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Introduction
Leaf scorch is a physiological problem that can occur on any kind
of plant. It can be caused by transplanting, soil compaction, nearby
excavation, a nutrient deficiency, chemical injury, unfavorable weather
conditions (such as drought), poor soil, or limited room for root
growth. Scorch often occurs in July and August, especially on newly
planted trees, when the roots cannot supply enough water to offset
the water lost through the leaves in transpiration. Hot, dry winds
will increase the amount and severity of leaf scorch, especially in
the early summer after a cool, wet period.
Symptoms
Symptoms of leaf scorch include yellowing and/or darkening
of tissues between the main leaf veins or along the leaf margins,
sometimes with dark angular spots in the discolored areas. Entire
leaves may become brown and wither when leaf scorch is severe. Plants
affected by leaf scorch may lose many leaves during late summer and
exhibit some twig dieback. However, they often recover if the cause
of stress on the plant is not chronic.
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Figure 1: Symptoms at leaf margin.
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Management Strategies
Sometimes severely affected plants may be fertilized and watered
to help overcome leaf scorch. Apply fertilizer in the spring and
by broadcasting over the ground under the spread of the branches
at the rate suggested on the label directions. Proper watering
by saturating the soil to a depth of six inches is especially
important. Water once every one to two weeks during dry periods.
Light, general pruning of trees and shrubs helps reduce the total
foliage load that must be supported by the root system. Dead and
dying branches should also be removed. All pruning tools should
be disinfected by dipping them in alcohol or 10% bleach (1 part
bleach in 9 parts water) after each cut. Pruning wounds should
be coated with shellac if invasion by canker-causing fungi and
bacteria is likely to occur.
If the cause of leaf scorch is chemical injury by salt toxicity,
fertilizer burn, weed killer injury, etc., recovery may be slow.
In some cases, leaf scorch is the first sign of irreparable chemical
injury that may result in the plant's death. If salt toxicity
or fertilizer burn are suspected, where possible, leach the soil
by slowly trickling water onto the soil for 24-48 hours. Deicing
salt toxicity may be prevented in some cases by building a curb
or drainage ditch that carries the spring snow melt away from
plants' root zones.
Created, KLS, 8/99
This publication contains pesticide recommendations.
Changes in pesticide regulations occur constantly, some
materials mentioned may no longer be available, and some
uses may no longer be legal. All pesticides distributed,
sold, and/or applied in New York State must be registered
with the New York State Department of Environmental
Conservation (DEC). Questions concerning the legality and/or
registration status for pesticide use in New York State
should be directed to the appropriate Cornell Cooperative
Extension Specialist or your regional DEC office. READ
THE LABEL BEFORE APPLYING ANY PESTICIDE.
__________________________________________________________________________________
The Plant Disease Diagnostic Clinic
at Cornell University is located at 334 Plant Science Building,
Ithaca, NY, 14853. Phone: 607-255-7850, Fax: 607-255-4471,
Email: kls13@cornell.edu
or slj2@cornell.edu
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