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Leaf edges turning bright yellow but inside leaf remaining green are signs of potassium insufficiency. The symptoms first appear on older leaves, and the leaf edges quickly become dark. A broad yellowing indicates a nitrogen deficiency. Yellowing starts with older, inner leaves.
Black knot is a disease that is most severe on cultivated crops in orchard and ornamental planting situations. Black knot appears to be a minor problem on Prunus species found in forest situations, where susceptible trees are surrounded by many nonsusceptible species of trees.
Black knot is a fungal disease, caused by Apiosporina morbosa, that attacks stone fruit species in the genus Prunus. Black knot is known for irregular, thick, black swellings on limbs. Severe infestations can reduce production drastically, reducing infected trees to a worthless condition in a few years if the disease is not addressed.
The most obvious sign of black knot is the hard, black, swollen galls, commonly called knots, on branches and twigs. Black knot also infects fruit spurs, and sometimes trunks. Infected trees may produce few flowers or fruit.
the knots darken and appear to have a hard, brittle texture (Fig. 2). The hard, black knots are the typical symptoms associated with the disease. Knots vary in size from approximately 1-30 cm (0.5 to 12 in.) in length and from minute measurements to 5 cm (2 in.) in circumference. The infected twigs
The main symptom of Dibotryon morbosum is its “knot-like” gall structure. These knots can vary in size from anywhere to 13–305 mm (0.5–12 in) long, and up to 51 mm (2 in) wide. This fungus is typically diagnosed by these large black galls at the site of infection.
4 Αυγ 2015 · Damage, symptoms and biology. The name "black knot" aptly describes the most obvious sign of this disease: a rough black gall that can encircle the entire branch. Infection occurs during the spring, but the symptoms do not appear until the following spring.
