Mouse-Ear Can Be Defeated

By Sharon Durham
November 22, 2004

Pecan growers battling a tree ailment called "mouse-ear" can now rest assured that help is on the way, thanks in part to Agricultural Research Service scientists who discovered that the condition is caused by a nickel deficiency in the plant.

The ARS discovery has led to a commercial fertilizer application to control mouse-ear. This growth and development abnormality, recognized as "little-leaf" in other crops, is becoming increasingly common in second-generation pecan orchards where new trees are planted.

Nickel deficiency was pinpointed as the problem by research leader Bruce Wood and plant pathologists Charles Reilly and Andrew Nyczepir at ARS' Southeastern Fruit and Tree Nut Research Laboratory in Byron, Ga.

A foliar fertilizer, called NICKEL PLUS, has been developed by NIPAN, LLC, of Valdosta, Ga. It has been approved by the Georgia Department of Agriculture as a fertilizer nutrient that can correct nickel deficiency problems in pecan and river birch trees. Wood assisted with determining the treatment formulation, which will be available for distribution next spring.

Wood and his colleagues saw there was a lack of nickel uptake by the plants even if there was an abundance of nickel in the soil. Heavy metals such as zinc, manganese, iron, cadmium and copper compete with nickel for uptake channels in the feeder roots of the pecan tree. Additionally, lighter metals such as magnesium also act to indirectly limit nickel uptake. It was found that nickel deficiency had usually been induced by excessive accumulation of other elements due to decades of fertilizer applications.

The severe form of mouse-ear most commonly occurs in the southeastern Georgia sector of the U.S. pecan belt, but is also found throughout much of the Gulf Coast Coastal Plain.

The anomaly first appears on the spring flush of shoots. A severe case of mouse-ear is corrected by a timely foliar application of nickel.

ARS is the USDA's chief scientific research agency.