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William D. Goff

Triphenyltin hydroxide fungicide sprays were applied at 114, 455, or 910 g·ha-1 either 0, 1, 3, 5, or 10 times during pollination of `Success' pecans [Carya illinoensis (Wangenh.) K. Koch]. Pretreatment flower counts were compared to post-treatment fruit counts 7 and 9 weeks after pollination to determine if chemical rate or application frequency affected fruit set. There were no significant differences among rates, application frequency, or combinations in fruit drop (P > 0.35 in all cases). indicating that spraying this chemical did triphenyltin hydroxide (fentin hydroxide).

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William D. Goff and Gary J. Keever

Container-grown pecan [Carya illinoensis (Wangenh.) C. Koch] trees with “mouse-ear” symptoms, characterized by small, rounded, cupped, and slightly wrinkled leaflets, were repotted into two types of media amended with three rates of dolomitic limestone (0, 5.4, or 10.7 kg·m-3). In both media [4 milled pine bark: 1 sand; 1 soil: 1 peat: 1 perlite (by volume)], mouse-ear symptoms in the season following repotting were dramatically reduced at the lower lime application rates. Medium Fe, Ca, Cu, and Mn and foliar Ca, Mg, Mn, Zn, and B were affected by lime rate 10 months after repotting in one or both media. Medium pH increased quadratically as lime rate increased. Greatest plant recovery occurred when no lime was added, resulting in a pH of 3.9 in the bark-sand medium and 4.2 in the soil-peat-perlite medium.

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Michael W. Smith and William D. Goff

Pecan (Carya illinoinensis) nuts with cracked shells reduce market grade and are usually removed during pecan cleaning. One type of crack is the shell suture that splits on certain cultivars with thin shells and high kernel percentages. ‘Schley’ nuts with diverse kernel moisture concentrations were dislodged from trees on cloudy and sunny days and exposed to ambient environmental conditions for 1 day on the ground. Samples were collected immediately after dislodging and after 1 day’s exposure, sealed in a plastic bag that was placed in a cooler, and then transported to the laboratory where they were assessed for kernel moisture and split sutures. The number of nuts with split sutures was unaffected by kernel moisture percentage or sunlight exposure when samples were collected immediately after dislodging. However, after 1 day, nuts with high kernel moisture percentages with high solar radiant exposure (sunny day) had substantially more nuts with suture splits than those with low solar radiant exposure (cloudy day). At the lowest kernel moisture percentages, the number of nuts with split sutures was insensitive to solar radiant exposure. During the first harvest, ‘Schley’ trees should be shaken to dislodge nuts on cloudy days and harvested before exposure to bright sunshine to minimize suture split. This probably extends to other cultivars with a history of suture split. An alternative to shaking on cloudy days, though not tested, might be to shake trees in the evening and harvest the next morning before exposure to high light conditions. Later, during the harvest season when kernel moisture was lower, sunlight exposure has little, if any, effect on suture splits.

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Michael W. Smith and William D. Goff

Patch budding is a common propagation technique for pecan (Carya illinoinensis) commonly used in the central and western United States, but seldom used in the southeastern United States. Success rates vary, but 75% is normally an acceptable survival rate. Selected budwood and rootstock treatments were evaluated to improve budding success. Additional studies were conducted to evaluate bud forcing techniques that would leave the rootstock intact, allowing a second bud to be inserted if the first patch bud failed. Girdling exceptionally vigorous shoots at the base used for budwood improved success, but neither tip pruning shoots used for budwood or rootstock affected patch bud survival. Patch budding was more successful using budwood from 1-year-old branches than from current season shoots, a finding that greatly extends the window available for propagation using patch buds. The age of rootstock wood at the budding site did not affect patch bud survival. Girdling the rootstock immediately above the dormant patch bud was less effective than top removal for forcing the patch bud in the spring. Application of a lanolin paste of 0% to 5% 2,3,5-triodobenzoic acid (TIBA) or 0.02% 6-benzylaminopurine (BAP) to a girdle immediately above the patch bud was positively related to the percentage of patch buds forcing when tree tops were left intact. The combination of girdling, 5% TIBA, and 0.02% BAP resulted in 76% of the buds forcing compared with 73% forced using top removal. This approach damages trees less and enables a second chance for patch budding on a stronger tree.

