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Harry K. Tayama and Stephen A. Carver

Uniconazole spray or drench applications to `Yours Truly' zonal geranium (Pelargonium × hortorum L.H. Bailey) and `Bright Golden Anne' and Yellow Favor' chrysanthemums [Dendranthema ×grandiflorum (Ramat.) Kitamura] were made to evaluate efficacy and identify optimum application concentrations. Spray applications at 10 mg a.i./liter retarded stem elongation in unpinched zonal geranium comparable to chlormequat at 1500 mg a.i./liter. `Bright Golden Anne' was more sensitive to uniconazole than `Yellow Favor'. Uniconazole spray concentrations of 20 to 30 mg a.i./liter retarded plant height equal to daminozide at 5000 mg a.i./liter. Chemical names used: 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat); butanedioic acid mono (2,2-dimethylhydrazide) (daminozide); (E)-(S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ene-3-ol (uniconazole).

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A. Hagiladi and A.A. Watad

Potted Cordyline terminalis L. `Prins Albert', a foliage plant, was treated with foliar sprays or growth medium drenches of paclobutrazol for plant growth control. Paclobutrazol effectively reduced shoot length measured 4 months following application, the drench being more effective than the spray. Application of paclobutrazol at 200 ppm by either method gave a desirable compact and marketable product. Drench applications at 1000 ppm promoted side-shoot formation. Leaf morphology was altered from an elongated to a more oval form as the paclobutrazol concentration increased, but leaf count was not affected by paclobutrazol, except for the highest drench concentration, which reduced leaf count by 10%. Chemical name used: β– [(4-chlorophenyl)methyl] –α– (1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

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David A. Gilbertz

Spray applications of 15 or 30 mg uniconazole or 30 or 60 mg paclobutrazol/liter (20 ml/1.5-liter pot) were sprayed 0, 2, or 4 weeks after pinching of Dendranthema × grandiflorum (Ramat.) Kitamura `Bright Golden Anne' plants. Plants were shorter the earlier growth regulators were applied. Plants were more responsive to uniconazole, requiring paclobutrazol at up to four times the uniconazole concentration to achieve the same height control. Time to flowering was also lengthened the earlier applications were made, up to 3 days compared to nontreated plants. Flower diameter was only minimally affected by the treatments. Chemical names used (2RS,3RS)-1-(4-chlorophenyl)-2-1,1-dimethylethyl)-(1H-1,2,4-triazol-1-yl)pentan-3-ol(-paclobutrazol);(E)-l(p-chlorophenyl) -4,4-dimethyl-2-(1,2,4-triazol-1-yl-1-penten-3-ol) (uniconazole).

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Steven E. Newman, Michael J. Roll, and Ronald J. Harkrader

Quaternary benzophenanthridine alkaloids (QBAs) isolated from plants in the family Papaveraceae are effective for the control of some fungal diseases. Extracts from Macleaya cordata, a species rich in QBAs, were formulated at 150 mg·L–1 QBA for spray application to greenhouse roses (Rosa sp.) infected with Sphaerotheca pannosa var. rosae (powdery mildew). The QBA formulation was applied at 10-day intervals. For comparison, copper sulfate pentahydrate, piperalin, and fenarimol also were applied to mildewinfected plants within the same greenhouse at their respective labeled rates. One day after treatment, visible symptoms of mildew infection were reduced 60% by QBA, whereas fenarimol, copper sulfate pentahydrate, and piperalin reduced the symptoms of infection 50%, 75%, and 85%, respectively. Subsequent studies demonstrated that a tank mix of QBA and piperalin provided enhanced control of powdery mildew on rose. Results from this study indicate that QBAs have the potential to be developed as a biorational fungicide for greenhouse use with both fungicidal and fungistatic activity.

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James E. Altland, Charles H. Gilliam, and Glenn Wehtje

Herbicide use is an important component of weed management in field nursery crops. No single herbicide controls all weed species. Oxyfluorfen, simazine, and isoxaben are preemergence herbicides effective against broadleaf weeds. Oryzalin, pendimethalin, and prodiamine are effective in preemergence control of grasses and some small-seeded broadleaf weeds. Metolachlor is the only herbicide currently labeled for nursery crops that is effective in preemergence nutsedge (Cyperus) control. Fluazifop-butyl, sethoxydim, and clethodim are selective postemergence herbicides used for grass control. Glyphosate, paraquat, and glufosinate are nonselective postemergence herbicides used in directed spray applications for broad-spectrum weed control. Bentazon, halosulfuron, and imazaquin are effective postemergence nutsedge herbicides. These herbicides are discussed with respect to their chemical class, mode of action, labeled rates, and current research addressing their effectiveness in nursery crops.

