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.
