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Guihong Bi and Carolyn F. Scagel

the spring of 2008 after being sprayed with different combinations of chemical defoliant, urea, and GA in the fall of 2007. Our results indicate copper–EDTA (CuEDTA) can also promote early defoliation of florists’ hydrangeas (control versus copper

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Guihong Bi, Carolyn Scagel, and Leslie Fuchigami

One-year-old field-grown `Nonpareil'/'Nemaguard' and `Nonpareil'/`Lovell' almond nursery trees were used to study the effects of chemical defoliants (CuEDTA and ZnSO4) and foliar applications of urea on defoliation and nitrogen (N) reserves. Although both chemical defoliants significantly promoted earlier defoliation, CuEDTA was more effective than ZnSO4 in promoting early defoliation. Two applications of defoliant had a similar effect as one application on promoting leaf abscission. Foliar applications of urea in addition to defoliant applications (urea + defoliant treatments) generally increased the efficiency of ZnSO4 (1.25% to 2%) and CuEDTA (0.5%) in promoting early defoliation. Although treatments with only defoliants did not consistently lower N reserve levels, trees treated with foliar urea or urea + defoliants had significantly higher nitrogen reserves compared to trees receiving only defoliant treatments. N reserves were comparable in urea + defoliant-treated trees to the levels found in naturally defoliated (control) trees. We conclude that both CuEDTA and ZnSO4 are effective in promoting early defoliation of almond nursery trees. Combining urea with defoliants can effectively promote early defoliation and is important for achieving N reserves similar to naturally defoliated trees.

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Sunghee Guak, Lailiang Cheng, Leslie H. Fuchigami, and Sunghee Guak

Bench-grafted `Fuji'/M.26 trees were sprayed with 1% CuEDTA on 31 Oct., defoliated manually on 12 Nov., or allowed to defoliate naturally. Foliar urea at 3% was applied at 14 days and 9 days before CuEDTA treatment. Plants were harvested after natural leaf fall and stored at 2 °C. One set of the plants were destructively sampled for reserve N (expressed as total Kjeldahl N or soluble protein concentration) analysis, and the remaining plants were transplanted into a N-free medium in the spring without any N supply for 40 days after budbreak. CuEDTA resulted in >80% defoliation within 5 days of application. Trees defoliated with CuEDTA had lower reserve N content than naturally defoliated controls, but had higher N than hand-defoliated controls. Foliar urea application before the CuEDTA treatment significantly increased reserve N level in all tree parts, without affecting the efficacy of CuEDTA on defoliation. The extent of spring regrowth was proportional to the reserve N level of the tree. Urea-treated plants, whether hand- or CuEDTA defoliated, had more growth in the spring than hand- or naturally defoliated controls. It is concluded that CuEDTA, as combined with foliar urea, can be used to effectively defoliate apple nursery trees, and increase reserve N level and improve regrowth performance during establishment.

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S. Laywisadkul, C.F. Scagel, L.H. Fuchigami, and R.G. Linderman

mechanical removal of leaves and the use of chemical sprays [e.g., chelated copper ethylenediaminetetraacetic acid (CuEDTA)] that result in early abscission of leaves, usually while the leaves are still green. Chemical-induced defoliation of deciduous trees

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E.W. Stover, M.J. Fargione, K.A. Iungerman, and W.C. Stiles

Active growth in late Fall 1993, followed by very low temperatures in November, resulted in widespread loss of scaffolds and leaders of `McIntosh' in the Champlain Valley. Treatments to encourage earlier dormancy are being investigated to address this problem in future seasons. Initial studies showed that 39 mm CuEDTA or 16 mm CuEDTA + 0.25% ultrafine spray oil (sprayed to drip) resulted in 3–4 weeks earlier leaf drop of `Empire' in the Mid-Hudson Valley. Evaluation of cold-hardiness, measured as electrolyte leakage after controlled freezing in a Tenney chamber, indicated greater cold-hardiness from these treatments in early December without reducing mid-winter hardiness. CuEDTA treatments ranging from 4–32 mm, all with 0.25% ultrafine spray oil, were applied to fifth leaf `Marshall McIntosh' on M.9/MM.111 interstems in the Champlain Valley on 12 Oct. 1995. Defoliation was accelerated with each increase in rate examined in this study. The highest rate again advanced defoliation 3–4 weeks compared to controls and increased cold-hardiness on 1 Dec. 19/95 as measured though electrolyte leakage. Evaluation of cold-hardiness in shoots collected on 8 Feb. 1996 showed no significant difference between electrolyte leakage from controls and trees treated with CuEDTA.

