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Web Leaf Scorch
Mary Small
Extension Agent, UIP
Jefferson County
Click on image to enlarge
Leaf scorch is an environmental problem of trees and shrubs. It usually
occurs during periods of hot, dry weather or when hot, dry winds have been
blowing.
Leaf veins remain green and the tissue in between turns brown and brittle.
Leaves turn brown along the outside leaf edges and in between the veins.
Affected leaves may drop or remain attached. Occasionally, leaves on one side of
a tree or shrub show symptoms, while the rest looks normal.
While the immediate cause of leaf scorch is the lack of water, there are many
other reasons scorch symptoms appear. Any factor that damages roots can cause
scorch, since poorly functioning or non-functioning roots can’t absorb water
well. Consider some of these causes of scorch:
- Water is available, but the plant is unable to keep up with water loss
from leaves.
- There is (or has been) too much water in the soil. This drives oxygen out
of the soil, killing roots.
- There is (or has been) insufficient winter water for one or more years.
This damages roots through dehydration.
Other possibilities include:
- Construction activities such as digging, trenching or grade changes
- Compacted soil
- Improper planting including too shallow or deep
- Root competition between trees and turf, perennials or shrubs
- Excessive fertilization
- The addition of excessively deep layers of mulch, plastics or pavement
that restricts or suffocates roots
- Reflected heat and light from buildings and paved surfaces
- Mechanical trunk injuries that restrict the flow of water to leaves
- Diseases that damage branches or trunks and restrict water flow
- Advanced leaf chlorosis
To manage scorch, try to determine the cause of the problem. There may be
several. Try to improve the vigor of the tree throughout the year through proper
pruning, watering, fertilization and pest management. Check soil moisture by
digging a hole 6 to 8 inches deep at the drip line of the plant. Take a
tablespoonful of soil from the bottom of the hole and form it into a ball. If
water runs out when you squeeze it, the soil is too wet. If no water runs out,
gently bounce the ball in your hand a few times. If the ball holds together, the
soil moisture is fine. If the ball comes apart, it is too dry and water is
needed.
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