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J.G. Norcini and J.H. Aldrich

Eight species of low-growing woody and herbaceous landscape plants were evaluated for tolerance to 1.1 or 2.2 kg a.i. bentazon/ha (plus a crop oil) applied over the top twice 7 days apart. Raphiolepis indica L. Lindl. `Alba' was the only species tolerant to bentazon in either of two experiments. Bentazon injury to Liriope muscari (Decne.) L.H. Bailey `Evergreen Giant' was minor (slight chlorosis) and would probably be tolerable under most landscape situations. Injury (primarily chlorosis/necrosis) to Carissa macrocarpa `Emerald Blanket', Juniperus horizontalis Moench `Bar Harbor', Pittosporum tobira (Thunb.) Ait. `Compacta Green', Trachelospermum asiaticum (Sie-bold & Zucc.) Nakai `Aslo', Ophiopogon japonicus (Thunb.) Ker-Gawl., and Hemerocallis × `Aztec Gold' was significant and therefore unacceptable. Chemical name used: 3-isopropyl-1H-2,1,3-benzothiadiazin-(4)-3H-one 2,2-dioxide (bentazon).

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J. G. Norcini and J. H. Aldrich

The possible loss of IBA for use in propagation of woody ornamental has prompted increased interest in the registration of phenyl indole-3-thiobutyrate (P-ITB), a potential alternative. Two products currently available, CYTOKIN and ROOTS, warrant investigation since ROOTS stimulates rooting of a few species (R. Poincelot, pers. comm.) and CYTOKIN is a similar product. Both contain naturally-derived cytokinin and algal extracts. The purpose of this study was to determine the rooting activity of these products utilizing the mung bean bioassay. Seeds of Vign a radiata `Texsprout' were sterilized in 0.5% sodium hypochlorite for 10 min, rinsed, aerated for 24 hr in tap water, and then sown in coarse vermiculite (1 cm deep) held in plastic trays. Growth of the seedlings and the bioassay were conducted in a growth chamber under a 16-hr photoperiod, an irradiance of 85 μE, 27.5°C during the day and 21.1 C at night. ROOTS enhanced rooting better than 0.1 mM NAA and was 68% that of 0.1 mM IBA. CYTOKIN at .2, 1, 2, 4, 5, or 10% did not stimulate rooting; additional concentrations are currently being tested.

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James J. Marois and Jeffrey G. Norcini

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.

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J.G. Norcini, J.M. McDowell and J.H. Aldrich

The use of dikegulac in production of hanging baskets (4.5-liter capacity) of Bougainvillea `Rainbow Gold' was investigated under decreasing daylengths and high temperatures. Liners treated with a single application of 1200 ppm dikegulac 4 weeks after transplanting and pruning (WATP) resulted in the only marketable hanging baskets 9 WATP. Application of 1200 ppm dikegulac 4 WATP enhanced flowering and aesthetic quality compared with plants that had only been pruned. Bract size did not appear to be reduced. Plant width tended to increase as time of application was delayed. Dikegulac had no effect on height or branching. Chemical name used: sodium salt of 2,3:4,6-bis-O-(l-methylethylidene)-a-L-xylo-2-hexulofuranosonic acid (dikegulac-sodium).

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J.G. Norcini, J.M. McDowell and J.H. Aldrich

The use of dikegulac foliar sprays in production of 4.5-liter hanging baskets (25.4-cm in diameter) of `Barbara Karst' bougainvillea [Bougainvillea ×buttiana (Bougainvillea glabra Choicy X Bougainvillea peruviana Humb. & Bonpl.) `Barbara Karst'] and `Rainbow Gold' bougainvillea (Bougainvillea `Rainbow Gold') was investigated under high temperatures (27.5-32C) and two production seasons (late spring to early summer and midsummer to early fall). During the late production season, liners pruned at transplanting (0 weeks) and treated with 1600 mg dikegulac/liter at 0 and 4 weeks resulted in plants with more flowers than that of controls (pruned only at 0 and 4 weeks), with `Barbara Karst' having a slightly compact, pendulous growth habit similar to that of controls. Dikegulac enhanced flowering compared with controls during midspring to early summer, but it did not result in plants with a slightly compact pendulous growth habit. These results suggest that a foliar spray of 1600 mg dikegulac/liter could substitute for the second pruning during hanging basket production of `Barbara Karst'. Chemical name used: sodium salt of 2,3:4,6-bis-O-(1-methylethylidene)-α-xylo-2-hexulofuranosonic acid (dikegulac-sodium).

