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  • Author or Editor: W. Witte x
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Interior surfaces of tube trays were painted with white exterior acrylic latex paint and white interior latex paint containing 0, 50, or 300 gm/1 copper sulfate. Germinated Quercus acutissima seedlings were used to study chemical root pruning effects and subsequent root regeneration. After 16 weeks, only 0.73 roots per seedling continued growth after being deflected by the tubewall painted with 100gm/1 compared with 3.67 for the control. Fibrous roots were reduced when in contact with cu treated surfaces. Height and caliper were not affected at any treatment level. Three weeks after transplanting to larger untreated containers, height and caliper were still unaffected by any cu treatment. Time required for regeneration of new roots was not affected by cu treatments.

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Previous research at this facility has shown that copper sulfate, when incorporated with latex paint and applied to the interior surfaces of tube trays, was effective in chemically root pruning Quercus acutissima seedlings. Only 20% of deflected roots continued to grow after contacting Cu treated tube walls compared to controls. Treated plants showed a reduction of fibrous roots on the plug surface. Height and caliper were not affected by Cu treatments during chemical root pruning in the tube tray. Time required for regeneration of new roots was not affected by Cu treatments. Seedlings from each treatment were planted and grown two seasons under field conditions to observe effects on growth and root regeneration. No treatment effects occurred for height or caliper. Oak seedlings chemically root pruned with Cu exhibited more lateral growth and branching than control plants.

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The root system of containerized nursery stock may become undesirably coiled or matted on the outer surface of the media. Various copper formulations painted on the interior of the container surface have been shown to control undesirable root growth in a few species. We tested a commercial formulation of 100 g/l copper hydroxide in a flowable latex paint formulation (SpinOut™) on 41 tree, shrub, and herbaceous species. Plants were grown 4 months in 7.5×7.5×15cm containers, either treated or untreated. Root density was evaluated on a scale of 1 to 5 (no roots on the surface to heavy rooting). Analysis showed treated containers prevented roots from growing on the media surface in all species tested except Magnolia liliiflora `Jane', Buxus sempervirens `Vardar Valley', and Taxus × media `Hicksii', where control of surface rooting was significant but moderate. Copper paint did not inhibit growth of stolons or rhizomes, which morphologically are stem structures. No visual signs of copper toxicity were observed, nor were there any differences in shoot growth.

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Cut rose (Rosa hybrida L.) flowers placed in water often wilt prematurely, which is partially due to bacterial accumulation in the stems. Bacterial strains in the stems are mainly pseudomonads and enterobacteria. The possible sources of these organisms were investigated in `Sweet Promise' (trade name Sonia) roses. No bacteria were found in the xylem of intact plants. Cutting the stems with sterile secateurs introduced no bacteria at the cut surface or the stem interior, but cutting with nonsterile secateurs used by rose growers did. The secateurs sampled at rose growers contained Enterobacter agglomerans along with several other bacteria not found inside the xylem of cut flowers but did not contain pseudomonads. Although the plant surface may contain bacteria, freshly cut stems placed in water introduced no bacteria. Bacteria rapidly developed on the cut surface and inside the water-conducting elements when rose stems were placed in tap water, even when the stems had been surface-sterilized. However, there were no bacteria in vase water when the water and the stem surface had been sterilized. Since the stem and the secateurs are not a main source of bacteria inside stems and tap water contains pseudomonads and Enterobacter spp., we conclude that tap water is the main source of the bacteria inside cut rose stems.

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Abstract

Flowering plants of several cultivars of poinsettia, Euphorbia pulcherrima Willd, were placed in darkness or low intensity artificial light to determine their influence on induction or retardation of abscission of leaves and bracts.

Photoperiod was not a factor in abscission control but abscission of leaves and bracts was induced in darkness. Light of 25 or more ft-c intensity had an effect in delaying abscission. Longer light periods were more effective and continuous 25 ft-c light was as effective in delaying abscission as 8 hr of 225 ft-c light. Continuous 225 ft-c light delayed abscission for periods up to 60 days.

Leaves tended to abscise before bracts in darkness and bracts before leaves in low intensity light. Higher light intensities were required to delay abscission following longer dark periods than following shorter or no dark storage. Leaf and bract abscission were promoted by 11 days of darkness and delayed by 75 ft-c light in cv. ‘Elisabeth Ecke’ while the long lasting cv. ‘New Ecke White’ required 16 days for promotion of leaf abscission (bract abscission was not promoted by 16 days of darkness) and 25 ft-c light was capable of delaying abscission.

