Vocabulary

deviation – відхилення

adverse – шкідливий

mite – маленька істота

rot – гниття, гниль

canker – червоточина

blight – скручування

gall – жовч, садно

incite – збуджувати

corky – корковий, пробковий

scab – парші (хвороба рослин)

angular – кутковий, кутастий

DESTRUCTIVE FUNGI

The majority of plant diseases are incited by fungi. Fungus diseases have been observed and commented on since ancient times. Biblical records mention blights and mildews on the cereal and vine crops of the ancient Hebrews. Fungus diseases were responsible for several major catastrophes in various parts of the world. Prominent among these fungal diseases was the late blight, a disease of the potato, which invaded Europe after 1845 with particularly devastating results in Ireland. Powdery mildew of the grape, native to America, became established in France and nearly wrecked the French wine industry. A parasitic root fungus, Hemileia vastatrix, destroyed the coffee plantations of Sri Lanka and other Oriental countries. In the United States the American chestnut, an important timber, nut, and tannin-producing tree, was subsequently virtually eliminated by an introduced Asian fungus. More than 1400 species of rust fungi, all parasitic, and several hundred species of smut fungi occur in North America. Equally large numbers of fungi in other groups produce a large array of diseases characterized by leaf spots, ulcerous lesions, blights, powdery and downy mildews, cankers, wood rots and stains, root rots, wilts, club root, and various other symptoms.

Viral infections

The viruses cause as wide a range of host reactions as do the bacteria and the fungi. The number of recognized virus diseases of plants has increased rapidly in recent years. Typical symptoms of viral infections include mosaic patterns, yellowing of foliage, veinclearing, ring spots, stunting and premature death, malformations, and overgrowth. Under some conditions the symptoms may be masked. Such virus diseases as peach yellows, tobacco mosaic, potato-leaf roll, and curly top of beets have been studied intensively because of heavy losses to U.S. crops afflicted with these diseases. All economic plants suffer from one or more of these obscure but potentially dangerous diseases. Virus diseases are infectious and are transmitted largely by insects. Control of these insects is the best means of reducing the disease incidence. Virus infections also may be transmitted in the process of budding or grafting, by contamination of the soil, and less commonly by means of seed or parasitic flowering plants. Among the flowering plants or so-called higher plants are a few true parasites that cause injury or death to their hosts. The mistletoes, dodders, and root parasites of the genera Striga and Orobanche (broomrape) are the more common of these parasitic plants.

Vocabulary

mildew – мільдью (шкідник рослин)

devastate – спустошувати, розоряти

wreck – руйнувати

rust – сажка (хвороба рослин)

array – велика кількість, безліч

downy – пухнастий; горбкуватий

viral – вірусний

stunt – зупиняти зріст

premature – передчасний

to be afflicted with – хворіти на

obscure – прихований, непомітний

transmit – передавати

contamination – забруднення

dodder – повій, березка

NEMATODES

Nematodes, or roundworms, are an important cause of disease in plants. For many years attention was focused on the root-knot nematodes, which cause fleshy root knots or galls on plants. More recent investigations were concerned with other species, including the stem or bulb nematodes, which live in the leaves, stems, bulbs, and roots of narcissus, phlox, and many other plants, and the leaf nematodes, growing in herbaceous plants including the begonia and chrysanthemum. The golden nematode of the potato plant and of related plants and the soybean cyst nematode are recent introductions into the U.S. that are causing increased concern.

ENVIRONMENTAL ENEMIES

Nonparasitic diseases attributable to adverse environmental conditions are numerous and include many of economic importance. Major causes of these diseases are excessively high or low temperatures, soil-moisture disturbances, atmospheric impurities, lightning, and nutritional disorders. Low temperatures, for example, are responsible for winter injury to fruit trees and potatoes, and high temperatures produce such disturbances as water core of apple and heat canker of flax. Excessive or irregular water supplies cause a variety of troubles, such as blossom-end rot of tomatoes. Disease-producing atmospheric impurities include escaping illuminating gas and smelter fumes; the latter in particular may be responsible for widespread killing of crops and forests. Lightning frequently causes injuries to plantings of cotton, bananas, sugarcane, potatoes, and many other field crops. Excessive soil acidity adversely affects many plants; on the other hand, high alkalinity may be deleterious. An excess of nitrogen or any other substance required for normal growth may cause abnormalities in plant development. Mineral deficiencies also cause diseases, and the characteristic symptoms produced by lack of each of many minerals are well established.