Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2003
Publication Date: 2/1/2004
Citation: Wood, B.W., Reilly, C.C., Nyczepir, A.P. 2004. Mouse-ear of pecan: II. Influence of nutrient applications. HortScience. 39(1):95-100. Interpretive Summary: Pecan farmers in the southeastern U.S. often suffer economic losses associated with a replant problem termed Mouse-ear. The problem was determined to be most likely due to temporary deficiency of Cu at bud break. The replant characteristic is due to suppression of Cu uptake by decades of accumulation of Zn annually applied to pre-existing trees. This information allows for modification in orchard management strategies that correct existing problems as well as how to avoid future Mouse-ear problems.
Technical Abstract: Mouse-ear(ME) is a severe growth disorder affecting pecan [Carya illinoinensis (Wangenh.) K. Koch] trees in orchards within the Gulf Coast Coastal Plain of the southeastern U.S. Slight to moderate ME was corrected by foliar sprays of either Cu, Mn, or GA3 shortly after budbreak, but sprays were ineffective for severely MEed trees. Applications of Cu, S, and P to the soil surface of moderately affected trees corrected deficiencies after 3 years. Incorporation of Cu and P in backfill soils of newly planted trees prevented ME whereas Zn and Ca induced ME and Mn had no effect. An evaluation of soil characteristics of orchards with ME vs. adjacent orchards without ME indicated that the most severely affected orchards typically possess high amounts of soil Zn, Ca, Mg, and P, but low Cu and Ni; and are acidic and sandy textured. The Zn:Cu ratio of soils appears to be a major factor contributing to symptoms, plus the severity of ME increases as the Zn:Cu ratio increases. The severe form of ME, commonly exhibited by young trees, appears to be primarily due to a physiological deficiency of Cu, and likely occurs as a replant problem in second-generation orchards due to soil accumulation of Zn after decades of foliar Zn applications to correct Zn deficiency.