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- Author or Editor: Jeffrey G. Norcini x
The effect of four PGRs on production of `Barbara Karst' bougainvillea [Bougainvillea × buttiana (Bougainvillea glabra Choicy × Bougainvillea peruviana Humb. & Bonpl.) was determined. Liners were transplanted into 3.8-L containers with a soilless substrate on 6 Apr. 1995 and were pruned on 15 May (mean height and width 23.6 and 34.5 cm, respectively). Uniconazole (10 ppm), maleic hydrazide (2808 ppm), daminozide (5000 ppm), and paclobutrazol (50, 100, or 200 ppm) were applied as a foliar spray (to wet) by a compressed air backpack sprayer on 16 May (0 weeks after treatment [WAT]). Daminozide (5000 ppm) was reapplied 31 May and 13 June as described above. Soil drenches of 5, 10, or 20 ppm paclobutrazol were additional treatments. Two nonPGR-treated controls were included: pruned at 0 WAT, and pruned at 0 and 4 WAT. There were eight replications per treatment placed in a randomized complete block design on a container bed under full sun and drip irrigation. At 6, 9, and 12 WAT, growth, flowering, growth habit, number of structural branches (>15 cm long), and level of bacterial spot infection by Pseudomonas andropogonis were recorded. Marketability was recorded 12 WAT and phytotoxicity noted 1, 4, 5, 6, 9, and 12 WAT. No PGR treatment effectively suppressed growth, or enhanced quality or marketability of `Barbara Karst' bougainvillea grown in 3.8-L containers. Furthermore, daminozide reduced the number of structural branches and maleic hydrazide was phytotoxic.
The response of `Barbara Karst' bougainvillea to the chemical pinching agent Off-Shoot-O® (OSO; methyl esters of fatty acids), was evaluated. Liners were transplanted 4 Apr. 1994 into 3.8-liter containers of soilless medium. OSO at 0 (+pruning), 7.8, 15.6, 31.2, 62.5, 125, and 250 ml·liter–1 was applied over the top on 24 May to 20 replications per OSO concentration and 10 replications per control. On 25 May, OSO was reapplied to 10 replications per OSO concentration. Treatments were applied using a compressed-air backpack sprayer that delivered 82 + 3 and 93 ± 2 liter·ha–1 at 2.8 kg·cm–2 on 24 and 25 May, respectively. Crown phytotoxicity was recorded 1, 2, 7, and 13 days after the initial application on a scale of 0 = no injury to 10 = plant death. A growth index and number of stems <5, 5 to <10, 10 to <15, and >15 cm long were recorded 23 May and 7 July. The best overall response was to the 15.6 + 15.6 ml·liter–1 application, despite the slight but commercially acceptable foliar injury (mean rating = 2.3+0.2). This treatment was similar to the pruned control in growth and number of stems.
The response of the root system of `Barbara Karst' bougainvillea [Bougainvillea buttiana (Bougainvillea glabra Choicy × Bougainvillea peruviana Humb. & Bonpl.) `Barbara Karst'] cuttings to 100 g Cu(OH)2·liter-1 in a white latex paint applied to the interior surface of square 66 ml, 120 ml, or 280 ml plastic pots was determined. Cuttings (10 cm long; 3-5 nodes; 2 leaves) were scored on opposite sides and dipped in 6000 mg·liter-1 KIBA for 3 sec. The cuttings were placed in treated or untreated pots that contained a medium of 1 Canadian sphagnum peat: 1 coarse perlite (v/v). The pots were completely randomized in a 3×2 factorial design. The cuttings were rooted under intermittent mist 9 sec·min-1 for 12 hr·day-1 in a greenhouse (20% shade). The number of primary roots, fresh and dry weights, and root quality were determined 15 June. The Cu(OH)2-treated pots resulted in a more compact, well-branched root system and eliminated root circling. However, root fresh weight was reduced by Cu(OH)2 treatment. Pot size influenced the number of primary roots and fresh and dry weights.
The effectiveness of three concentrations of either dikegulac-sodium or mefluidide on the growth of two containerized woody vine crops was investigated. A single application of dikegulac-sodium at 1600, 3200, or 4800 mg·liter-1 or mefluidide at 600, 1200, or 1800 mg·liter-1 was applied to either 3.8-liter containers of Asiatic jasmine (Trachelosoerum asiacticum Siebold and Zucc.) or staked confederate jasmine (Trachelosperum jasminiodes (Lindl.) Lem.) on 25 May 1993. Two additional applications were made at 8 week intervals after transplanting to 9.5-liter containers. Plant growth and phytotoxicity were evaluated 0, 4, and 8, and 1, 2, 4, and 8 weeks after application, respectively. Dikegulac-sodium at 3200 mg·liter-1 was the optimum treatment for suppressing the lateral growth of Asiatic jasmine and the vertical growth of confederate jasmine with minimal phytotoxicity. Dikegulac-sodium at 4800 mg·liter-1 excessively inhibited growth of both species and resulted in unacceptable phytotoxicity. All mafluidide treatments had minimal growth inhibitory effect on either species.