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I. Papageorgiou, P. Giaglaras, and E. Maloupa

Growth retardants allowed production of more uniform, compact, flowering plants for commercial use of lavender (Lavandula stoechas). Paclobutrazol at 200, 400 and 600 mg·L-1 (ppm) was sprayed in a single or double application. Chlormequat was applied at 4000, 6000 and 8000 mg·L-1 in single, double or triple spray applications repeated every 13 days. Paclobutrazol reduced lateral shoot elongation and plant height, increased the number of nodes within lateral shoots, but delayed time to anthesis. In contrast, chlormequat reduced plant height with no effect on flowering. Paclobutrazol potentially may be used commercially on lavender at rates of 200 to 400 mg·L-1 in single or double applications. The same result may be achieved with chlormequat by using 4000 to 6000 mg·L-1 in three or more applications.

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Ed Stover, Dominick Scotto, Chris Wilson, and Masoud Salyani

Foliar application of spray materials is an integral component of commercial citrus production. An intensive assessment of spray application practices has been stimulated by low fruit value and increased concern about potential surface water contamination in the Indian River citrus region of Florida. Many publications report research results regarding distribution of spray materials within orchards and off-target deposition, but interpretation is challenging because so many factors influence spray results, and integrating this information into practical recommendations is difficult. Canopy geometry and density are prominent factors contributing to variable deposition and spray drift. Environmental factors such as temperature, relative humidity, wind speed, and wind direction also greatly influence spray deposition and drift, and substantial changes can occur within seconds. In addition the physical and/or mechanical set up of the sprayer interact significantly with the other factors. A better understanding of these interactions should help growers optimize spray effectiveness and efficiency while reducing potential off-target effects.

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Jeff A. Anderson

One method of plant freeze protection involves the application of compounds that promote freeze avoidance or tolerance. FreezePruf, a commercially available product recently marketed to improve both freeze avoidance and tolerance, contains polyethylene glycol, potassium silicate, glycerol, silicone polyether surfactant, and a bicyclic oxazolidine antidessicant. The goal of the present study was to evaluate the protection level provided by FreezePruf using laboratory-based methods involving plants and plant parts from species capable and incapable of low-temperature acclimation. FreezePruf did not lower the freezing temperature of pepper (Capsicum annuum) seedlings, celosia (Celosia argentea) seedlings, detached tomato (Solanum lycopersicum) leaves, or postharvest tomato fruit. Spray application of the putative cryoprotectant did not increase the freeze tolerance of bermudagrass (Cynodon dactylon) crowns or stolons. It is possible that a greater level of protection could be achieved with other species or different experimental protocols.

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Levava Roiz, Uzi Ozeri, Raphael Goren, and Oded Shoseyov

Aspergillus niger B-1 (CMI CC 324626) extracellular RNase (RNase B1) was purified to homogeneity. It was found to contain two isoforms of 32- and 40-kDa glycoproteins, sharing a 29-kDa protein moiety. Optimal RNase activity was observed at 60 °C and pH 3.5. In `Almog' peach [Prunus persica (L.) Batsch (Peach Group) `Almog'] and `Murcott' tangerine (Citrus reticulata Blanco `Murcott') the enzyme inhibited pollen germination and pollen tube growth in vitro as well as in vivo. In field experiments, spray application of the RNase caused a reduction in `Fantasia' nectarine [Prunus persica (L.) Batsch (Nectarine Group) `Fantasia'] fruit set and interfered with embryo development. The biological effect of the RNase may be of horticultural value, due to its potential to control fertilization.

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D. Michael Glenn, Ernesto Prado, Amnon Erez, James McFerson, and Gary J. Puterka

Particle film technology is a new tool for tree fruit production systems. Trials were performed in Santiago, Chile, and Washington and West Virginia to evaluate the effect of particle film treatments on apple [Malus sylvestris (L.) Mill var domestica (Borkh.) Mansf.] fruit temperature and the incidence of solar injury. Fruit surface temperature was reduced by the application of reflective particles and the amount of temperature reduction was proportional to the amount of particle residue on the fruit surface. Effective solar injury suppression was achieved with spray applications of 45 to 56 kg·ha-1 of a reflective, processed-kaolin particle film material in concentrations ranging from 3% to 12% in some of the locations. The timing of application to suppress solar injury was not clearly defined. The processed-kaolin particle film material was highly reflective to the ultraviolet wavelengths and this characteristic may be important in reducing solar injury to both fruit and leaves.