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  • Author or Editor: B. W. Wood x
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Pecan [Carya illinoensis (Wang.) Koch] axillary buds of nodal explants from 4- to 12-week-old ‘Stuart’ seedlings were first induced to proliferate shoots and then to elongate on a defined medium. An evaluation of 6-benzylamino purine (BA), isopentenyladenine (2iP), indolebutryric acid (IBA), and indoleactic acid (IAA) for shoot proliferation found a combination of 4 mg/liter BA and 1 mg/liter IBA to be most effective. The synthetic hormones were much more effective at inducing a growth or development response than were their natural counterparts. Gibberellic acid (GA) at 3 mg/liter plus 0.1 mg/liter BA enhanced shoot elongation.

Open Access
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‘Schley’ pecan [Carya illinoensis (Wang.) K. Koch] fruit were selectively thinned within one week after treatment with (2-chloroethyl)phosphonic acid (ethephon) without causing leaf abscission. A concentration range of 25, 50, 75, 100, 150, and 200 ppm caused progressive and selective fruit thinning ranging from 25 to 75%, depending upon concentration and fruit age. Fruit treated when at 4-mm diameter (June 15) were more heavily thinned at the same rate than fruit at 12-mm diameter (July 15). Leaf abscission occurred at rates of 300 ppm or greater on each treatment date. Ethephon levels had no effect on return bloom or fruit set.

Open Access
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Several gibberellin-like substances were detected by cucumber, dwarf pea, and lettuce bioassays after liquid chromatographic (HPLC) fractionation of liquid endosperm from the developing seed of pecan [Carya illinoensis (Wang.) K. Koch cv. Moneymaker]. The response of bioassays to authentic gibberellin standards and fractions eluted from the HPLC column at the same times as gibberellin A3, A4, and A7 suggests that these 3 gibberellins may be present in the liquid endosperm.

Open Access
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Semi-parasitic evergreen mistletoe (Phoradendron flavescens Nutt.) is an increasingly serious weed causing loss of nut yield and tree vigor in pecan [Carya illinoinensis (Wangenh.) K. Koch] orchards of the southeastern United States. Several herbicides and growth regulators were evaluated for efficacy against mistletoe. The dimethylamine salt of 2,4-D proved to be an effective control agent. Ethephon, glyphosate, paraquat dichloride, and polyborate exhibited little or no long-term efficacy. The dimethylamine salt of dicamba also killed mistletoe, but exhibited potential for harming host trees. Dormant season treatment of mistletoe clusters with 2,4-D reduced photosynthesis by about one-third soon after treatment, and by ≈90% from 6 to 16 weeks posttreatment, but clusters did not die until ≈4 months posttreatment. Host limbs, less than ≈3 cm in diameter at the site of mistletoe attachment, usually died within 12 months of 2,4-D treatment of the associated mistletoe cluster. Treatment of entire host trees with 2,4-D did not harm trees if applied prior to ≈1 week of budbreak. Spot treatment of mistletoe clusters, with 2,4-D at 1.2 to 2.4 g·L-1 a.i. (plus 2% crop oil), ≈2 to 3 weeks before budbreak, gave effective long-term control of mistletoe. The inclusion of a crop-oil in the 2,4-D spray greatly increased efficacy. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon).

Free access
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Abstract

Twenty-one days of foliar feeding in late spring by the blackmargined aphid [Monellia caryella (Fitch)] on a mature ‘Stuart’ pecan tree [Carya illinoensis (Wang.) K. Koch] reduced soluble sugars and starch in leaves to 82% and 79%, respectively, of the aphid-free control. Chlorophyll levels were unaffected. Sugars were reduced to 75% of the control in both 1- and 2-year-old branches. Starch in 1-year-old branches was reduced to 71%, but was unchanged in 2-year-old branches.

Open Access
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Abstract

The early-spring mechanical removal of various combinations of buds from one-year-old branches of pecan [Carya illinoensis (Wang.) K. Koch, cv. Desirable] increased the number of lateral shoots and indicated the potential for development of both pistillate and staminate flowers and mature nuts from primary, secondary, and tertiary buds from nodes throughout the length of one-year-old branches. ‘Desirable’ was found to possess strong apical dominance; thus, bud removal and pruning treatments did not greatly increase the development of greater than normal numbers of lateral shoots. Methods that could block apical dominance and allow continued development of young shoots that normally abort appear to have potential of greatly increasing crop productivity.

Open Access
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Abstract

Pecan [Carya illinoensis (Wangenh.) Koch] kernel development is characterized by rapid accumulation of dilute acid and dilute alkali soluble proteins and decline of buffer and alcohol soluble proteins during embryo and cotyledon expansion. Mature kernels contained 7.8% protein, consisting of 51% acidic glutelins, 27% alkali glutelins, 9% concentration alkali, 7% prolamine, 4% albumin, and 1% globulin. Each fraction was composed of at least 2 proteins throughout kernel development. Proteins in each fraction were comprised primarily of neutral amino acids, but individual amino acid levels were highest for basic amino acids, with relatively high levels of lysine and sulfur containing amino acids. Electrophoresis of acid soluble glutelins revealed at least 7 subunits with molecular weights of 102, 58, 37, 30, 26, 19, and 16 (x 103). The data are considered in relation to alternate bearing and manipulations of fruit maturity.

Open Access
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Abstract

Eight of 9 insecticides used for pest control in pecan [Carya illionoensis (Wang.) K. Koch] suppressed net photosynthesis (Pn) of mature leaves in the orchard after a single spray treatment. Reductions were on the order of about 20% of pretreatment levels within 1 day after treatment. Sprays continued to suppress Pn for several days after application. Leaves exhibited no visible damage as a result of spray treatments. Emulsifiable concentrate formulations tended to be more detrimental to Pn than were wettable powder formulations. Four applications of fen valerate and carbaryl at 14-day intervals suppressed Pn by about 20% for the duration of the 55- day treatment period. Thus, repeated applications did not influence leaves in an additive or synergistic manner, and leaves did not adapt and become insensitive to the insecticide sprays.

Open Access

Zonate leaf spot (ZLS) [Cristulariella moricola (Hino) Redhead (C. pyramidalis Waterman and Marshall)] on pecan [Carya illinoinensis (Wangenh.) K. Koch.]—associated with unusually wet weather during June, July, and August—occurred across much of Georgia during Summer 1994. Scott–Knott cluster analysis indicated that 27 of 36 evaluated genotypes exhibited little or no field susceptibility to ZLS. `Moneymaker' exhibited the greatest susceptibility of all cultivars studied, with `Cape Fear', `Elliott', `Sumner', and `Sioux' segregating to exhibit moderate susceptibility. An evaluation of commercial orchards indicated susceptibility of major southeastern cultivars as `Desirable' < `Stuart' < `Schley' < `Moneymaker'. Control of ZLS in commercial orchards using standard fungicide spray strategies appeared to be generally ineffective.

Free access

Fungal leaf scorch, a potentially devastating disease in pecan [Carya illinoinensis (Wangenh.) K. Koch] orchards, was influenced substantially by irrigation and genotype. Three years of evaluating 76 pecan cultivars revealed that all cultivars exhibited scorch symptoms and that at least three classes of scorch susceptibility existed. Severity of symptoms was also much greater in nonirrigated than irrigated trees, and there were substantial differences in the concentrations of free nitrogenous compounds and free sugars in leaves between irrigated and nonirrigated trees.

Free access