The granular formulation of pendimethalin (Southern Weedgrass Control) safely provides preemergent control of grasses and broadleaf weeds in a variety of landscape ornamentals but few annuals. The purpose of this experiment was to evaluate phytotoxicity of pendimethalin to several annual species under landscape conditions. Pendimethalin at 1.7, 2.2, 2.8, or 3.4 kg ai/ha was applied over-the-top to cool and warm season annuals in a simulated landscape at 4-month intervals starting 15 October 1990. The simulated landscape was divided into 4 blocks (reps) with pendimethalin levels as the main plot factor and annual species as the subplot factor. Unweeded and hand-weeded plots served as controls. Irrigation (over-the-top) and insecticides were applied on an as-needed basis. All annuals except `Sonnet Burgundy' snapdragon exhibited some degree of stunting. `Vodka' wax begonia was the most sensitive to pendimethalin as it was moderately stunted at all rates. Weed control generally was good to excellent.
The parasitic eastern mistletoe, Phoradendron serotinum is a perennial evergreen that infests trees including the deciduous pecan [Carya illinoensis (Wangenh.) C.Koch]. Various chemical and/or mechanical methods of mistletoe eradication have been studied. An efficient method of mistletoe removal in deciduous trees involves the use of ethephon, an ethylene-releasing compound. Mistletoe in dormant `Stuart' trees and `Desirable' trees at bud break were treated on 15 Mar. with 0, 2500, 5000, 7500, or 10,000 ppm ethephon [pH of treatment solution adjusted with 1.2 ml/L of a buffering agent (pH +, Stoller Chemical Co.)]. `Desirable' trees at the prepollination stage of development were treated with 0, 312, 625, 1250, or 2500 ppm + 1.2 ml/L of the buffering agent on 27 Mar. 1991. All ethephon treatments except 312 and 625 ppm resulted in >95% defoliation on 18 Apr. All chemical treatments resulted in abscission cf some mistletoe branchlets. There was a negative correlation between ethephon concentration and mistletoe regrowth on 2 Dec. for both cultivars. The most effective treatment was 2500 ppm applied at prepollination on `Desirable'. This treatment resulted in no mistletoe regrowth on 80% of the trees. No phytotoxicity to the pecans was observed.
Dormancy issues and lack of approved protocols have led to increasing use of the pregermination tetrazolium test to assess whether seeds of premium-priced, prevariety germplasm of native wildflower species are living and have the potential to germinate and develop normally under field conditions, that is, whether seeds are viable. A major concern is the limited amount of industrywide training on how to conduct and interpret results of tetrazolium (TZ) tests for the multitude of native species. Precise methods that yield uniform results are especially critical for testing of prevariety germplasm of native species given their high value and economic consequences of inaccurate test results. In preliminary work, we observed that embryos extracted from intact seeds of native Coreopsis species subjected to TZ testing were viable if they were turgid and appeared normal and were stained pink, red, or were pure white with or without the radicle tip stained pink to red. In this study, we conducted an in-depth analysis of TZ testing of intact seeds of prevariety germplasm of four native Coreopsis species to: 1) verify our preliminary conclusions; and 2) to determine if staining could be improved by preconditioning or gibberellic acid (GA3) because relatively low percentages of embryos of intact seeds stained pink or red. In addition, we evaluated two other methods to assess viability: the excised embryo test and emergence tests in soil and a soilless medium under ambient conditions. We confirmed that embryos extracted from intact seeds subjected to TZ testing were viable provided that embryos were turgid and appeared normal and were stained pink, red, or were pure white ± a pink to red radicle tip. Embryo staining was not consistently improved by moist preconditioning or GA3. Results of pregermination TZ tests of intact seeds and/or germination plus postgermination TZ tests of intact, nongerminated seeds were not consistently accurate and/or uniform across all species and seed lots, issues usually encountered in seed lots that were relatively dormant or of poor quality, and in postgermination TZ testing of seed lots with relatively low dormancy. Moreover, these issues are likely to be encountered even with standard TZ testing protocols given the widely accepted challenges of accurately interpreting TZ tests of native species in general. The most precise, uniform method of assessing viability was the excised embryo germination test because all viable seeds germinated, results were easy to interpret so the likelihood of false-positives or -negatives was nil, and results were very uniform across replications. Emergence tests under ambient conditions substantially underestimated viability. In summary, the high cost of prevariety germplasm seeds of native Coreopsis species, inherent genetic and phenotypic variability, and unknown dormancy characteristics warrant the use of the embryo excision test for determining viability and for increased sample sizes, especially for any tests involving TZ.