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Powdery mildew (Microsphaera pulchra) of flowering dogwood (Cornus florida L.) has become a significant problem of trees in nursery production as well as in the landscapes and forests of the eastern United States. The disease significantly reduces growth and berry production by older established trees and may contribute to the inability of younger trees (liners) in production to survive winter dormancy. Disease resistance in named cultivars is limited to partial resistance found in `Cherokee Brave'—all other cultivars are extremely susceptible. Until now, the only disease control measure was to establish an expensive, labor-intensive, preventive fungicide program. We examined >22,000 seedlings and identified 20 that were extremely resistant to powdery mildew. Three trees with white bracts were selected from the 20 and released as patent-pending cultivars. `Karen's Appalachian Blush' has long, non-overlapping, pink fringed bracts with a delicate appearance. `Kay's Appalachian Mist' has creamy white, slightly overlapping bracts with deeply pigmented clefts. `Jean's Appalachian Snow' has large, strongly overlapping bracts with non-pigmented clefts. The three powdery mildew-resistant cultivars will be entered into an existing breeding program with `Appalachian Spring', a cultivar released by the Tennessee Agriculture Experiment Station and resistant to dogwood anthracnose, in an attempt to produce trees that are resistant to both diseases.

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Commercially available Acer rubrum and A. freemanii taxa were established as 10 single-plant replications in a cultivar trial at the TSU–NCRS in 1992 and Spring 1993. Plants were fertilized regularly and drip-irrigated as needed beginning Summer 1993. Growth data were recorded each fall and height and caliper increment calculated for the 1994 season. Ten cultivars were in the group with most height growth: `Armstrong', `Autumn Blaze', `Schlesingeri', `Olson', `Morgan', `Scarlet Red', `Embers', `Indian Summer', `Scarsen', and `October Glory'. These all differed significantly from a group of 11 slow-growing cultivars. With some exceptions, cultivars with the most height growth tended to have the most caliper growth, while those with the least height growth tended to have the least caliper growth. Data will also be presented on insect and disease ratings.

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Eighty-one accessions of oak species, hybrids, and cultivars from commercially available sources were established at TSU-NCRS in Fall 1993 and Spring 1994, using 10 single-plant replications in a randomized complete block. Drip irrigation was begun on a regular basis May 1994, and plants were fertilized regularly. Height and diameter was recorded Fall 1994 and 1995. Fastest growing oaks in order of cm height growth increment over the two growing seasons were nigra, phellos, texana nuttalli, cerris, macrocarpa, falcata pagodaefolia, macrocarpa `Maximus', acutissima, austrina, shumardii, muehlenbergi, falcata, robur fastigiata, lyrata, virginiana, palustris, acutissima `Gobbler', glandulifera, macrocarpa `Ashworth', gambelli ×macrocarpa, alba. Most evergeen oaks did not survive Winter 1995–96, and data will be reported on winterkill.

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Research was conducted to compare non-ionic, paraffin-based crop oil, soybean oil, sunflower oil, and organosilicone surfactants combined with Manage (MON 12051, holosulfuron) applied at a reduced rate for yellow nutsedge (Cyperus esculentus) control efficiency and evaluation of phytotoxicity to five container-grown ornamental species. Manage at 0.018 kg a.i./ha was combined with 0.25% or 0.5% (v/v) of the following surfactants: X-77, Scoil, Action “99”, Sun It II, or Agri-Dex. Yellow nutsedge tubers (10 per 3.8-L container) were planted into containers along with the following nursery crops: `Lynnwood Gold' forsythia, `Big Blue' liriope, `Pink Lady' weigela, `Blue Girl' Chinese holly, and `Bennett's Compacta' Japanese holly. Treatments were applied 5 weeks after potting on 13 June 1998 and phytotoxicity ratings taken 4 and 8 weeks later and growth measured after 8 weeks. Sun It II provided the most-effective nutsedge control without reducing growth and causing minimal phytotoxicity to the ornamental plants tested. X-77 (the recommended surfactant for Manage) provided only moderate nutsedge control. Efficient nutsedge control can be accomplished with Manage at one-half the recommended rate when combined with the correct surfactant. Some temporary phytotoxicity symptoms can be expected and a slight overall growth reduction is possible, depending on the surfactant selected.

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