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Dorcas K. Isutsa, Marvin P. Pritts, and Kenneth W. Mudge

A protocol is presented that enables a propagator to produce field-sized blueberry transplants within 6 months of obtaining microshoots from tissue culture. The protocol involves subjecting microshoots to ex vitro rooting in a fog chamber under 100 μmol·m–2·s–1 photosynthetic photon flux for 7 weeks, transferring plants to a fog tunnel for 2 weeks, then to a greenhouse for 7 more weeks. Plant survival and rooting of cultivars Berkeley (Vaccinium corymbosum L.) and Northsky (Vaccinium angustifolium ×corymbosum) were near 100% under these conditions. Plantlets in fog chambers receiving 100 μmol·m–2·s–1 grew rapidly, while those at lower irradiance levels grew more slowly, and supplemental CO2 enhanced growth only at 50 μmol·m–2·s–1. Growth rates slowed when plants were moved into the fog tunnel; but by the end of 16 weeks, plants that were under high irradiance in the fog chamber had root systems that were 15 to 30 times larger than plants under low irradiance. Within 6 months, these plants were 30 to 60 cm tall and suitable for field planting.

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Houchang Khatamian and G.A. van der Hoeven

Softwood cuttings of Cotoneaster multiflorus Bunge were collected on 11 June 1996 from a large specimen shrub located at Manhattan, Kan. Uniform cuttings 12 to 15 cm long were dipped in 0, 5000, 10,000, 15,000, or 20,000 ppm IBA solution for 10 sec and Hormodin™ #2. Cuttings were stuck in a rooting mix consisting of 30% Canadian sphagnum peat and 70% perlite (v/v). The experiment was conducted in a greenhouse either equipped with a fog generator (Humidifan, turbo XE 1000) or the conventional intermittent mist system. The fog generator and the mist system were operated for 12 hr/day. On 12 Aug.1996, the experiment was terminated and cuttings were evaluated for percent rooting. Cuttings treated with 5000 ppm IBA rooted 100% either under mist or with the fog system. Twelve percent of the cuttings under mist rooted when treated with no IBA or Hormodin™ #2, as compared to 50% and 40% under fog, respectively. The rooting quality under the fog system was better than the mist. Rooted cuttings were potted in 15-cm plastic containers filled with Metro Mix™ 702 and were grown under standard greenhouse environment for several weeks prior to planting outdoors.

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Rhonda J. Smith

The effect of sunlight exposure on yield, fruit composition, amount of damaged clusters, and berry temperature was evaluated in a terraced, hillside `Cabernet Sauvignon' vineyard on the north coast of California. Each terrace contained two vine rows identified as “inside” and “outside” relative to the terrace surface. The standard canopy management practice of removing lateral shoots from below the clusters was imposed with three modifications (“umbrella”, “fogger”, and “umbrella+fogger”) and an unmodified control. Applications of a kaolin-based particle film were made to unmodified canopies and a final treatment consisted of leaving lateral shoots. Canopies with umbrella modifications were not fully vertically shoot positioned. Fogger emitters directed water into the cluster area when ambient temperature reached 33.9 °C beginning in mid-July for a total of 16 fogger-events through 8 Sept. 2004. Treatments were harvested 17 Sept. Yield was affected by row type but not treatment, and inside and outside rows produced an average of 2.1 and 3.4 kg/vine, respectively. Particle film applications significantly reduced berry surface temperatures in the afternoon of two measurement dates by 0.7 and 1.5 °C, respectively. Applications did not significantly affect fruit maturity indices when compared to fruit in the control; however, at the 7% probability level, berry samples from vines that had been treated with kaolin-clay had lower °Brix than samples from control vines. The mean range of sunburn fruit across all treatments was 0.2 to 1.4 clusters per vine. Umbrella and umbrella+fogger treatments significantly reduced the number of damaged clusters (P < 0.05).

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Jayesh B. Samtani, Celeste Gilbert, J. Ben Weber, Krishna V. Subbarao, Rachael E. Goodhue, and Steven A. Fennimore

effect of solarization on soil pests is inconsistent as a result of the presence of a marine fog layer and low summer soil temperatures. Steam has long been used in nursery and greenhouse crop production systems to control soilborne pests, and studies

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Thomas W. Walters, LeRoy A. Ellerbrock, Jan J. van der Heide, James W. Lorbeer, and David P. LoParco

Greenhouse and field methods were developed to screen Allium spp. for resistance to botrytis leaf blight (causal agent Botrytis squamosa Walker). In greenhouse evaluations, plants were sprayed with laboratory-grown mycelial fragment inoculum and were incubated at 20C in a chamber with an atomizing fogger. For field inoculations, a portable fog system with windbreaks was erected around experimental plots, and the plants were sprayed with the inoculum on evenings when windless, temperate (18 to 22C) conditions were forecasted. The most effective mycelial fragment inoculum was <21 days old and had ≈45 to 50 colony-forming units/μl, resulting in an absorbance at 450 nm of 0.2 to 0.3. Rubbing the wax cuticle from leaves was essential to disease development in greenhouse but not in field experiments. Evaluations of eight Allium species, including 55 A. cepa L. accessions, were in agreement with previous studies.

