Leaf Scorch
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Identification
- Browning of leaf margins
- Yellowing or darkening of tissue between the main leaf veins
- Entire leaves may dry out, turn brown and become brittle
- Leaves sometimes wilt rapidly, usually remaining a pale green color even when dried out
- May lose leaves prematurely during late summer and exhibit some twig dieback
- Often more pronounced on exposed leaves, or upper, southern or windward side of trees
- If moisture supply to roots is adequate, new leaves will often form where older leaves have dried up
Often Confused With
Fire blight (pears) – shepherd’s crook with dead leaves remaining attached; bacteria ooze from affected tissues during periods of high humidity or rain
Biology
Leaf scorch is caused by failure of the tree to supply enough water to the leaves at a critical time, usually in late summer. Leaves transpire rapidly during periods of high temperatures with hot, dry winds or during droughts. If the water supply is deficient, the exposed leaves dry out and scorch.
Newly planted trees are particularly subject to leaf scorch as the roots cannot supply enough water to offset the water lost through transpiration. Leaf scorch symptoms may also appear following damage or disease in the roots or injury to the trunk. As well, symptoms can be caused by many adverse environmental conditions, including soil compaction, nutrient deficiency (nitrogen, magnesium, potassium), drought, salt toxicity and herbicide injury.
Period of Activity
Hot, dry winds will increase the amount and severity of leaf scorch, especially in the early summer after a cool, wet period. However, more commonly, during July and August, when water or heat stress is highest, scorched leaves begin to turn brown at the margins. Premature leaf drop may occur in late summer.
Scouting Notes
Where hot, drying winds occur for several days during the period of active tree growth, more severe scorch symptoms may appear. Leaf scorch symptoms may also appear following damage or disease in the roots, injury to the trunk, or following excessive salt or herbicide application.
Look for damage on the upper portion on the southern or windward side of the tree.
Management Notes
Plant in a protected area with fertile, well-drained soil and an adequate supply of organic matter.
Sometimes young or severely affected trees may be fertilized and watered to help overcome leaf scorch.
Light, general pruning of trees help reduce the total foliage load that must be supported by the root system. Dead and dying branches should also be removed.
If the cause of leaf scorch is chemical injury by salt toxicity, over-fertilization or herbicide injury, recovery may be slow. Where possible, leach the soil by slowly trickling water onto the soil for 24-48 hours.
Some information included above excerpted from;
