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Yuqing Wang, Richard J. Heerema, James L. Walworth, Barry Dungan, Dawn VanLeeuwen, and F. Omar Holguin

Pecan is the only major tree nut crop native to North America ( Grauke and Thompson, 2008 ). Native American tribes consumed and traded pecans long before the arrival of European explorers to the continent, but interest in cultivating pecans as a

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Wheeler G. Foshee III, Eugene K. Blythe, William D. Goff, Wilson H. Faircloth, and Michael G. Patterson

Weed competition can reduce growth ( Patterson et al., 1990 ; Smith et al., 2002 ; Wolf and Smith, 1999 ), yield ( Foshee et al., 1997 ; Patterson and Goff, 1994 ), and nut quality ( Daniell, 1974 ) of pecan trees. This reduction in growth has

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Lenny Wells

The profit potential of pecan increased in 2009 with sudden growth in the Asian pecan export market. As a result, there has been a renewed interest in the crop, which has led to the planting of additional pecan acreage throughout the United States

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Bruce W. Wood, Larry. J. Grauke, and Jerry A. Payne

An assessment of vegetative traits of pecan [Carya illinoinensis (Wangenh.) K. Koch] from a range-wide provenance collection indicated the existence of at least two distinct populations within the native range (i.e., provenances north of Texas vs. provenances in Texas and Mexico). Southern most provenances generally broke bud earlier, retained foliage later in the fall, grew larger in height and trunk diameter, had narrower leaflet droop angles, had greater leaflet tilt angles, wider limb angles, greater Zn deficiency, less black pecan aphid susceptibility, and less red coloration to foliage than did northern most provenances. Trees originating from Jaumaua, in northern Mexico, were especially noteworthy insomuch that they were by far the tallest, possessed the largest trunk diameters, the longest foliation period, and lowest Zn deficiency ratings of all provenances. One family within this Jaumaua population also exhibited a high level of cold hardiness. Family heritability (hf 2) estimates were ≥0.48 for trunk cross sectional area, date of budbreak, leaf redness, cold injury, leaflet droop angle, and leaflet tilt angle, and ≤0.39 for late season leaf fall, black pecan aphid susceptibility, zinc deficiency, and branch angle.

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Yahia Othman, Dawn VanLeeuwen, Richard Heerema, and Rolston St. Hilaire

precipitation is 200 mm and average annual temperature is 20 °C. Pecan is one of the most important agricultural crops in New Mexico. In 2012, New Mexico produced 31.3 million kilograms of pecan nuts (in-shell basis), which accounted for ≈23% of the U

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Geno A. Picchioni, Sharon A. Martinez, John G. Mexal, and Dawn M. VanLeeuwen

use of hardwood chips. In Fall 2012, we completed a pilot study at two nearby commercial greenhouse and nursery production sites using various rates of pecan wood chips in the substrate, prepared as described below for the present investigation. A

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Michael W. Smith, Becky S. Cheary, and B. Scott Landgraf

A low leaf Mn concentration was detected in bearing pecan (Carya illinoinensis Wangenh. C. Koch) trees growing in an alluvial soil with an alkaline pH. Trees lacked vigor and leaves were pale in color, but there was no discernible leaf chlorosis or necrosis. Three foliar applications of MnSO4 beginning at budbreak, then twice more at 3-week intervals at rates of 0 to 3.3 kg·ha-1 of Mn increased leaf Mn concentration curvilinearly, and alleviated leaf symptoms. Results indicated that three foliar applications of MnSO4 at 2.15 kg·ha-1 of Mn plus a surfactant were adequate to correct the deficiency.

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Bruce W. Wood, Charles C. Reilly, Ted Cottrell, W. Louis Tedders, and Ida Yates

The influence of pecan [Carya illinoinensis (Wangenh.) K. Koch] leaflet bronzing, a discoloration of the lower surface, on foliar physiology and nut-meat yield is unknown. Field investigations indicate that bronzing can adversely affect foliage by reducing net photoassimilation (A), stomatal conductance (sgw), and transpiration (E) while also altering stomatal aperture and cellular structure, and increasing temperature. Kernel weight and fill percentage are also reduced. Research indicated that foliar A declined in proportion to degree of bronze coloration, with negative A exhibited by heavily bronzed foliage. A by bronzed foliage did not increase as light levels exceeded ≈250 μmol·m-2·s-1. Within the same compound leaf, nonbronzed leaflets adjacent to bronzed leaflets exhibited greater than normal A. Bronzed leaflets also exhibited lower sgw to water vapor, less transpirational H2O loss, and higher afternoon leaf temperature. Light micrographs of bronzed foliage indicated abnormal epidermal and spongy mesophyll cells. Weight and percentage of kernel comprising the nut declined on shoots supporting foliage bronzing in July to August, but was unaffected when bronzing occurred in September to October. Bronzing of pecan foliage can therefore be of both physiological and economic significance.

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Marvin Stokes, Tom Harlan, Marvin Harris, and J. Benton Storey

Analyses of stem cross sections of 97 pecan [Carya illinoinensis (Wangenh.) K. Koch] and 22 post oak (Quercus stellata Wangenh.) trees from seven sites showed tree rings were sensitive to the environment and were datable by tree, among trees within a site, among sites, and between species. Pecan had well-defined annual growth rings averaging from 1.25 to 3.36 mm in width and that varied synchronously among trees. Pecan had a mean sensitivity of about 0.3 compared to 0.4 for post oak, indicating a smaller but adequate response of pecan to reflect climatic variations and to use pecan tree rings in other dendrological studies.

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Eric T. Stafne, Charles T. Rohla, and Becky L. Carroll

with pre-emergent herbicides provided no cover for voles and resulted in no tree loss. A secondary issue is nutmeat fragments left in pecan shells used for mulch that may support toxigenic fungi. In one study, Penicillium charlesii was found to be