Scientists Bruce Wood, Charles Reilly and Andrew Nyczepir at the ARS Southeastern Fruit and Tree Nut Research Laboratory in Byron found that other heavy metals such as zinc, cadmium and copper compete with nickel for uptake channels in the feeder roots of the pecan tree. That may help explain why the researchers found mouse-ear disease in trees growing in nickel-abundant soil.

A severe case of mouse-ear is corrected by a timely foliar application of nickel. The severe form of mouse-ear most commonly occurs in the southern Georgia sector of the U.S. pecan belt, but is also found throughout much of the Gulf Coast Coastal Plain.

Mouse-ear first appears on early spring shoot growth. It can consistently reappear from year to year, or appear only occasionally, on the same trees. Its occurrence is often spotty, and highly variable within affected trees and orchards.

The scientists used two treatment strategies in their studies. In one, they treated foliage in October with nickel sprays. In the other, they treated foliage shortly after bud break in the spring. In both cases, the foliar spray applications of nickel corrected mouse-ear. Fifty trees were treated in the fall, 200 trees in the spring. In every case, nickel sprays corrected mouse-ear.

The Georgia Agricultural Commodity Commission for Pecan, and the Partners in Production granting program of the Southeastern Pecan Growers Association, helped fund the research.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.