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J.G. Norcini, J.H. Aldrich and J.M. McDowell

Foliar spray application of dikegulac at 1600 mg·liter-1 during production of Bougainvillea glabra Choicy `Mauna Kea White', and Bougainvillea `Raspberry Ice', `Royal Purple', `Summer Snow', and `Temple Fire' in 4.5-liter hanging baskets (25.4 cm in diameter) was investigated in relation to flowering. The effect of foliar-applied dikegulac at 0, 400, 800, 1200, and 1600 mg·liter-1 on bracteole size of `Mauna Kea White' was also determined. Liners of `Temple Fire' pruned at transplanting (0 weeks) and sprayed with dikegulac at, 0 and 4 weeks had increased flowering and a slightly more compact, pendulous growth habit than plants that had only been pruned at 0 and 4 weeks. Dikegulac had little to no effect on flowering of the other cultivars. Under late-spring to early summer conditions (generally increasing temperatures), bracteole size of `Mauna Kea White' was reduced ≈25 % by 400 mg dikegulac/liter compared to nontreated plants; 800 to 1600 mg dikegulac/liter reduced bracteole size ≈37%. Under late-summer to mid-fall conditions when the weather was cooler and wetter, dikegulac had little to no effect on bracteole size; however, bracteoles of nontreated plants were ≈25% smaller than those of plants grown under the warmer and drier conditions of late spring to early summer. Chemical name used: sodium salt of 2,3:4,6-bis -O- (1-methylethylidene) -α-l-xylo- 2-hexulofuranosonic acid (dikegulac).

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P.C. Andersen, J.G. Norcini and G.W. Knox

Leaf physiology and plant growth of Rhododendron × `Pink Ruffles' were compared under conditions of 100% sun and under polyethylene shadecloth with specifications of 69%, 47%, and 29% light transmittance. Net CO2 assimilation (A) and stomatal conductance to water vapor (gs) were often reduced for plants in the 100% sun regime, although few differences existed among the 69%, 47%, and 29% sun treatments. Stomatal conductance was very sensitive to leaf to air vapor pressure deficits (VPD), as evidenced by an 85% increase in gs with a decrease in VPD from 3.2 to 2.2 kPa. Light response curves established for plants after 54 days of exposure to 100% and 29% sun were similar, although A was consistently higher at all levels of photosynthetic photon flux for plants in the 29% sun regime. Maximum A was ≈5 and 6 μmol·m-2·s-1 for 100% and 29% sun-grown plants, respectively; light saturation occurred at ≈ 800 μmol·m-2·s-1 Midday relative leaf water content and leaf water potential were not affected by sun regime. The plant growth index decreased with increasing light level. Leaf, stem, and root dry weights; total leaf number and dry weight; total and individual leaf area; dry weight per leaf; and leaf chlorophyll concentration were reduced in 100% sun, yet few differences existed among the 69%, 47%, and 29% sun treatments. Shoot: root ratio and specific leaf weight were proportional to light level. Plants grown in the 100% sun regime were chlorotic and dwarfed, and plants in 29% sun were not sufficiently compact. One year after transplanting to the field under 100% sun, plants of all treatments were chlorotic and failed to grow.

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J.G. Norcini, P.C. Andersen and G.W. Knox

Leaf physiology and plant growth of Photinia x fraseri Dress were assessed when grown under full sunlight or (100% sun) or polypropylene shadecloth with a light transmittance of 69%, 47%, or 29% sun. Plants in 69% or 47% sun usually had the highest midday net CO2 assimilation rates (A). Net CO, assimilation rate was most dependent on photosynthetic photon flex (PPF R2 = 0.60), whereas stomata] conductance to water vapor was primarily influenced by vapor pressure deficit (R2 = 0.69). Stomatal conductance was often inversely related to sun level, and intercellular CO2 concentration was often elevated under 29% sun. Midday relative leaf water content and leaf water potential were unaffected by light regime. Light-saturated A was achieved at ≈ 1550 and 1150 μmol·m-2·s-1 for 100% and 29% sun-grown plants, respectively. Under 29% sun, plants had a lower light compensation point and a higher A at PPF < 1100 μmol·m-2·s-1. Total growth was best under 100% sun in terms of growth index (GI) increase, total leaf area, number of leaves, and dry weight (total, stem, leaf, and root), although plants from all treatments had the same GI increase by the end of the experiment. Plants in all treatments had acceptable growth habit (upright and well branched); however, plants grown in 29% sun were too sparsley foliated to be considered marketable. There were no differences in growth among the four treatments 7 months after the Photinia were transplanted to the field.

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J. G. Norcini, U. K. Yadav and J. M. McDowell

Bougainvillea spectabilis `Scarlett O`Hara' is an extremely fast-growing plant that can require frequent pruning during production. The purpose of this study was to evaluate the effectiveness of uniconazole and daminozide in controlling growth.

Plants growing in 3.8-liter containers were pruned 3 days before uniconazole (SUMAGIC .05%L) or daminozide (B-NINE SP) was applied. The treatments were 1) uniconazole folier spray at 0, 50, 100, 150, or 200 ppm, 2) uniconazole drench at 0.5, 1.0, 2.5, or 5.0 mg ai/plant, and 3) daminozide foliar spray at 0, 2500, 5000, 7500, or 10,000 ppm. Uniconazole and daminozide primarily inhibited increase in the width of bougainvillea; height was only repressed at the high rates of uniconazole or daminozide (only 10,000 ppm). The 200 ppm uniconazole spray and the low drench rates reduced the growth rate for 3 to 5 weeks. Drenches of 2.5 or 5.0 mg ai/plant resulted in excessive growth reduction.