. Diseases of cereal and forage crops in the United States in 1922. Grain Diseases and pests United States; Forage plants Diseases and pests United States. 250 Pov/dery caused by Erysiphe sp. Probably the most noteworthy plant outbreak of the year was that of powdery milde"/ of red clover. In 1^21 it appeared in unprecedented amounts in states in the nortlieastern quarter of the country, but during 1922 it v/as much more widely dis- tributed and occurred all over eastern United Jtates from South to North ard in eastern Canada. The accompanying shows the geographical range of
. Diseases of cereal and forage crops in the United States in 1922. Grain Diseases and pests United States; Forage plants Diseases and pests United States. 250 Pov/dery caused by Erysiphe sp. Probably the most noteworthy plant outbreak of the year was that of powdery milde"/ of red clover. In 1^21 it appeared in unprecedented amounts in states in the nortlieastern quarter of the country, but during 1922 it v/as much more widely dis- tributed and occurred all over eastern United Jtates from South to North ard in eastern Canada. The accompanying shows the geographical range of the disease. On the western limits it v;as reported only from the eastern parts od the Dakotas and Kansas, Apparently, it did not extend beyond the line of the 100th pig» 38- Distribution of powdery mildew of clover in the United States, as reported by collaborators of the Plant Disease Survey, I921 and 1922* It appeared first in the southern states early in npril and then as the crop developed, was reported farther northward appearing in the northern states during June. or not this progression from south to north indicates spread in the same direction is uncertain. It is more probable that the fungus was v/ell distrib- uted and made its first appearance in the various places at the time when weather conditions favored- Kov/ever, considerable spread undoubtedly took place during the year. A number of collaborators mention the appearance of "che mildew in a portion of a state, with subsequent appearance in other parln? The reasons for the unusual outbreak of this disease au-^ing the past two years is still somev/hat in doubt. It may be that peculiar climatic conditions have favored the unusual development and spread of a native powdery mildev/« On the other hand, there are good-reasons to suppose, oartioularHy on account of the conspicuous character cf the mildew, its apparent invatiior. cf new localities^ and because of the fact native clov
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Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1920, bookyear1923
