Leaf Scorch

The hot, dry days of July are more than a discomfort to many shade trees. Leaf scorch, a non-infectious disease is becoming more prevalent with each hot day.

Leaf scorch is first noticed as a yellowing or bronzing of tissue between the veins or along the margins of leaves.

Trees are more susceptible if they have low vigor, have been damaged by machinery or are surrounded by cement sidewalks or driveways.

Symptoms usually follow drying winds or bright sunlight. Later, these leaves appear dry and scorched and may even drop off. However, the tree itself will not die.

In most cases, all leaves on the same branch are affected more or less uniformly. Frequently, only one side of the tree is affected – the side exposed to the sun or drying winds. Occasionally, individual trees are severely damaged, while those of the same species in the immediate vicinity are unaffected.

Leaf scorch is caused by failure of the tree to supply enough water to the leaves at a critical time, usually in July and August. A great amount of water evaporates from the leaf surface because of sun and wind during hot, dry weather. If the water supply is deficient, the exposed leaves actually dry out and scorch.

Trees with defective root systems are particularly subject to leaf scorch. The same holds true for trees whose roots have been partly removed or covered with impervious material like asphalt or concrete paving.

Soil that drains excessively or that has a low water table as well as attacks by leaf-sucking insects can also contribute to the scorch problem.

Leaf scorch cannot be corrected once it appears, but injury can be kept to a minimum by improving the tree’s general condition.

If the tree has a permanently suppressed or injured root system, prune some of the branches to maintain an even balance between top and roots. This practice will not injure the tree and may actually improve its appearance.

In the spring, apply fertilizer.

For prized trees, mulch to improve the soil’s water-holding capacity and water liberally to the sub-surface during hot weather.

If the root system has been injured by excavation, you can expect leaf scorch to recur during drought until the tree repairs the damage or produces a new root system.

Source: David Robson, Horticulture Educator, University of Illniois

Mid-Summer 1998
Five Steps to Healthier Grass in Shady Spots | Tree Tips for Buyers of New Homes | Summer Tree and Shrub Watering Care | Leaf Scorch | Spraying Facts for the Garden | Bug Bites—Grubs | Lawn Care Calendar | Cybergarden Sites | Hort Shorts | Hort Tips | Food Handling: What to Do with Food During a Power Outage | In the Kitchen: Friendship Cake | Food Safety: How to Make A Friendship Cake Starter | Locally Grown: At the Farmers' Market | Health and Household Tips

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