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W.A. Bergfield, D.N. Sasseville, R.J. Kremer, and T. Souissi

Pesticides are used extensively in ornamental production. Studies of repeated pesticide applications indicate that microbial changes occur in the rhizosphere of the plant. In addition to controlling the target pest, often a population shift of bacteria may occur. This has been previously shown in research associated with leatherleaf fern [Rumohra adiantiformis (Forst.) Ching] and the fungicide benomyl. Rhizobacteria (root-associated bacteria) of anthurium (Anthurium andraeanum) were investigated with respect to total populations and isolates that are potentially phytotoxic. The anthurium sample roots were taken from commercial Jamaican production sites. The sites had either a benomyl or non-benomyl history. Rhizobacterial populations were estimated by dilution plating and subcultures were taken for a phytotoxicity bioassay. Micrographs of samples were prepared to examine treatment effects on the morphology of roots. Rhizobacteria populations were frequently at 106 colony forming units per gram fresh weight. Consistently, greater than 50% of the isolates from each treatment were potentially phytotoxic. However, in the benomyl history samples, there was a greater diversity of phytotoxic isolates.

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Larry D. Howery, Dale L. Nolte, Lawrence M. Sullivan, and Michael W. Kilby

The objective of our experiment was to determine if the application of two deer repellents to six grape cultivars (Vitis vinifera L.) caused significant phytotoxic effects, production losses, or altered the sensory characteristics of wine. We evaluated fifteen single vine plants from six different cultivars in a randomized block design that included the two repellent treatments and an untreated control. During spring 1997, we applied repellents biweekly from budbreak until flowering (2 Apr. to 14 May). Plantskyyd was applied more frequently than recommended by the product label (for trees) due to rapid emergence of unprotected shoot growth in vineyards. Hot Sauce and Plantskydd caused some initial minor phytotoxicity during 1997, however, the yield and phytotoxicity of treated plants were similar to controls by harvest. A panel detected a significant difference in the color, aroma, or taste of `Chardonnay' wine made from grapes treated with repellents compared to wine made from untreated control grapes (P = 0.001 for Hot Sauce; P = 0.05 for Plantskydd). We conclude that Hot Sauce and Plantskydd did not cause serious production losses or phytotoxic effects for the six cultivars treated. However, both Hot Sauce and Plantskydd significantly altered the sensory attributes of Chardonnay wine, which may preclude the use of chemical repellents in wine grape vineyards under the experimental conditions applied in our study.

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Chuck Ingels and John Roncoroni

growth was substantial, requiring three to four periods of extensive hand weeding until full establishment of the turf. In a New Zealand study, eight postemergent herbicides were evaluated for weed control and plant phytotoxicity after spraying over

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James D. Hansen, Harvey T. Chan Jr., Arnold H. Hara, and Victoria L. Tenbrink

Phytotoxicity from hydrogen cyanide (HCN) fumigation was measured in several varieties of Hawaiian cut flowers and foliage (Zingiberaceae, Heliconia, Orchidaceae, Marantaceae, Lycopodiaceae, Agavaceae, Proteaceae) as a potential disinfestation treatment. Concentrations tested were 2500, 3700, 4600, and 5500 ppm HCN for 30 min. All foliage and most heliconia were undamaged at fumigation levels of 5500 ppm HCN; most protea and `Midori' anthuriums were uninjured at 4600 pm HCN; red and pink ginger were uninjured at 3700 ppm HCN; and all pincushion protea showed phytotoxicity to HCN. Red ginger was quickly damaged when exposed to sunlight immediately after treatment at 2500 ppm HCN. No injury was observed in simulated shipment tests of red ginger and `Ozaki' anthuriums fumigated at 2500 ppm HCN. Wet, red ginger flowers longer than 6 cm were damaged at 2500 ppm HCN, whereas shorter flowers were uninjured. Wet `Ozaki' anthuriums showed phytotoxicity only at 4600 ppm HCN. Wet, treated lycopodium and bamboo orchid foliage was not injured. The number of marketable days and shelf life of the treated plant material were estimated from the visual ratings.

