Mouse-ear (ME) is a severe growth disorder affecting pecan [Carya illinoinensis (Wangenh.) K. Koch] trees from southeastern U.S. Gulf Coast Coastal Plain orchards. Slight to moderate ME was substantially corrected by foliar sprays of either Cu or GA3 shortly after budbreak, but sprays were ineffective for severely mouse-eared trees. Applications of Cu, S, and P to the soil surface of moderately affected trees corrected deficiencies after three years. Incorporation of Cu or P in backfill soils of newly planted trees prevented ME, whereas incorporation of Zn or Ca induced ME and Mn was benign. The severe form of ME, commonly exhibited by young trees, appears to be linked to a physiological deficiency of Cu and/or Ni at the time of budbreak. It likely occurs as a replant problem in second-generation orchards due to accumulation of soil Zn from decades of foliar Zn applications to correct Zn deficiency.
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