. Manual of fruit diseases . Fruit. APPLE DISEASES. Fig. - Scab on young apples. Lesions on both the fruit and pedicels. Cause of The apple-scab pathogene is a fungus known by the name Venturia inaequalis. It passes the winter in the old fallen leaves as immature perithecia. With the advent of spring these sexual fruit- ing bodies come to full maturity by the time the blos- som-buds are ready to open. These spring activities of the parasite are characterized chiefly by the for- mation, within the perithecia, of ascospores which constitute the principal in- oculum for the first
. Manual of fruit diseases . Fruit. APPLE DISEASES. Fig. - Scab on young apples. Lesions on both the fruit and pedicels. Cause of The apple-scab pathogene is a fungus known by the name Venturia inaequalis. It passes the winter in the old fallen leaves as immature perithecia. With the advent of spring these sexual fruit- ing bodies come to full maturity by the time the blos- som-buds are ready to open. These spring activities of the parasite are characterized chiefly by the for- mation, within the perithecia, of ascospores which constitute the principal in- oculum for the first infections. Inoculation is brought about through the agency of the wind. The ascospores are forcibly discharged into the air from the perithecia imbedded in the old leaves on the ground, and these spores, being extremely light, are carried to the opening buds. Spore discharge is con- ditioned by (1) the maturity of the ascospores themselves. They are maturing during a period of about one month begin- ning approximately at the time the blossom-buds are ready to open. (2) The occurrence of rain-periods when the ascospores are mature. It has been estimated that in forty-five minutes of wet weather at the proper time no less than eight billion asco- spores might be discharged from the old fallen leaves under a large apple-tree. These figures indicate how one may account for even the most abundant primary infection of young leaves and blossoms that has ever been recorded. Since the lower surfaces of the unfolding leaves and the young fruit-pedicels are. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hesler, L. R. (Lexemuel Ray); Whetzel, Herbert Hice, 1877-1944. New York : Macmillan
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1917