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David Staats, David Hillock, and James E. Klett

Five preemergence herbicides were applied to seven herbaceous perennials to evaluate weed control efficacy and phytotoxicity. Different species were used each year. The species used during 1992 were coneflower (Rudbeckia fulgida Ait. `Goldstrum'), common foxglove (Digitalis purpurea L. `Excelsior'), Shasta daisy (Leucanthemum ×superbum Bergmans `Alaska'), Stokes's aster (Stokesia laevis Greene `Blue Danube'), and avens (Geum Quellyon Sweet `Mrs. Bradshaw'). The species used in 1993 were woolly yarrow (Achillea tomentosa L.) and woolly thyme (Thymus pseudolanuginosus Ronn.). The herbicides and rates were napropamide (Devrinol 10G) at 4 and 8 lb a.i./acre; metolachlor (Pennant 5G) at 4 and 8 lb a.i./acre; oxyfluorfen+oryzalin (Rout 3G) at 3 and 12 lb a.i./acre; trifluralin (Treflan 5G) at 4 and 8 lb a.i./acre; and oxadiazon (Ronstar 2G) at 4 and 8 lb a.i./acre. Plants were grown in no. 1 containers and weed seeds were sown onto the substrate surface. Two control treatments, no herbicides but with weeds (weedy control), and no weeds or herbicides (weed-free control) also were evaluated. Weed control was effective and similar for all herbicides tested. Napropamide at 8 lb a.i./acre caused stunting in foxglove (20% to 45% less growth compared to weed-free control). Oxyfluorfen + oryzlain at 12 lb a.i./acre caused severe phytotoxicity (≈80% to 95% of plant injured) and stunted the growth (70% to 80% less growth, sometimes plant death) of woolly yarrow. Woolly thyme was stunted by all herbicides when applied at the recommended rates (42% to 97% less growth compared to control) except for oxadiazon and oxyfluorfen + oryzlain. Woolly thyme appeared to be more susceptible to phytotoxicity due to its less-vigorous growth habit and shallow, adventitious roots that were in contact with the herbicide.

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James H. Aldrich and Jeffrey G. Norcini

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.

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Arnoldo Michel-Rosales, Javier Farias-Larios, Juan Alberto Osuna-Castro, Elpidio Peña-Beltrán, Juan Manuel González-González, and Héctor Javier Garibay-Bautista

At present, pitahaya (Hylocereus undatus Britt and Rose), a nonconventional crop and cactus native from Mexico, is considered very promising because of its high adaptability and tolerance to extreme agricultural conditions of tropical regions (poor soils, drought, and elevated temperatures), where they are cultivated. In addition, pitahaya fruit is well-accepted and identified as a nutraceutical food that lowers cholesterol and glucose levels in blood and might prevent stomach and colon cancers. However, little or no scientific information on chemical control alternatives of weeds in pitahaya commercial plantings have been generated. In this work, the phytotoxicity degree of seven commercial herbicides (metribuzin, glyphosate, glyphosate trimesium, paraqut, paraquat+diuron, atrazine, and halosulfuron methyl) in pitahaya plants grown under plant nursery conditions was assessed. A completely randomized design with 12 replications was used. The experimental unit was a flowerpot with a 5-month-old plants. The phytotoxicity degree was evaluated at 3, 7, 14, and 21 days after application using the scale proposed by EWRS. The herbicides that caused injury to the plants were paraqua+diuron (79%) and paraquat (77%), respectively. Metribuzin, halosulfuron-methyl, and atrazine did not cause any injury to the plants.

