Iron or manganese chlorosis (interveinal chlorosis) describes a condition in which a tree’s foliage loses its healthy green color and fades to a pale green or yellow hue. This condition, if allowed to progress, will cause slow growth, leaf loss and eventually tree death. Chlorosis is often caused by deficiencies of the micro-elements iron, manganese or zinc and is common to oak, maple, and birch. In alkaline soils, iron and manganese become insoluble and unavailable to the tree. Trees growing in poorly drained soils are also susceptible to iron chlorosis.
Photo provided by ArborjetThe primary symptom is the fading of the leaf color from green to increasingly paler shades of green and, when extreme, to an almost yellow tone. Leaves turn progressively paler green to yellow, with only main veins of the leaf remaining green. Growth is slowed or stunted. As chlorosis continues, the leaf veins turn yellow, and then the leaf dies and falls off. Whole limbs may die back and eventually the death of the tree could occur.
A two-pronged approach to treating chlorosis is recommended.
1) Trunk Injection: By injecting minerals that are deficient in the tree directly into the transport tissue of the tree (xylem), these minerals are available to the tree immediately; thus, it is the fastest way to alleviate symptoms of chlorosis and improve the health of the tree. By rapidly providing the minerals the tree needs, it is able to respond rapidly and generally will have darker, healthier leaves within days or weeks of application. In oaks and birches, inject a formulation that is specially formulated for iron deficiency, such as MIN-jet Iron.
2) Soil Application: Arborjet recommends a supplemental follow up application of ROOT-jet Iron — which can be applied as a soil drench, soil injection or foliar spray — and is formulated to help acidify the soil and provide additional nutrients to aid recovery and long-term health of the tree. The addition of high-quality organic matter to improve soil CEC (cation exchange capacity, a measure of fertility and nutrient retention capacity) and to improve buffer pH (ability of the soil to resist change) is likewise recommended.
(Note: Palm trees with chlorosis can be treated with PALM-jet.)
When to treat
Generally, the best seasons for injection are fall and spring, as uptake occurs when trees are transpiring (moving water through plant matter to release into the atmosphere). The environmental conditions that favor uptake are adequate soil moisture and relatively high humidity. Soil temperature should be above 40 degrees Fahrenheit for trunk injection. Hot weather or dry soil conditions will result in a reduced rate of uptake, so trees should be watered if applications are made when soil is extremely dry. If treating trees in the summer, inject in the morning for the quickest uptake. Tree health will affect treatment efficacy, so assess tree health prior to treating. For example, a declining tree (greater than 50 percent canopy dieback) is a poor candidate for treatment.
For chlorosis, the best time to treat is in the fall, following leaf coloration for foliage responses in the following growing season. When treating in the early spring or summer, use the lowest (micro-injection) label rates. Make applications prior to bud break in spring or, alternatively following leaf maturation (June 15). Always use the lowest label rates when treating birch trees.
What to expect after treatment
Recovery will be proportional to the level of the severity of chlorosis at the time of treatment. Response to treatment can be very rapid; you can expect to see noticeable greening and improved vitality within the growing season and often within weeks of application. Tree responses vary with soil conditions. Calcitic (high calcium content) soils with little organic matter require a comprehensive approach to treatment, including soil amendments.
It is important to be proactive. This means that it is imperative that you treat the disease, not only the symptoms. With the proper assessment and amendment of soil conditions, the tree may not need to be injected again for several years.
Sean Facey is with Arborjet (www.arborjet.com), which develops environmentally responsible trunk injection formulations that protect trees from a variety of insects, diseases and malnutrition. Sean’s interest in trees began in 1982 when he took a job as a tree climber.