Iron Chlorosis in Trees

When iron in the soil is either trees, iron chlorosis causes the leaf After the soil is mixed in the bucket, deficient or unavailable to trees, iron veins to remain green while the area about one pint of soil is needed for chlorosis can occur. In most Kansas between the veins is yellow-green to testing. Soil or leaf samples can be soils, iron is plentiful, but unavail- yellow. Leaves that emerge in early taken to the local extension office or able to trees. Iron is readily available spring are frequently of normal size. sent to other laboratories. to trees growing in soils with a pH Leaves emerging later in the year of 5.0 to 6.5. In soils with a pH are often smaller and more yellow. Correcting Iron Chlorosis of 7.0 (neutral) and above, iron In severe cases, the leaf color may Once iron chlorosis or soil with changes to an insoluble form that is change from yellow to white and a high pH is confirmed, several not as available to trees. finally brown. In advanced stages, treatment methods can provide Several species of ornamental twig dieback may be observed, iron to the tree. These include foliar and native trees in Kansas suffer especially toward the top of the tree application, soil amendment, trunk from iron chlorosis. The most and ends of the branches. After injection, and trunk implantation. susceptible species are pin oak, silver several years, the tree may die if the Foliar application. If a rapid maple, baldcypress, and sweetgum. condition is not treated. response is needed, a foliar spray White pine, river birch, walnut, Variations in the soil, especially with iron sulfate or iron chelate sugar maple, red maple, eastern in urban areas, may result in iron solution may be applied to the redcedar, sycamore, ornamental pear, chlorosis symptoms appearing on leaves when the tree is in full leaf. and some crabapple species may one side of the tree or on individual A rate of 5 pounds iron sulfate in develop iron chlorosis. Treating iron branches. In some cases, trees that 100 gallons of water (2.5 ounces chlorosis can be expensive. There- have excessive amounts of moisture iron sulfate in three gallons water) fore, proper selection of trees that or are growing in an area with poor is recommended. Soybean flour (1 tolerate soils with a high pH and are drainage may look chlorotic. tablespoon per gallon) or detergent less effected by low iron availability (one teaspoon per gallon) may be is the best preventative for iron Diagnosis added to the solution to help the chlorosis. Soil testing and leaf sampling iron sulfate adhere to the leaves. should be done before treating a tree Iron chelates are water-soluble Symptoms for iron chlorosis, especially with forms of iron that remain in the Iron plays a major role in tree species other than pin oak. Soil solution once added to the tree. producing chlorophyll, the green testing can determine soil pH and Follow label instructions for pigment in leaves. A deficiency of other nutrients available to the tree. determining the proper concentra- iron reduces the amount of chlo- Soil samples should be taken about tion when applying chelated iron rophyll the leaves produce. When 6 to 8 inches below the surface of directly to foliage. When applying chlorophyll is reduced, a yellowing the ground. Several samples should either iron sulfate or iron chelate, of leaves occurs. This is an early be taken in random locations, then applications made in the evening sign of iron chlorosis. On deciduous mixed together in a clean bucket. or during periods of cool weather

