Abstract

                                It is a matter of common experience that crops subjected to extensive and intensive culture are among those which are victims to the largest number of pests and diseases. The truth of this statement is in a large measure attributable to the great amount of attention bestowed by the scientist to the health of the plant by virtue of which all the pests and diseases which occur on the crop are recorded and studied. At the same time the fact cannot be denied that man's intervention in the natural development of plants and his unscrupulous exploitation of their resources renders them more susceptible to the inroads of insects, fungi, bacteria, etc.

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