orchards that had already been annihilated or were in bad condition.

Riley, then director of the Division of Entomology of the Department of Agriculture, at Washington, thought of utilizing the natural enemies of the scale insect. Ascertaining that in Australia, its original home, it did not seem to be seriously injurious, and to be without importance from the economic point of view, he was led to think that it probably was held in check there by parasites. Investigations which he made on this question having confirmed his ideas, he made every effort to accomplish the desired end, namely, the acclimatization of the natural enemies of Icerya in California. Finally, after numerous appeals to the government, he was able to arrange for a sending of two agents of the Division of Entomology to Australia on the occasion of the exposition at Melbourne, in 1888, with a credit of $2,000. One of these agents, Mr. Koebele, was especially instructed to search for parasites of Icerya.

On his return he brought a collection of the natural enemies of the Australian scale insect. Among these there were a hundred living specimens of Novius cardinalis. It multiplied so rapidly that in the following year, 1889, they could distribute to the fruit growers of California 10,000 specimens. A year and a half after its introduction it had relieved the region from Icerya, and had reduced their number to a practically negligible quantity. According to witnesses this deliverance possessed for the inhabitants of the country an almost miraculous character. Immense groves of oranges bearing no fruit, covered with a horrible, white leprosy composed of the Iceryas, and which seemed irremediably lost, suddenly took on a new vigor and furnished abundant crops. Now the only natural means necessary to hold Icerya in check consist in sending a small number of Novius cardinalis to start colonies in the district where the scale insect shows a tendency to regain its foothold. In this way reserves of Novius are constantly kept on hand for exportation, either to the different districts of the State of California or to foreign countries, and the State Board of Horticulture of California has constructed small boxes of glass and wire gauze of octagonal form, 16 feet in diameter and 18 feet high, allowing the Iceryas and the Novius to live upon the trees surrounded in this way.