Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/5/2003
Publication Date: 2/1/2004
Citation: Wood, B.W., Reilly, C.C., Nyczepir, A.P. 2004. Mouse-ear of pecan: I. symptomology and occurrence. Hortscience. 39(1):87-94. Interpretive Summary: Pecan farmers in the southeastern U.S. often suffer economic losses associated with a problem termed Mouse-ear. The problem was determined to be largely a replant problem. Study of Mouse-ear symptomology indicates that the disorder is likely due to a physiological deficiency of copper at the time of bud break. This information provides a basis for the development of control strategies that can prevent or correct yield losses due to Mouse-ear in southeastern orchard operations.
Technical Abstract: Mouse-ear is a potentially severe anomalous growth disorder affecting young pecan [Carya illinoinensis (Wangenh.) K. Koch] trees in portions of the Gulf Coast Coastal Plain of the southeastern U.S. A survey of its incidence and severity found it to be commonly exhibited by replants on second-generation orchard sites, or where mature pecan trees previously grew. While most frequently observed as a replant problem, it also occasionally occurs at sites where pecan has not previously grown. The disorder is not graft transmissible and is only temporarily mitigated by pruning. Degree of severity within the tree canopy typically increases with canopy height. Several morphological and physiological symptoms are described beyond that previously reported for mouse-ear. Particularly notable symptoms include dwarfing of all tree organs, poorly developed root systems, rosetting, delayed bud break, loss of apical dominance, reduced photo assimilation, nutrient element imbalance in foliage, and increased water stress. The collective symptomology is consistent with a physiological deficiency of a key micro nutrient at bud break, that is subject to influence by biotic (such as nematodes) and abiotic (orchard water and fertility management strategies) factors. It is hypothesized that the severe form of mouse-ear is primarily due to a physiological deficiency of Cu at the time of bud break.