What Causes Bitter Pear Rot?
Few things are as delightful as a fresh, ripe pear. Spots on pears may be a symptom of bitter rot, a disease of apples, pears, peach, quince, and cherry. Various conditions affect the development of the disease including temperature, tree health, site, and soil. Bitter rot on pear affects only the fruit and generally occurs during the hottest periods of the growing season. There are several cultural and hygienic steps you can take to prevent pears with bitter rot. The causal agent is a fungus, Colletotrichum gloeosporioides (syn. Glomerella cingulata). It overwinters in fruit mummies, cracked bark, dead plant material, and cankers. The spores are spread by birds, rain splash, wind, and possibly insects. The disease really gets going when conditions are rainy and temperatures are 80 to 90 degrees F. (27-32 C.). When hot, muggy weather occurs late in the season, an epidemic of the fungus may occur. In orchards the disease can spread rapidly from tree to tree, causing huge economic loss. It only affects fruit, although occasionally some cankers will form on tree bark.
Symptoms of Bitter Rot on Pear
Symptoms are generally observed in late summer. The fungus is one of the few that can penetrate the skin of the fruit without an entry wound. The first signs are small, round brown spots on fruit. If temperature and humidity are high, the spots rapidly enlarge. Once the spots become ¼ inch (6 mm.), they begin to sink in and have a saucer shape. Once the spots are ½ inch (1 cm.), the fruiting bodies appear. These are tiny black spots in the rotting center of the spot. Pears with bitter rot then begin to ooze a pink, gelatinous substance that leaks and soaks down onto lower dependent fruits. The fruit will continue to decay and eventually shrink into a mummy.
How to Prevent Bitter Pear Rot
The first steps to avoiding fungal spots on pears is to clean up the area after the harvest period. Remove any mummies on the ground and those clinging to the tree. If there are wounds to the tree, treat them with fungicide or cut damaged limbs back to healthy material. Remove any pruned wood from the area. Provide good care including fertilizer, water, and pruning to encourage healthy growth and a vigorous tree. During the growing season, apply a fungicide every 10 to 14 days to manage the disease. In organic situations, good sanitary practices and care are the best preventatives.