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Johan Desaeger and Alex Csinos

The effects of drip-applied 1,3-dichloropropene (1,3-D) and chloropicrin on fumigant soil gas levels and growth of vegetable seedlings were investigated in three separate tests in Tifton, Ga. Tests were conducted in Spring 2002, Fall 2002, and Spring 2003. Phytotoxicity of 1,3-D + chloropicrin was induced in the 2002 tests by applying progressively higher rates (0 to 374 L·ha–1) of drip-irrigated InLine (an emulsifiable formulation (EC) containing 60.8% 1,3-D and 33.3% chloropicrin) and planting vegetable seedlings within four days after application. Vegetables evaluated were tomato, pepper and cucumber (Spring 2002), and tomato and squash (Fall 2002). In Spring 2003, the effects of 1,3-D formulation (InLine versus Telone EC, an EC containing 94% 1,3-D), plastic mulch type [low density polyethylene (LDPE) versus virtually impermeable film (VIF)] and drip tape configuration (one versus two drip tapes) on fumigant soil gas levels and growth of tomato were investigated. Tomato was planted after the recommended 3-week waiting period. Fumigant concentrations in soil were measured using Gastec detection tubes at 1 to 4 days after drip fumigation in all three tests. Measured fumigant soil gas concentrations were correlated with fumigant application rates in Spring 2002, but not in Fall 2002. Vegetables were visibly affected by residual fumigant levels in the soil and showed symptoms such as leaf chlorosis (cucumber, squash and pepper), leaf bronzing (tomato) and stem browning and stunting (all crops). Fumigant soil air levels were negatively and linearly correlated with different plant growth parameters, in particular plant vigor. The cucurbit crops showed an immediate response and high mortality within 1 week after planting. Surviving plants recovered well in fall. The solanaceous crops showed a more delayed response and lower mortality rates. However, phytotoxic effects with tomato and pepper were more persistent and plants did not seem to recover with time. Overall, fumigant residue levels and potential phytotoxicity were greater in spring than in fall. Greater fumigant soil concentrations were measured under VIF as compared to LDPE plastic mulch. The effect of drip-tape configuration varied with the type of plastic mulch that was used. The double-tape treatment resulted in lower fumigant levels at the bed center under LDPE mulch, and higher fumigant levels at the bed shoulder under VIF mulch. The formulation containing 94% 1,3-D resulted in higher soil fumigant levels as compared to the formulation containing 61% 1,3-D and 33% chloropicrin, especially with VIF mulch. Early plant vigor of tomato was negatively correlated with fumigant soil gas levels, and was especially poor following drip fumigation with 94% 1,3-D under VIF mulch.

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Liping Zhen and Leslie H. Fuchigami

Hydrogen cyanamide (CY) induced earlier, more uniform, and a higher percentage of budbreak in poplar (Populus alba × P. gradidentata, N C 5339). c y was phytotoxic at 0.5 M or higher concentration. Percent budbreak increased and percent dieback decreased when plants were treated with a mixture of CY and Cys. No difference was found in percent budbreak or dieback between plants treated with CY alone and a mixture of CY and Ser. Mixing CY with Cys concentrations in vitro reduced the percentage of the cyano group, and mixing of Cys with CY concentrations decreased the percentage of the SH group remaining in the mixture. Mixing CY with Ser concentrations in vitro had no effect on CY level. These studies suggest that the SH group reacts with CY directly and the improvement of budbreak and toxicity caused by mixing CY and Cys may be due to the reduction of CY concentration.

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Timothy K. Broschat

Twenty-two preemergent herbicides were applied at their maximum labeled rates and twice those rates to determine their safety and effectiveness on areca palm [Dypsis lutescens (H. Wendl.) Beentje & Dransf.], pygmy date palm (Phoenix roebelenii O'Brien), and mexican fan palm (Washingtonia robusta H. Wendl.). Two products, dichlobenil and metolachlor showed consistent phytotoxicity on all three species. Several of the remaining products caused death of the apical meristem in mexican fan palms and reduced growth rates in pygmy date palms, but most caused little damage to areca palms. Herbicides applied as sprays generally remained effective for 2 to 4 months, whereas granular products, especially those containing oxyfluorfen plus another chemical, were effective for up to 8 months.