Chlorosis

What Is It?
Chlorosis (yellowing) is the term used to describe leaves that are light green or yellow rather than a healthy, dark green. Often, leaf veins remain a darker green while the rest of the blade is lighter. Since this is a non-infectious disease, it cannot be passed from one plant to another. It can be treated, although a seriously affected plant may not respond to treatment and could continue to decline.

What Causes It?
Iron or manganese chlorosis may be caused by high soil pH, compacted soil, poor drainage, root damage, or lack of nutrients in the soil. Chlorosis is often more severe where topsoil has been removed, such as in new housing developments.

What Does It Look Like?
In the early stages the foliage will be lighter green; as it progresses the leaves become yellow with the veins remaining green. Eventually, the foliage becomes dwarfed, may turn rust to orange, appear scorched along the margins, and develop brown spots between the veins. Normally the leaves in the upper most branches, or younger foliage, will be affected first. In addition to pin oak, sweetgum and red maple, other more commonly affected plants include azalea, baldcypress, birch, rhododendron, tuliptree, and blueberry.

How Can I Control It?
The best way to deal with plant chlorosis is to prevent it from occurring. Test your soil pH, and only plant trees and shrubs that can tolerate the existing pH.

To treat plants with existing chlorosis, you have a couple different options:

• Apply sulfur or aluminum sulfate to the soil to increase its acidity (more effective on shrubs than trees).
• Apply iron chelates (pronounced KEY-lates) to the soil.
• Spray foliage with missing nutrients - usually iron or manganese.
• Inject the trunk with missing nutrients.

Foliar Sprays
Use a product like Fertilome’s Liquid Iron for a topical application of iron chelate. The treatment will provide quick, but temporary relief, and will only affect the leaves sprayed. Fertilome’s Liquid Iron contains the micronutrient manganese, a nutrient missing in most maples with cholorsis. Follow the label instructions for using the product as a soil drench treatment.

Soil Treatment
Soil treatment causes no physical damage to the tree itself. Treatment should take place in early spring as the buds begin to swell.

Using a 1 1/2 to 2 inch soil auger, drill 6 to 8 inch deep holes under the tree. Beginning two to four feet from the trunk (on large trees) extend your holes 3 feet beyond the outermost branch tips. Following a grid pattern, space rows 2 feet apart and space the holes 2 to 3 feet apart within each row.

Create a mixture using the Chlorosis Remedy listed below. Apply at the rate of 1 pound per inch of trunk diameter. Water immediately with 1/2 to 1 inch of water.