Diseases of Field Crops (Classic Reprint) - Hardcover

Inhaltsangabe

Excerpt from Diseases of Field Crops<br/><br/>Nonparasitic diseases are mainly the effects of soil and climatic condi tions such as moisture, temperature, and chemical substances. Direct, obvious, or easily diagnosed injuries like those caused by frost, wind, ex cess water, drought, or chemical salts (alkali) in most cases are not described as diseases under specific hosts. Viruses are foreign substances which Invade, spread, and increase in the bodies of plants, often causing specific diseases and great injury. Many human and animal diseases (measles, smallpox, rabies, foot-and mouth disease) are of a similar nature. The virus itself is invisible even under the strongest microscope and, while in many respects it behaves like a parasitic living organism, has other characteristics which make it seem a nonliving chemical substance. Most virus diseases of plants are spread by aphids, thrips, or leafhoppers which feed on affected plants and then on healthy ones.

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