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D.E. Deyton, C.E. Sams, J.C. Cummins, R.E. Myers, and M.A. Halcomb

Hand-defoliation of field-grown `Golden Delicious' apple and `Bradford' pear nursery trees before autumn digging is a major production cost. One-year-old field-grown trees were sprayed to runoff on 18 Oct. 1994 with; 1) 1% FeEDTA, 2) 1% CuEDTA, 3) 1% ZnEDTA, 4) 100 ppm Harvade, 5) 50 ppm Dropp, 6) 500 ppm Folex, or 7) 2.5% EDTA or 8) leaves were removed by hand or 9) leaves left on trees (control). Treatments were arranged in a randomized complete-block design, with three trees/plot and four replications. Leaves on each tree were counted before treatment and 7, 14, 21, 28, and 35 days after treatment (DAT). One tree per plot was dug, stored until February and grown the following summer. Nontreated apple and pear trees had 13% and 38% defoliation, respectively, 35 DAT. CuEDTA treated apple trees had 62% and 93% defoliation 7 and 14 DAT, respectively. Pear trees treated with Cu had 18% and 100% defoliation 7 and 14 DAT, respectively. Treatment with FeEDTA resulted in 96% defoliation of pear within 7 DAT but only 57% defoliation of apple 35 DAT. ZnEDTA, Harvade, Folex, or Dropp did not significantly promote defoliation. Copper-treated apple trees had less budbreak than nontreated trees but similar budbreak as hand-defoliated trees. None of the treatments influenced budbreak of pear. None of the treatments affected the cumulative dry weight of trees at the end of the next growing season.

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Joseph Albano and Kim Bowman

Nutrient disorders related to excessive levels of copper in soils are common in Florida citrus groves that have been under production for many years, mainly due to the continual use of copper-containing pesticides. The objectives of the study were to investigate the growth and nutritional response of six citrus rootstocks (nonbudded) grown in 4-L containers in sand to increasing concentrations of copper. The rootstocks included: Swingle citrumelo (Citrusparadisi Macf. × Poncirus trifoliata [L.] Raf.), Volkamer lemon (C. volkameriana Ten. and Pasq.), Cleopatra mandarin (Citrusreticulata Blanco), Flying Dragon (P. trifoliata); and two new USDA series rootstocks, US-812 (Sunki mandarin × P. trifoliata released in 2001), and US-897 (a hybrid of Cleopatra × Flying Dragon not yet released). Copper was supplied at 0.05, 0.25, 1.00, and 2.00 mg·L-1 CuEDTA incorporated into a modified Hoagland's nutrient solution. As a mean of all Cu treatments, whole plant Cu levels (μg·g-1) were: Flying Dragon, 17.33; US-897, 21.68; Cleopatra, 27.33; US-812, 28.84; Swingle, 29.74; and Volkamer, 34.05. As a mean of all Cu treatments, foliar Cu levels (μg·g-1) were greatest and least in US-812 (7.74) and Cleopatra (4.05), respectively; and root Cu levels (μg·g-1) were greatest and least in Volkamer (61.08) and Flying Dragon (30.08), respectively.

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Guihong Bi and Carolyn F. Scagel

chelate (CuEDTA) defoliation of apple nursery plants J. Hort. Sci. Biotechnol. 76 35 39 Hoagland, D.R. Arnon, D.I. 1950 The water-culture method for growing plants without soil Calif. Agr. Expt. Sta. Circ. 347

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Viviana P. Sosa-Flores, Luis A. Valdez-Aguilar, Donita L. Cartmill, Andrew D. Cartmill, Adalberto Benavides-Mendoza, and Antonio Juárez-Maldonado

·L −1 ): 4 Fe-EDTA, 2 Mn-EDTA, 0.37 B, 0.32 Zn-EDTA, 0.16 Cu-EDTA, and 0.11 Mo. Plants were manually irrigated when the growing medium registered a moisture tension of 10 cb (Irrometer Model MLT; IRROMETER, Riverside, CA) adding enough solution to attain

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Guihong Bi, Carolyn F. Scagel, and Richard Harkess

urea pretreatment tempers inefficient N recovery resulting from copper chelate (CuEDTA) defoliation of apple nursery plants J. Hort. Sci. Biotechnol. 76 35 39 Hoagland, D.R. Arnon, D.I. 1950 The water