Kansas Forest Service are recommended. A foliar spray produces quick results. However, the improvement is temporary because the treatment will only affect the leaves sprayed. New growth emerging after the treatment may be chlorotic. Soil treatment. Lowering the soil pH is a more permanent way of correcting iron chlorosis caused by soils with a high pH (above 7.0). Unfortunately, this method is one of the most difficult treat- ments. One procedure is to add soil amendments such as sulfur, iron sulfate, or aluminum sulfate Drip Line to the soil. Sufficient quantities are needed to acidify soil and increase the amount of iron available to the 4 1/2 (DBH) tree. Iron sulfate can be applied to 2-3' bare soil under the tree canopy. The application should be spread under the tree canopy to beyond the drip line (see diagram). The applications can be applied in conjunction with 2' 2' core cultivation to incorporate the treatment into the soil. The recom- mended rate is 1 pound per inch of per inch in tree diameter are recom- inch of trunk diameter. The recom- tree diameter. Tree diameter can be mended. The root systems of trees mended rate for trees greater than attained by measuring the circum- often grow well beyond the drip 4 inches in diameter is a mixture of ference of the tree at 4 feet above line. Therefore, holes or injection 2 to 3 pounds of iron sulfate/sulfur the ground then dividing by 3.14. sites placed past the drip line are mixture per inch of trunk diameter. The best method for treating recommended. This treatment These mixtures should be applied trees growing in turf-covered soil remains effective for 2 to 3 years. as described above. Some available is liquid injection with a pressure Chelated iron may be used, but products are packaged with iron applicator or placing iron sulfate in be sure to follow label directions for and sulfur combinations. If these holes drilled or punched into the rates. For best results, the treatment products are used, be sure to follow soil. Holes or injection sites spaced should be made in early spring, just all label instructions. 2 feet apart and 6 to 10 inches deep as buds begin to swell. If holes are Iron tablets also are available can form a grid pattern under the drilled or punched into the soil, for application into the root zone tree (see diagram), beginning 2 to 3 make sure there are no underground beneath the tree. The tablets feet from the trunk and extending utility lines in the area. have a quick release iron complex beyond the ends of the branches An alternative soil treatment bound with a dispersing agent. (drip line). If holes or soil injections is the mixing of sulfur to the iron Some tablets also contain sulfur. are made, calculate the treatment sulfate at a 1:1 ratio. The sulfur Obtaining even distribution of the amount based on the product lowers the pH in a small area to iron in the root zone is sometimes label and divide the treatment by make the iron more available to difficult, and some branches may the number of sites. Place equal the tree. The recommended rate remain chlorotic. The tablets should amounts of the treatment at each for trees 4 inches and smaller is 1 be distributed in the soil as specified site. In general, four to five holes pound of iron sulfate/sulfur mix per on the label. Trunk injection systems. The Mauget microinjection wounds will take longer to close. If system consists of a capsule of iron trunk injection or implants are used, and implantation chelate or iron ammonium citrate the homeowner should investigate Iron sulfate, iron ammonium injected into the tree trunk through the feasibility of other treatments citrate, or iron chelate injected or a needlelike tube. The capsule is described to avoid repeated implanted directly into the tree pressurized by compressing before wounding of the tree trunk. trunk is an effective method for attaching to the tube. Small holes greening up iron-chlorotic trees. A are drilled near the base of the response is normally seen within Other Causes of Yellowing trunk or root flares of the tree to fit two to three weeks if applied in Iron deficiency is not the only the tubes. The Medi-Ject system the spring after leaves are fully cause of leaf yellowing. Brown leaves contains a network of plastic tubing developed. Trees treated later in the that appear to show a severe case and T’s placed in drilled holes summer may not show a response of iron deficiency may be caused around the tree trunk. Gravity is until the following year. Additional by leaf scorch or another problem. used to feed an iron sulfate solution treatments will vary depending on Herbicide damage or other mineral directly into the trunk. the severity of chlorosis, tree species, deficiency– such as nitrogen, manga- All injection systems have been and individual tree response. In most nese, boron, or zinc – also may result field-tested and found effective cases, additional treatments may not in chlorosis symptoms. Signs of under specific conditions. Results be needed for 3 to 5 years. manganese deficiency, in particular, will vary with tree species, severity of Some trunk injection systems and can appear similar to those of iron chlorosis, time of year, soil mois- implants can be applied by home- deficiency. Manganese deficiency ture, and individual tree response. owners, and others must be applied can be distinguished by the broad Following label directions, especially by professionals. The most common bands of normal green color that for rates and time of year for each treatments available to homeowners remain next to the major veins. treatment, should give the desired include products such as Medicaps. Leaves on the ends of the branches results. Medicaps consist of a plastic capsule of manganese-deficient trees gener- filled with an iron citrate. Implant ally are not affected until late in the holes are drilled in the tree trunk Trunk Wounding summer after growth has stopped. where the capsule is to be placed. Some authorities have expressed Usually a foliar application of the When implanted in the tree trunk, concern over the number of wounds deficient mineral in the summer, will the capsules release the iron citrate required with trunk injection result in a temporary green-up of into the water transport system of and trunk implantation methods. the leaves. If the foliar application of the tree. Capsule spacing is based Whenever holes are drilled into the mineral thought to be deficient on the diameter of the tree. Proper trees, damage to live tissue occurs. does not cause a temporary correc- placement is important to obtain These wounds can provide entry tion, this is a good indication that desired results. Follow all label points for disease organisms. The another mineral deficiency is causing instructions when using the capsules. size of wounds will vary between the problem. Other possible causes Trunk injection and implant each treatment. If the wounds are should be investigated. systems available to commercial small, callous tissue will usually close arborists include Mauget, Medi‑Ject, the wounds within one year. Larger Nutri Booster, and gravity-fed Dennis W. Carlson District Forester, South Central

• Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. This publication is made available in • Publications from Kansas State University are available at: www.ksre.ksu.edu cooperation with the USDA Forest • Contents of this publication may be freely reproduced for educational purposes. All other Service. USDA is an equal opportunity rights reserved. In each case, credit Dennis W. Carlson, Iron Chlorosis, Kansas State University, provider, employer, and lender. September 2003.

Kansas State University Agricultural Experiment Station and Cooperative Extension Service MF718 September 2003 It is the policy of Kansas State University Agricultural Experiment Station and Cooperative Extension Service that all persons shall have equal opportunity and access to its educational programs, services, activities, and materials without regard to race, color, religion, national origin, sex, age or disability. Kansas State University is an equal opportunity organization. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, as amended. Kansas State University, County Extension Councils, Extension Districts, and United States Department of Agriculture Cooperating, Marc A. Johnson, Director.