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Faheem Aftab, Katayoun Mansouri, and John E. Preece

The objectives of this research were to study the effects of three environments (lab, mist, or fog), four media treatments [perlite, vermiculte, 1 perlite: 1 vermiculite (by volume), or a control (empty flats)] and zerotol treatments on shoot forcing and subsequent transfer of explants to in vitro conditions. Stem segments from field-grown trees were cut to 40-cm lengths before being placed in flats with the media treatments. Half of the flats under mist and fog were drenched weekly with zerotol (0.18% H2O2). In a separate study, silver maple was forced under mist and drenched weekly with zerotol at 0%, 0.09%, 0.108%, 0.135%, 0.18%, 0.27%, or 0.54% H2O2. Shoots (≥5 cm) were harvested and nodal and shoot tip explants were surface disinfested and placed in vitro on DKW medium with 10-8 M thidiazuron plus 1.0 μM indolebutyric acid. Species did not interact with environment, media, or zerotol treatment, and silver maple produced a mean of 6 shoots per stem segment, while green ash produced a mean of 1.2 shoots. There was a significant interaction among perlite, vermiculite and environment, with the most shoots (6.7/stem segment) produced under mist in the perlite: vermiculite mix. Silver maple explants from the lab had only 4% microbial contamination, whereas 68% of explants from fog and 92.2% of explants from mist were contaminated. When forcing was under fog, in perlite, and drenched with zerotol, explants had a 43% rate of contamination. In a separate study, when silver maple stems were placed under mist and drenched weekly with 0.18% H2O2, 46% (18 of 39 explants) established cleanly in vitro. Contamination was higher with misted explants that were drenched with higher or lower concentrations of zerotol.

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Katharine B. Perry

Basic meteorology as it applies to frost-freeze events and a discussion of the methods of frost protection are included in this article. The presentation of basic meteorology includes descriptions of heat transfer, energy exchange, inversion, frost, freeze, microclimate, air versus crop temperature, and forecasts and warnings in the context of how each of these in involved in frost-freeze events. The second part of the paper describes the major methods of frost protection for commercial crops. The methods included are site selection, irrigation (overhead, undercanopy, man-made fog, flooding), wind machines, heaters, covers, and sprayable materials.

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John E. Preece, Carl A. Huetteman, W. C. Ashby, and Paul L. Roth

During the research phase, a system was developed to clonally micropropagate silver maple. Explant performance was best on DKW medium with 10 nM thidiazuron, and explants commonly developed 1 7 shoots after three months and over 60 shoots that could be rooted after four months in vitro. Plants were rooted (>90%) and acclimatized under intermittent mist and transplanted to an outdoor nursery bed. However, results were different during the production phase when 90 clones were propagated. Shoot proliferation rates were lower, differences in clonal response and worker efficiency were apparent, mass rooting under mist was inconsistent and acclimatization problems arose. The mean rooting was 46% under mist because of uneven coverage. Only 56% of rooted plantlets acclimatized which resulted in an overall efficiency of 26%. Partial solutions included root initiation in vitro, and use of fog for acclimatization.

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Norman Pellett and David Heleba

Gibberellic acid (GA) and benzyladenine (BA) were evaluated for stimulating shoot growth during rooting of softwood cuttings of two species whose propagation causes bud dormancy. Cuttings of Betula papyrifera Marsh. and Forsythia mandschurica Uyeki `Vermont Sun' were treated with 4 levels of GA or 2 levels of BA while rooting in a polyethylene-covered chamber humidified by fog. GA treated Forsythia produced longer shoots, but did not increase the percentage of cuttings producing new shoots (overcoming dormancy). GA treatments of Betula at 1000, 2500, and 5000 ppm resulted in reduced shoot growth and caused death of most cuttings. BA at 1000 ppm in a solution of ethanol, DMSO, and water was detrimental to cuttings.

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Arnold H. Hara, Trent Y. Hata, Victoria L. Tenbrink, Benjamin K.S. Hu, and Mike A. Nagao

Postharvest treatments significantly reduced or eradicated pests on various tropical cut flowers and foliage. Immersion in water at 49° C for 10 minutes killed armored scales on bird of paradise leaves, Strelitzia reginae Banks, as well as aphids and mealybugs on red ginger, Alpinia purpurata (Vieill.) K. Schum. Vapor heat treatment for 2 hours at 45.2° C provided quarantine security against armored scales on bird of paradise leaves. A 5 minute dip in fluvalinate combined with insecticidal soap eliminated aphids and significantly reduced mealybugs on red ginger. A 3 minute dip in fluvalinate, a 3 minute dip in chlorpyrifos, or a 3 hour fog with avermectin-B significantly reduced thrips on orchids, Dendrobium spp., without injury to the flowers. No postharvest treatment was both effective and nonphytotoxic on all commodities.