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William D. Goff, Monte L. Nesbitt and Cathy L. Browne

Fourteen pecan (Carya illinoensis) clones with desirable traits selected from preliminary screenings were evaluated for scab resistance, foliage condition and foliage retention. No fungicide or insecticide sprays were applied in order to increase pest and disease pressure and to better assess suitability of the selections for low input plantings. Most clones were equal to or better than `Elliott', the resistant standard cultivar and were superior to `Desirable', the susceptible standard cultivar, in scab incidence and foliage condition.

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Monte L. Nesbitt, William D. Goff and Larry A. Stein

Pecan (Carya illinoinensis) cultivars are commercially propagated by grafting and budding. The whip graft, bark graft and four-flap graft, the most frequently used techniques for pecan grafting, require dormant scions, collected and stored for 60 to 120 days before the spring grafting season. Poor graft success is sometimes attributed to poor handling and storage of the scionwood. Moisture content of packing material, sealing cut ends of the scions with wax, and use of polyethylene bags was evaluated in 1998 and 1999. Scions were collected in early February each year, and stored for 60 to 70 days in a household refrigerator at 2 °C (35.6 °F) under different treatment regimes. Scion viability was tested by bark grafting on limbs of mature pecan trees. Moisture of the scions was affected each year by the amount of water added to packing material and by sealing the cut ends, but the differences did not impact graft success. In 1998, graft success rate was equally good among scions stored in polyethylene bags with different amounts of added moisture, whether cut ends were sealed or not. Graft success in 1999 was affected by an interaction of sealing the cut ends, packing material and location of grafting.

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Michael W. Smith, Charles T. Rohla and William D. Goff

Pecan (Carya illinoinensis) leaf elemental concentrations are the industry standard to guide fertility programs. To provide meaningful information, a standard index tissue collected at a specific development stage is required along with established elemental sufficiency ranges. We report pecan leaf elemental sufficiency ranges used in Oklahoma that were developed based on research in Oklahoma and elsewhere. In addition, fertilizer recommendations, based on various leaf elemental concentrations, are included.

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William D. Goff, Michael G. Patterson and Mark S. West

Nutrient status of young pecan [Carya illinoensis (Wangenh.) C. Koch] trees grown under eight combinations of orchard floor management and irrigation was determined by leaf and soil analyses. Orchard floor management practices were weedy-unmowed, weedy-mowed, weed control with herbicides, and weed control by disking, with trees either irrigated or nonirrigated. The element most affected by treatment was K. Mean leaf K for the two sample years was significantly (P < 0.01) lower in the weedy plots (0.56% K) than in those where weeds were controlled (0.76% K), suggesting a highly competitive effect of weeds for K with young pecan trees. Weed competition also suppressed leaf Ca and Mg, but presence of weeds or sod resulted in higher soil pH and higher leaf Zn. Leaf concentrations of N, P, B, Cu, and Fe were not significantly affected by the treatments.

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William D. Goff, Leslie R. Brasher and Mark S. West

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Michael W. Smith, William D. Goff and M. Lenny Wells

The productive life of a pecan [Carya illinoinensis (Wangenh.) K. Koch] orchard frequently spans two or more generations, but eventually orchards require renewal. Weather events damage tree canopies, pests affect tree health and productivity, and new cultivars offer greater yield potential or better nut quality. A popular method of orchard renewal is selective tree removal combined with interplanting new trees. Many old pecan orchards in the southeastern United States are infected with crown gall [Agrobacterium tumefaciens (Smith and Townsend) Conn.], potentially a problem for interplanted trees. Two tree types, nursery-grafted trees and seedling trees that were grafted 3 years after transplanting, were evaluated 6 years after transplanting. Transplanted trees varied in distances from established 80-year-old trees or residual stumps after tree removal. Ten trees near the study site, located 3.6 m from crown gall-infected stumps, were excavated to determine disease incidence. No crown gall was observed on any of the 87 trees in the study or the excavated trees. Trunk diameters of interplanted trees increased as distance from the nearest stump decreased and distance from the nearest established tree increased. Leaf elemental concentrations of the 6-year-old transplants were not related to observed growth differences. Conclusions include 1) stumps promoted rapid transplant growth; 2) crown gall infections of transplanted trees were unlikely even when crown gall symptoms were obvious on adjacent trees and stumps; and 3) transplant growth was suppressed by established trees.