Leaf Scorch of Trees

Leaf scorch is a physiological disease of plants which occurs when the roots are unable to obtain sufficient water to supply the top of the plant. Leaf scorch occurs when plants are transpiring rapidly during periods of high temperatures with hot, dry winds or during droughts. Any plant may experience this, but symptoms are more commonly seen on broadleaf trees such as maple, ash, elm, chestnut and poplar.

Symptoms are typically most severe toward the top and outer branches. Causes could include:

• Frequent, shallow waterings that cause the soil surface to become compacted and sunbaked, and results in slow death of feeder roots.
• Girdling roots around the trunk.
• Lack of watering after transplanting; recent construction or digging that has killed a portion of the root system.
• Trunk injuries by lawn care equipment.

Multiple years of moisture-induced leaf scorch may cause the tree to show symptoms of dieback in the upper canopy. Suckering along the trunk and large branches are trees’ last resort to survive.

Watering Tips:

• Apply 2 to 3 inches of mulch or well-composted organic matter mulch under trees out to the drip line, keeping it away from the bark.
• Water with a soaking system such as drip or soaker hose for long and deep waterings every week or every other week during drought conditions.
• Water from sprinklers for the lawn is not sufficient.
• Water trees planted in the last 3 years every week, and trees planted up to 6 years ago every other week.
• If you have limited water, focus on your new plantings and woody plants first, garden beds next, and lawns last. 

Scorch due to iron deficiency can often be confused with summer leaf scorch. When this deficiency is the cause of the scorch, addition of a chelated iron compound in addition to irrigation management is the recommended control.

Often times, leaves will begin to show scorch symptoms at the margins followed by interveinal scorching. Younger leaves are usually affected before older leaves.