Preparation for next year’s fruit crop can begin this fall by spraying trees for several fruit tree diseases. Bacterial canker, bacterial spot, coryneum blight and leaf curl are diseases that can be slowed by spraying now.
Bacterial canker is the most serious of the targeted diseases. It is a common cause of tree dieback and death. Canker also causes bleeding or gumming along the trunk and branches. In eight out of 10 cases, fruit tree gumming is caused by canker rather than borers, which are often mistakenly blamed for the problem. Canker gumming is especially evident in the fall. It is caused by a systemic bacteria that plugs the tree’s vascular system. The only thing that will help trees seriously infected with canker is good care: adequate water, fertilizer and weed control.
Bacterial spot and coryneum blight commonly damage leaves and sometimes the fruit of stone fruit trees in the spring and summer. Physical signs of these diseases are leaves with small holes; in severe cases, trees are defoliated. Spraying now will not eliminate the disease but will reduce its incidence next spring and summer.
Another common disease is leaf curl, which causes extremely crinkled leaves in the spring. Leaf curl is caused by a fungus that quits once temperatures begin to get warmer. The disease is worse following a cool, damp March, but spraying now is usually sufficient to prevent it from becoming bad enough to cause heavy defoliation next spring.
Spraying different mixtures of Kocide 101, Kocide 606 and Kocide DF or any multi purpose fungicides containing copper can be used effectively to prevent these diseases. Kocide 101 is the only formulation available in small enough qualities to be practical for garden use. Kocide does contains copper, which will cause leaf burn on healthy green foliage, so wait until the leaves are beginning to drop and are easily brushed from the tree. It is best to apply this spray while most of the leaves are still attached, but the spray is worthwhile, even if most of the leaves have already dropped.
Besides spraying, sanitation is important in reducing the carryover of disease to next year’s crop. Mummified and rotting apples, dead wood on the ground or in the tree, plus ragged stubs of broken branches harbor disease spores. These items should be pruned out, gathered and burned or tilled into the soil.
Fall is not a good time to prune fruit trees or other deciduous plants. Pruning stress, especially when coupled with other stresses including drought, poor nutrition and disease, can make the tree more vulnerable to winter injury.
Due to recent rains, soil moisture levels across much of Wise County seem adequate to carry fruit trees and vines as they enter dormancy. However, don’t let the recent rains fool you. Remember even though we have had some rain we are still right in the middle of a record drought. The roots of deciduous trees, vines and shrubs are active throughout the fall and winter, and the soil should never be allowed to dry.