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 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.
Treatment Strategy
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 pH adjustment of soil, decompaction, and practices that stimulate root development.
Other Treatment Practices
- Cultural practices to improve root health are often employed in chlorosis management including:
- Application of a TGR (Cambistat) to improve root system and increase chlorophyll production*
- Air-spading or vertical mulching to alleviate compaction
- Mulching over root zone
- Eliminating competing vegetation such as turf grass
- Rainbow’s Root Enhancement Protocol
- Prescription fertilizer applications
- Applications of soil applied micronutrients may provide an additional source of Iron or Manganese
Tree Injection Using Verdur Mn
Tree Injection Using Verdur
Soil Application Using Cambistat
Expected Results
A single application of Verdur Mn will provide up to 2 growing seasons of chlorosis suppression (green-up). Using the higher rate in late summer may provide longer residual than spring application. Color improvement with Mn treatments does not occur as rapidly as what is noted with Verdur injections on oak and birch. Responses typically occur in the next subsequent growing season. The response of maples to Verdur Mn is generally not as consistent as the response noted with Verdur on oaks and birch.
A single application of Verdur 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. Some maple species have shown inconsistent responses to Verdur and is not as predictable on maples as it is on oaks and birch. Using the HIGH rate during the growing can result in significant phytotoxicity and early leaf drop.
Signs of Damage
Since chlorophyll is what causes the tree to be green, chlorotic trees will often show symptoms where the color of the tree is light green, yellow, reddish and in severe cases white. Manganese (Mn) and iron (Fe) are often difficult to distinguish from each other without foliar chemical analysis. Some researchers suggest the fine veins in the leaves will become chlorotic with Mn deficiency while they remain green on Fe deficient trees. In practice, this is difficult to determine in the field, so most Mn and Fe deficiencies are diagnosed by commonly affected species (maples more frequently have Mn deficiency, whereas birch and oak have Fe deficiency). Both Fe and Mn 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 insect, fungal, and abiotic stresses.
- Yellowing in between veins on newer foliage
- Necrotic areas developing on chlorotic leaves
- Tip dieback and decline on severely affected trees
Photo: Joseph O’Brien, USDA Forest Service, Bugwood.org
Photo: Joseph O’Brien, USDA Forest Service, Bugwood.org
Trees At Risk
All shade trees are susceptible to chlorosis, but some species are more commonly affected than others. Species commonly affected by Fe deficiencies include:
- White oak
- Silver maple
- River birch
- Sweetgum
- Catalpa
- Aspen
- Camphor
- White pine
- Japanese black pine
- Magnolia
- Azalea
- Rhododendron
Species commonly affected by Mn deficiencies include:
- Numerous maple species
- Birch
- Dogwood
- Flowering cherry
- Sweetgum
- Sargeant crab apples
Always refer to product label for rates and approved uses. Some images courtesy of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments.
