QuestionI live in SE Texas (Houston area). I have an oak in my backyard(8" trunk at the base) whose leaves this year came in yellow with green veins. My search on the internet leads me to believe this is iron chlorosis. I called a local tree service with a very good reputation and they say that it is a fungus and a lot is around this year. I've treated with Ironite, but with very limited results. I also can't find where "fungus" is associated with iron chlorosis. Is the tree service correct? Their fix is deep root chemicals.
Thanks for the help.
AnswerWhen the tissue between the veins turn yellow, it is iron deficiency. The most common cause of iron deficiency is high (alkaline) soil pH. When soil pH exceeds 6.5 to 7.0 the availability of iron in the soil is greatly reduced. Other causes of iron deficiency include lack of iron in the soil, excess soil moisture or root rot diseases.
Initial symptoms of iron deficiency are a yellowing or chlorosis between the veins of younger leaves. The veins usually remain green. In more severe cases, inter veinal and marginal browning or necrosis occurs. This is followed by premature leaf drop and dieback of twigs and branches. Fungal leaf spots are more common on leaves with iron deficiency and may tend to make the necrosis appear worse.
Add iron to the soil in sufficient quantity to increase the amount available to tree roots. In bare soils, iron sulfate can be applied to the ground under the tree canopy at a rate of one pound per half inch of trunk diameter measured 4?feet above the ground. Trees growing in turf-covered soil should be deep-fed either by liquid injection with a hydraulic sprayer or by iron sulfate placed in holes drilled into the soil.
Drill holes spaced two feet apart and 15 to 18 inches deep should form concentric circles around the tree, beginning two to three feet from the trunk and extending beyond the ends of the branches about three feet.. This treatment remains effective for two to three years. Chelated iron may be used, but be sure to follow label directions for rates. Best results for the current year will occur when treatment is made in early spring just as buds begin to swell. Also, high pH soils may prevent most iron chelates from working. For any soil with a pH above 7.2, use an iron chelate with EDDHA. Such products include Sequestar 6%, Sprint 138 and Millers FerriPlus.
Iron deficiency is not the only cause of leaf yellowing. Herbicide damage or other mineral deficiencies such as nitrogen, manganese, boron or zinc may also result in chlorosis symptoms. Signs of manganese deficiency, in particular, may be similar to those of iron deficiency. The two can be distinguished by the broad bands of normal green color that remain next to the major veins if manganese is lacking. Leaves on the ends of the branches of manganese-deficient trees generally are not affected until late in the summer after growth has stopped.
I would also call the Texas Forest Service office in your county and ask one of their Foresters to come take a look. They have a Insect and disease forester and an urban Forester either should be able to help advise you.
Here is the web link to the Houston County contact page.
http://texasforestservice.tamu.edu/main/article.aspx?ctrl=14
