Sanitation is one of the more important means of control. Infection generally takes place at the blossom end of the fruit as it reaches maturity. and rainfall encourage disease development. Leaves are the first tissue to be infected. In the spring spores are formed in the cankers. The organism overwinters in cankers, decayed fruit, and dead wood. Twig infections are small, sunken, reddish-brown areas. At maturity the spots are purplish cast with brown centers. Infected leaves are covered with many small purple specks. A circle of raised dark postules are formed in the center of the spot. The spot at first is light brown but darkens with age. Once the disease begins to show up, spray at seven day intervals for two or three applications.īlack Rot (fungus – Physalospora obtusa): Black rot is a firm-textured rot. Remove all broken limbs and decayed fruit. Good sanitation will help reduce losses from this disease. A temperature of 85oF and light rain favor development of the rot. Symptoms are first noticeable in mid to late July. A broken limb or twig will serve as an overwintering site. The organism overwinters in decayed fruit and in cracks on the old bark. With age the spots become almost black and have a saucer-shaped depression. Infected fruit are characterized by a firm rot which forms a circular light brown spot. Fungicides should be applied at full leaf development and continued at two week intervals for four sprays.īitter Rot (fungus – Glomerella cingulata): The fungus attacks apples and pears and enters the fruit through uninjured skin. Secondary infection can occur during the spring and summer when the temperature is near 75oF. After infection there is a period of one week before symptoms are observed. In the spring, twig lesions produce spores which are washed by rainfall to leaves. Lesions also occur on twigs and are the overwintering inoculum. They sometimes coalesce to cover a large portion of the fruit surface. Fruit spots are one-fourth inch in diameter, black, and slightly depressed. As the spots get older, they develop purple margins with brown centers. Leaf Blight and Fruit Spot (fungus – Entomosporium maculatum): Leaf spots first appear as small purple spots which enlarge. Reapply a bactericidal spray to an orchard if it is damaged by hail or receives a heavy rain immediately after an application. Apply bactericides on 5 day intervals between early bloom and late blooms.Make pruning cuts 8 to 12 inches below visible sign of disease. Remove overwintering bacteria cankers by pruning. Summer pruning may encourage tender succulent growth which is more susceptible to disease.
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