A survey was conducted in 2000-01 to provide a comprehensive description of Virginia's commercial greenhouse industry. A total of 274 responses were analyzed. Responses were categorized based on the amount of heated greenhouse space: small, medium, large, or other (including part-time). The survey included questions about growing space, number of employees, education and experience of respondent, crops grown, gross receipts, and target markets. Seventy-five percent of the respondents were owners or owners/growers and respondents reported an average of 15 years experience. Most greenhouse operations were classified as small or less than 10,000 ft2 (929.0 m2). A wide variety of crops were reported, with more than 50% growing bedding plants and nearly 50% growing herbaceous perennials in the greenhouse. Market outlets were about equally divided between wholesale and retail.
Epicuticular lipids were extracted from the foliage of six deciduous and one evergreen azalea genotypes (Rhododendron sp.) and identified by gas chromatography-mass spectrometry. The relationship of leaf-surface lipid composition with measures of resistance to azalea lace bug, Stephanitis pyrioides Scott, was evaluated. Each genotype had a distinct epicuticular lipid composition. The major surface lipid components from all test taxa were n-alkanes and triterpenoids. In the most resistant genotypes [R. canescens Michaux and R. periclymenoides (Michaux) Shinners] ursolic acid, n-hentriacontane, and n-nonacosane were the most abundant epicuticular lipids. The lipids present in largest proportion among all susceptible deciduous genotypes tested were α-amyrin, β-amyrin, and n-nonacosane. The proportions of the lipid components from the same plant of each genotype varied between spring and fall samples. Among classes of lipids, n-alkanes, n-1-alkanols, and triterpenoids had significant correlations with azalea lace bug behavior on host plants. Among individual components, heptadecanoic acid, n-hentriacontane, oleanolic acid, ursolic acid and one unknown compound (with major mass spectra 73/179/192/284/311) were significantly negatively correlated with host plant susceptibility to azalea lace bug, as measured by oviposition, leaf area damaged, egg and nymphal development, and nymphal survivorship. Triacontanol, α-amyrin, β-amyrin, and three unknowns were significantly positively correlated with host plant susceptibility. Acceptance or rejection by azalea lace bug to a particular plant may be mediated by a balance of positively and negatively interpreted sensory signals evoked by plant chemicals. This study indicated that the high levels of resistance observed in R. canescens and R. periclymenoides may be due to the lesser amount or the absence of attractants and stimulants for feeding or oviposition.
Little information is available on cultural requirements for greenhouse production of Tradescantia virginiana L. We tested three plant growth regulators (PGRs) at ascending rates on T. virginiana `Angel Eyes,' `Blue Stone,' and `Red Cloud' in an effort to find appropriate application levels for height suppression. Treatments applied two weeks after transplant. Each PGR was applied once at the following rates: paclobutrazol at 0, 40, 80, 120, or 160 mg·L-1, uniconazole at 0, 15, 30, 45, or 60 mg·L-1, or flurprimidol at 0, 15, 30, 45, 60, or 75 mg·L-1. Repeated measures experimental design and multivariate analysis was used to examine plant responses to PGRs over time. The most effective paclobutrazol rate for adequate height suppression was 120 mg·L-1. Uniconazole at 30 to 45 mg·L-1 and flurprimidol at 45 to 60 mg·L-1 resulted in adequate height control. `Blue Stone' and `Red Cloud' appeared more responsive (greater suppression of height at rates applied) to both uniconazole and flurprimidol than `Angel Eyes.' These results suggest that cultivars respond in a different manner to PGRs applied to them; more compact growth can be obtained for cultivars tested using these suggested rates. Chemical names used: trifuloromethoxy phenyl-5-pyrimidinemethanol (flurprimidol); [(±)-(R*,R*)-ß-((4-chlorophenyl) methyl)-?-(1,1,-dimethylethyl)-1H-1,2,4,-triazole-1-ethanol)] (paclobutrazol); uniconazole.
Despite the popularity of fountain grass (Pennisetum alopecuroides) as a landscape perennial, little research has been conducted on nursery management practices that maximize its overwintering survival and subsequent spring vigor in container production systems. An experiment was conducted to determine the effect of protective covers (a double layer of insulation fabric, a double layer of insulation fabric plus a single sheet of white polyethylene plastic, or no cover), fertilizer application rate (high and low), and substrate moisture content (irrigated when substrate volumetric water content (VWC) fell below 15% and 25%) on the survival rate and vigor of container-grown fountain grass: straight species fountain grass (SFG), ‘Hameln’ fountain grass (HFG), and ‘Little Bunny’ fountain grass (LBFG). Plants were overwintered in a coldframe and were evaluated for survival rate (percent that survived the winter) and vigor (visual rating scale 1 to 5) the following spring. Survival rate and vigor ratings varied among species. However, the highest survival rates (generally 75% or greater) and vigor ratings (generally 3 or greater) were in treatments that used protective covers, though there was not a clear advantage to using white polyethylene in addition to the double layer of insulation fabric. In treatments that used either of the protective covering methods and the high fertilizer application rate, 25% or less of LBFG survived and had vigor ratings of 1.3 or less. In contrast, 75% of LBFG survived when the low fertilizer rate was used in conjunction with either protective covering method. Substrate moisture content only affected the survival rates of SFG and HFG when no protective cover was used, although these survival rates were less than those with covers. These results suggest that protective covers may serve as a tool to minimize winter damage and improve crop quality for the species used in this trial. Because of the varied capacity among these cultivars to tolerate different fertilizer rates and substrate moisture contents, it is recommended that growers use the results of this study as a baseline for conducting site evaluations to determine overwintering techniques that maximize survival and vigor on their facilities.
