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Global Forests -
Little Known or Interesting Factoids About Trees and Tree Physiology

Karen Rockoff is the primary contact 
Jim is in the hospital & will take calls through Karen.

Karen Rockoff is the only ISA certified
arborist with 
oakwilt.com.

BEWARE- There are other persons fraudulently representing Oakwilt.com. These persons are not authorized or licensed to use the oakwilt.com name or inject with the chemjet system. Please contact Karen Rockoff immediately if these persons attempt to solicit these services. 

Contact:  Cell: 830.955.0304
                     Karen Rockoff  Arborist  - TDA Certified
email:
klrockoff@yahoo.com
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Iron Chlorosis on Trees


Affected leaves turn a yellowish pale color while the leaf veins remain dark green. In severe cases the leaf color may change from yellow to white or brown.  Iron deficiency or iron chlorosis is the result in a loss of green color and the tree’s inability to absorb the iron it needs, for the production of chlorophyll. Symptoms may appear over the entire tree, one side or limited to individual branches. If iron chlorosis goes untreated twigs and eventually branches may die back leading to mortality of the tree.

Texas soils usually have adequate amounts of mineral iron. However our soils contain usually high amounts of phosphor and potassium and with the high pH (alkalinity), this acts as an iron blocker, changing the iron to  insoluble that trees are unable to absorb.

There are three methods of treatment to provide iron to the trees: Foliar application, soil treatment and trunk implantation.

Foliar Application: If immediate response is needed to correct a chloriotic condition, a foliar Spray with iron sulfate or iron chelate solution should be applied when the tree is in full leaf.  A rate of five pounds of iron sulfate in 100 gallons of water ( approx. 3 oz in three gallons of water) is recommended. Soybean flour may be added to help it adhere to the leaves or you can use a surfactant according to label rates. Iron chelates are water-soluble forms and remain in the solution  when added soil or tree. Always follow the label instructions for determining the proper concentration when applying chelated iron directly to foliage. Is usually best to apply either iron sulfate or iron chelate during the evening or during cool weather periods. A foliar spray produces quick results, or so to say a quick fix, the improvement is temporary because iron will not move into the tree beyond the tissue that was sprayed. New growth will remain chlorotic after the treatment.

Soil Treatment:  Lowering the soil pH is a more permanent way of correcting iron chlorosis. However, it is the most difficult treatment method as it is almost impossible to lower the soil pH sufficiently to depths of 18-24 inches. It is recommended to apply iron sulfate at the rate of 1/2 pound per diameter inch at breast height, and applied to, injection holes under the tree’s canopy on a two foot square grid. Soil injection using chelated iron may also be used at the recommended label rates with liquid or wetable sulfur at equal ratio amounts. This method provides the soluble iron
and the sulfur lowers the pH in small areas and also helps make the existing iron available. 
mixture of equal parts of iron (ferrous) sulfate and sulfur to the soil.
Tree
Diameter
(inches)
Total amount of
Iron sulfate and
sulfur per tree
(pounds)
Number of holes
in ground around
tree
Total amount of equal
parts of ferrous
sulfate and sulfur per
hole (pounds)*
1 1 4 0.25
2 2 8 0.25
3 3 12 0.25
4 6 12 0.5
5 10 20 0.5
6 12 24 0.5
7 14 to 18 19 to 36 0.5 to 0.75
8 16 to 23 21 to 46 0.5 to 0.75
9 18 to 27 24 to 54 0.5 to 0.75
10 20 to 30 27 to 60 0.5 to 0.75
15 30 to 45 40 to 90 0.5 to 0.75
20 40 to 60 53 to 120 0.5 to 0.75

Trunk Implants:  Iron sulfate, or chelate iron in caplets can be implanted directly into the tree trunk, which is released into the trees water transport system to correct iron chlorosis . Implant holes are drilled into the tree and based on the severity of iron deficiency determines the number of implants and also the proper placement is most important to obtain the best results. A normal response occurs in two to three weeks in early spring after the full leaves are out and four to five weeks in summer. Retreatment may not be required for two to three years. The implant wounds are usually small and callous tissue will close the wounds within a year. This is probably the most effect method of treatment and will require regular retreatment in order to maintain a conditional health for the lifetime of your tree. It would be better to avoid tree species that are indigenous to our area and high alkaline soils. 

Iron deficiency is not the only cause of leaf yellowing, other mineral deficiencies such as nitrogen, manganese, boron and zinc may also result in chlorosis symptoms.     

Light applications of ammonium sulfate (21-0-0) with 24% sulfur and micro-nutrients applied three to four times a year will improve the health of the tree. It is important to understand that the alkalinity of the soils is 4 to 5 ft deep and any attempt to correct and lower the soil pH is futile and only a temporary alternative and the pH will ounce back.  

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