Chlorosis Diagnostic Guide
Chlorosis is a serious issue of shade trees where the plant is unable to properly manufacture chlorophyll. Chlorophyll is an important leaf component which is responsible for energy absorption for the entire tree. Trees without enough chlorophyll will not be able to grow and live. If this condition is not corrected, the tree will eventually die. The causes of chlorosis are complex and not entirely understood. As a general rule, it is caused by the lack of a micro-nutrient or a combination of micro-nutrients that a tree needs to manufacture chlorophyll. Iron and manganese are the common micro-nutrient deficiencies that cause chlorosis in shade trees. These minerals are often not lacking in the soil, rather a condition exists where the tree’s root system is unable to obtain them in usable forms.
Trees at Risk
All shade trees are susceptible to chlorosis, but some species are more commonly affected than others. These include pin oak, willow oak, white oak, red maple, silver maple, river birch, sweetgum, catalpa, aspen, camphor, white pine, Japanese black pine, magnolia, azalea, and rhododendron.
Signs of Damage
- Yellowing in between veins on newer foliage.
- Brown discolored areas developing on chlorotic leaves.
- Tip dieback and decline on severely affected trees.
- Chlorotic trees will often show symptoms where the color of the tree is light green, yellow, reddish and, in severe cases, white.
- Iron and manganese deficiencies often develop in the newer growth first.
- Trees that are severely affected may exhibit tip dieback and decline and become more susceptible to other pest and abiotic stresses.
Verdur™ is intended to be used as part of a broader management plan for treating chlorosis. The practitioner must address the underlying factors that cause chlorosis in the overall management strategy. While applications of Verdur™ may cause a green-up for several years, consider other treatments like decompaction, and practices that stimulate root development.
Tree Injection using Verdur
Notes: HIGH RATE Dosage: 1 pkt of Verdur will treat 2 in DBH. Mix the Verdur pkt with 1/2 gal of water for every 10 in DBH. Timing: Treat in late summer just prior to the development of significant fall color. Do not use High Rate in the spring. Re-Treatment: Every three years
Tree Injection using Verdur
Notes: LOW RATE Dosage: 1 pkt of Verdur will treat 6 in DBH. Mix the Verdur pkt with 1/2 gal of water for every 10 in DBH. Timing: Treat after full leaf development during the growing season. Follow up with High Rate in the late fall. Re-Treatment: Annually
- The dosage rates listed above have been optimized for oaks and birch. Additional species can be treated, but applicators should treat small scale numbers of trees first to determine specific application rates for different species under actual use conditions. Efficacy may vary depending on weather conditions, geographic conditions, and other factors.
- A single application of Verdur™ at the HIGH rate will provide up to 3 growing seasons of chlorosis suppression (green-up).
- Color improvement may be seen as soon as 2-3 weeks after treatment with Verdur™.
- Do not treat trees in rapid decline.
- Some maple species have shown inconsistent responses to Verdur™, and results are not as predictable on maples as on oaks and birch.
- Using the HIGH rate during the growing season can result in significant phytotoxicity and early leaf drop.
- Verdur™ is a recovery treatment and is only the first step in the treatment of chlorosis:
- Include additional cultural practices and products to promote tree health and to create a more suitable growing environment.
- Consider Cambistat® applications to stimulate root growth and development.
A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org