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  • Author or Editor: William Goff x
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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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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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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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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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Growth of pecan (Carya illinoensis (Wangenh.) C. Koch `Melrose') and pear (Pyrus calleryana Decne. `Bradford') trees in the nursery was greater in containers designed to hold water in the lower portion. The water-holding reservoir was obtained either by placing 76 liter containers in a frame holding water to a depth of 5 cm, or by using containers with drainage holes 5 cm above the bottom. The continuous waterlogging at the bottom of the containers resulted in root pruning and root death in the lower portion of the containers, but roots grew well above the constantly-wetted zone. Fresh weight of tops, caliper, and plant height were all greater after two growing seasons in the containers with water reservoirs compared to similar containers with no water reservoirs.

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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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Pecan [Carya illinoensis (Wangenh.) C. Koch] trees were grown in containers in a pine bark and sand medium amended with O, 3.0, 5.9, 8.9, or 11.9 kg dolomitic limestone/m. Mouse-ear symptom expression, characterized by small, rounded, cupped, and slightly wrinkled leaflets, increased linearly as dolomitic lime rate increased. Plant growth was best at 3.0 kg dolomitic lime/m, which resulted in a growth medium pH of 4.3.

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Pecan is a difficult species to propagate by grafting. The whip graft, bark graft, and four-flap graft, the most often-used techniques for pecan grafting, require dormant scions, collected and stored for 60 to 120 days prior to spring-season grafting. Poor graft success is often blamed on handling and storage environment of the scionwood. Moisture content of packing material, waxing of cut ends, and use of polyethylene bags was evaluated in a controlled experiment in 1998 and 1999. Scions were cut in early February each year, and stored for 60 to 70 days in a household refrigerator under different treatment regimes. Scion viability was tested by bark grafting mature pecan trees in Fairhope, Ala., and Uvalde, Texas. In 1998, graft success rate was equally good among scions stored in polyethylene bags with different amounts of added moisture, whether cut ends were waxed or not. Moisture loss of the scions during storage was affected each year by the amount of water added to packing material and by waxing the cut-ends, but the differences did not impact graft success. An interaction of not waxing the cut ends and very wet packing material reduced graft success at Fairhope, Ala., but not Uvalde, Texas, in 1999.

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