Landscape
And
Nursery
Dialog
Mary Ann Rose
Commercial Landscape
& Nursery Specialist
The Ohio State UniversityJuly, 1995
Micronutrient deficiencies in trees
Keywords: micronutrients, tree health, nutrition, fertilizers, landscape
M icronutrient deficiencies can become painfully obvious in mature trees in the mid- to late summer in many parts of Ohio. This problem often appears in the foliage as an intervenal chlorosis in mature specimens of red maple, pin oak, and other species, and as a general yellowing of foliage in white pine and ericaceous plants. Severely affected plants also exhibit dieback. This condition is difficult to correct because it usually arises from an incompatibility between the mature tree and a high-pH soil. The required nutrients are often present in the soil, but at higher soil pH levels (6.5 and above) trees are incapable of taking up adequate amounts. Unfortunately, modifying the pH of the root environment of a sizable tree is not a practical solution.
Steps to take. Iron deficiency is the most common deficiency problem on ornamental plants, but manganese and zinc deficiencies may occur as well. Foliar analysis can be helpful in diagnosing micronutrient problems, but soil analysis may be limited in its usefulness since the elements are often present in the soil but unavailable. Micronutrient deficiencies also may be diagnosed by spraying solutions of iron, manganese, and zinc sulfate (1 1/2 tablespoons per gallon of water) on separate branches of an affected tree, and observing whether any of the treatments reverse the chlorosis.
Foliar sprays may be useful for diagnosis, but are usually not practical to correct the problem in a large tree. Usually deficiencies in mature trees are corrected by soil application or trunk injection of sulfated or chelated micronutrients. Broadcast applications of liquid or dry fertilizers may be made under the trees; however, to avoid spoiling turf, the micronutrients may be applied to holes drilled around the circumference of the dripline, about three feet apart. Liquid, chelated micronutrients seem to correct problems more rapidly than sulfated microelements.
Trunk injection is another method that has gained acceptance, and in some cases may be easier and faster-acting than soil applications. Medicap capsules and the Mauget systemic injector units are both available to landscape professionals; Medicaps are available to homeowners. These trunk injection products should be implanted in the early spring when the sap begins to flow. They are less effective if implanted after leaves unfold. If possible, position the drill holes for these products in the root flare of the tree; there is evidence that better distribution throughout the tree results. Disease entry to the wound will be limited by drilling the hole no larger than necessary. Place the hole vertically on the sides of the root flare to prevent water draining into the hole.
Medi-ject is another commercial injection system that may be used later in the season to relieve deficiency symptoms. Compared to Medicaps and the Mauget injection system, a much greater volume of solution is injected into the tree with the Medi-ject product,.
The prognosis. Severe chlorosis and decline of mature trees are rarely reversible. The treatments discussed here are useful for cases of moderate deficiency, and usually must be repeated yearly or every few years.
