Part 3 - Caring for Apple Trees in Central Florida
Last week we discussed pollination, cultivation, fertilization, and irrigation. Today we will end with training and pruning and pest control.
Training and pruning:
Young apple trees should be trained to a modified central leader system. On two year-old-trees, five six strong scaffold limbs should be selected to develop a strong framework. These limbs should have wide angles almost perpendicular to the trunk of the tree, should be radially spaced around the tree trunk and vertically spaced approximately 6" to 8" from each other up and down the trunk.
Harvesting and Storage:
Apples ripen satisfactorily on the tree. They should be picked when they have reached optimum size and color. Slightly immature fruit will also ripen with satisfactory quality in a refrigerator. If fruit diseases increases with summer rainfall it may be advisable to harvest them slightly before optimum harvest maturity. Fruit of Anna, Dorset Golden have been stored satisfactorily in refrigeration for six to eight weeks.
Preventive control of pest is required to maintain healthy trees producing good fruit quality. Some of the problems are:
- Apple scab: This fungus, caused by venturia ineaqualis, affects leaves, flowers and fruit. Lesions develop on both leaf surfaces causing leaf distortion. Scabby, dark-spots are clearly seen on infested fruit. As fruit matures in regions having a warm climate, the spot commonly appears as russeted scars. Previous infection of immature fruit results in cracking and distortion of the area associated with scab lesions.
- Fireblight: This bacterial disease, induced by Erwinia amylovora, spreads from tree to tree primarily during bloom. Fireblight is normally only a severe problem during a prolonged cool period in the spring. Typically, shoot tips become blackened, and appear as if they have been burned. It can generally be controlled by reducing nitrogen fertilizer which results in over vigorous growth. When infection is present, the infected area should be pruned out, cutting at least 8" to 10" below the lowest visible infection. The pruned-off limbs then should be burned.
- Botryosphaeria canker: This fungal disease is caused by Botrysosphaeria dothidea is by far the most debilitating disease of apple trees in Florida. Twig cankers first appear as water- soaked spots that eventually enlarge and produce rings of black fruiting structures. It can spread from twigs to scaffold limbs and eventually to the trunk.
- Bitter rot: This fungal disease, incited by Glominella cinqulata, infects the fruit, but causes stem cankers. Bitter rot on the fruit starts as a small, circular light brown area. Spots enlarge rapidly and become darken.
- Mushroom rot: this fungal disease incited by armillaria tabescens, attacks the roots and can result in tree death.
- Scale insects: Several scale insects, primarily San Jose Scale, may infest leaves, twigs, branches or fruit and is usually controlled by a 2-35 dormant oil application.
- Rabbit Control: Rabbits eat the bark of apple trees and can kill the tree trunk. For best control, a physical barrier such as hardware cloth or plastic tree guards should be placed around the trunk of the tree. Rabbits will also feed on pruning in preference to young trees.