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Page:Popular Science Monthly Volume 72.djvu/414

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POPULAR SCIENCE MONTHLY

cially dark color, very useful in Australia for the destruction of various scale insects, was introduced by Koebele into California while on his second mission to Australia in 1893. It naturalized itself and plays an important role in fighting the black scale of the olive. A hundred thousand of these insects were distributed in different districts. In different localities they multiplied in a prodigious way, and proved to be particularly efficacious in the moist climate of the seashore. Mr. Cooper, president of the State Board of Horticulture, had such confidence in the efficacy of this Rhizobius and other ladybirds that, yielding to a perhaps exaggerated enthusiasm, he renounced for a time all other intervention, and, in order to allow them to multiply at their ease, he suspended all treatment. According to him, to spray trees upon which there is Rhizobius is a crime and should be severely punished.[1]

Attempts to Fight the San Jose Scale by Means of Ladybirds.—The disasters caused by an insect commonly known as the San Jose scale in the United States are well known. The damage done to the fruit trees can only be compared in intensity to that done in our country by the Phylloxera, and about 1898, the fear that it would be introduced into Europe occasioned prohibitory, special legislation on the part of European states. Since it was a scale insect, it was natural to search for an enemy which would approximate the rôle of Novius cardinalis, but no one knew the original home of the San Jose scale.

Australia was considered for some years as responsible. Finally, they concluded that it might be Japan, and Mr. Marlatt, first assistant of the Division of Entomology, Department of Agriculture, was sent on a mission, in 1901-2, to the extreme orient to solve the question, and he established in a positive manner the fact that the original home of the San Jose scale was the north of China, where he found it occurring upon small wild apple trees, in the mountainous country. There he found, at the same time, with the scale insect a ladybird, Chilocorus similis Rossi, which, both in the larval and adult stages, feeds on the San Jose scale. This ladybird is an insect widely spread, not only in China, but throughout all of Asia and the south of Europe. The San Jose scale is, then, not its only food, but it can live at the expense of different scale insects. Therefore, samples of this insect, coming from China and offering the best possible conditions for adaptation to the struggle against the San Jose scale, were sent to Washington, and all precautions being taken, they were bred with great care in the Bureau of Entomology, first in cages and afterwards in an experimental orchard.

They were thus produced in sufficient quantity, so that for several years they could be sent to different States. The colonies which were


  1. The attempt to acclimatize Rhizobius ventralis in India and Ceylon, undertaken by Froggatt and Green, did not succeed, probably on account of unfavorable climate.