Survival of black-eyed susan (Rudbeckia hirta) from three regional seed sources was evaluated after inoculation with the pathogenic fungus Fusarium oxysporum in the greenhouse, and after they were planted in fumigated or nonfumigated and irrigated or nonirrigated field plots. The three seed sources were northern Florida (NFL), central Florida (CFL), or Texas (TEX). Plants from the three seed sources were inoculated individually under greenhouse conditions with four isolates of F. oxysporum originally isolated from the roots of diseased black-eyed susan grown in ecotype trials near Monticello, Fla. About 20% of the inoculated plants developed symptoms similar to those observed in the field, but no consistent ecotype or isolate effects were observed. In the field trial, planting beds were fumigated with methyl-bromide and chloropicrin and irrigated with drip irrigation (high input), not fumigated and irrigated, fumigated and not irrigated, or not fumigated and not irrigated (low input). During the first month of the trial, treatment and seed source had a significant effect on survival due to the low initial survival of NFL in the nonfumigated-nonirrigated plots. After the first month, only seed source had asignificant effect on survival, with TEX decreasing rapidly and the NFL population decreasing to a lesser degree. The decline of TEX could not be directly attributed to pests or climatic effects.
Fresh seeds of prevariety germplasms of goldenmane tickseed (Coreopsis basalis), florida tickseed (Coreopsis floridana), lanceleaf tickseed (Coreopsis lanceolata), and leavenworth's tickseed (Coreopsis leavenworthii) were harvested from cultivated plants and stored under dry conditions for 1 to 24 weeks at 15 or 32 °C to alleviate dormancy, that is, to promote after-ripening. The relative humidity (RH) was 33% for all species except lanceleaf tickseed (23% RH). Seeds were subsequently stored for 24 weeks in a commercial storage facility at 23% RH/17 to 19 °C to determine whether after-ripened seeds could be stored without loss in quality (viability, germination velocity). The only substantial after-ripening occurred with seeds of lanceleaf tickseed, although most after-ripening of lanceleaf tickseed seeds occurred during the 24 weeks of dry storage in the commercial storage facility regardless of storage conditions for the previous 24 weeks. After the 24 weeks in commercial storage, germination of lanceleaf tickseed seeds was 48% to 80%, but germination was only 2% to 15% after 24 weeks of dry storage at 15 or 32 °C, respectively. Freshly harvested seeds of the other three species were much more nondormant than seeds of lanceleaf tickseed, but after-ripening effects were still evident because there were increases in germination or germination velocity (an indicator of after-ripening). Maintenance of seed quality was species-dependent. Seed quality of the two upland species, goldenmane tickseed and lanceleaf tickseed, was maintained during the initial 24 weeks of dry storage plus the subsequent 24 weeks in the commercial storage facility. In contrast, viability of seeds of the two wetland species, florida tickseed and leavenworth's tickseed, declined to varying degrees either during the initial 24 weeks of after-ripening or during storage in the commercial facility. The greatest decline in quality occurred for florida tickseed seeds that were stored for 24 weeks at 32 °C and then for 24 weeks in the commercial storage facility.
Postemergence control of Phyllanthus urinaria L. (chamberbitter) in nursery and landscape plantings has been primarily limited to hand-weeding. Prodiamine was evaluated for postemergence control of chamberbitter and phytotoxicity to containerized ornamentals. On 20 June 1995, prodiamine at 0, 1.68, 3.36, or 6.72 kg a.i./ha was applied over-the-top to immature chamberbitter growing in 3.8-L containers of established Buddleia davidii Franch. `White Bouquet' Cuphea hyssopifolia HBK. `Desert Snow', Lantana camara L. `Irene', and Lantana montevidensis (Spreng.) Briq. `Lavender Weeping'. Weed-free checks were included. Applications were made with a compressed air backpack sprayer. There were four replications per treatment placed in a randomized complete block design by species. Plants were established and maintained on a container bed under full sun and overhead irrigation. Growth of and phytotoxicity to the ornamentals species, and percent coverage and number of chamberbitter, were recorded periodically for 14 weeks after treatment (WAT). Chamberbitter shoots were harvested for dry weight analysis 14 WAT. Prodiamine provided some postemergence control of chamberbitter. However, Cuphea and both Lantana species exhibited leaf distortion and/or delayed flowering.