A maximum rate of 10 pounds of iron chelate per 1000 square feet of soil can be used. Lower doses should be sufficient in neutral or slightly alkaline soils. Injection sites or holes should be 2 to feet apart and 1 to 6 inches deep. Apply equal portions of liquid or dry material to these sites in the feeder-root zone beneath the canopy drip line. Best results are obtained from treatments made in April, May or June.
Treatments usually remain effective for several years.
Implantation or injection of iron directly into the trunk of pin oaks is being done with some success. This method, often used by commercial arborists, may be effective for a few months to 1 year. Girdling Roots Tree roots normally grow outward in a radius from the trunk. When a lateral root intertwines with another main lateral root or encircles the trunk, a girdling root problem can occur. Gradually, one or more of the aboveground symptoms of shade tree decline become evident.