Nondestructive studies of plant root systems are limited to hydroponic and glass-wall-type growing systems, which are expensive and limit the ways to observe and measure root structures. The following system was adapted from agronomic studies as a convenient, cost-efficient, and sensitive method of monitoring root growth of horticultural crops.
A survey indicated that the landscape maintenance and lawn care industry of the Atlanta metro area was localized in densely populated counties with a high concentration of commercial activity and residential housing. A relatively young age and limited size of most of the firms suggested a lack of barriers to entering the industry, which was supported by gross sales and equipment owned by surveyed companies. Most firms generated no more than $100,000 in sales in 1993 and owned equipment valued at less than $25,000. Most residential accounts were under 10 acres.
A pine tree substrate (PTS), produced by grinding loblolly pine trees (Pinus taeda), offers potential as a viable container substrate for greenhouse crops, but a better understanding of the fertilizer requirements for plant growth in PTS is needed. The purpose of this research was to determine the comparative fertilizer requirements for chrysanthemum (Chrysanthemum ×grandiflora ‘Baton Rouge’) grown in PTS or a commercial peat-lite (PL) substrate. The PTS was prepared by grinding coarse (1-inch × 1-inch × 0.5-inch) pine chips from debarked loblolly pine logs in a hammer mill fitted with 3/16-inch screen. The PL substrate composed of 45% peat, 15% perlite, 15% vermiculite, and 25% bark was used for comparative purposes. Rooted chrysanthemum cuttings were potted in each of the substrates on 15 Oct. 2005 and 12 Apr. 2006 and were glasshouse grown. Plants were fertilized with varying rates of a 20N–4.4P–16.6K-soluble fertilizer ranging from 50 to 400 mg·L−1 nitrogen (N) with each irrigation. Plant dry weights and extractable substrate nutrient levels were determined. In 2005 and 2006, it required about 100 mg·L−1 N more fertilizer for PTS compared to PL to obtain comparable growth. At any particular fertilizer level, substrate electrical conductivity and nutrient levels were higher for PL compared to PTS accounting for the higher fertilizer requirements for PTS. Possible reasons for the lower substrate nutrients levels with PTS are increased nutrient leaching in PTS due to PTS being more porous and having a lower cation exchange capacity than PL, and increased microbial immobilization of N in PTS compared to PL. This research demonstrates that PTS can be used to grow a traditional greenhouse crop if attention is given to fertilizer requirements.
Optimizing growing conditions and, thereby, plant growth reduces the susceptibility of plants to many disease and insect pest problems. Educating lawn or landscape management professionals and homeowners about plant health management reduces the need for chemical intervention. Pesticides combined with N and P fertilizers contribute to water pollution problems in urban areas; thus, it is important to manage the amount, timing, and placement of chemicals and fertilizers. To educate consumers applying pesticides and fertilizers in residential gardens, we must educate the sales representatives and others who interact most closely with consumers. Evidence suggests that knowledge about the effects of chemicals is limited and that warning labels are not read or are ignored. Integrated pest management (IPM) offers alternatives to conventional chemical treatments, but such methods are not used commonly because of their relatively high cost and their uncertain impact on pests. Pest detection methods and using pest-resistant plants in landscapes are simple and, in many cases, readily available approaches to reducing the dependence on chemical use. Research on effective, low-cost IPM methods is essential if chemical use in landscape management is to decrease. Current impediments to reducing the pollution potential of chemicals used in the landscape include the limited number of easily implemented, reliable, and cost-effective alternative pest control methods; underfunding of research on development of alternative pest control measures; limited knowledge of commercial operators, chemical and nursery sales representatives, landscape architects, and the general public concerning available alternatives; reluctance of the nursery industry to produce, and of the landscape architects to specify the use of, pest-resistant plant materials; lack of economic or regulatory incentive for professionals to implement alternatives; inadequate funding for education on the benefits of decreased chemical use; and the necessity of changing consumer definition of unacceptable plant damage. We need to teach homeowners and professionals how to manage irrigation to optimize plant growth; use sound IPM practices for reducing disease, weed, and insect problems; and minimize pollution hazards from fertilizers and pesticides.
Pesticides have been the primary method of pest control for years, and growers depend on them to control insect and disease-causing pests effectively and economically. However, opportunities for reducing the potential pollution arising from the use of pesticides and fertilizers in environmental horticulture are excellent. Greenhouse, nursery, and sod producers are using many of the scouting and cultural practices recommended for reducing the outbreak potential and severity of disease and insect problems. Growers are receptive to alternatives to conventional pesticides, and many already use biorational insecticides. Future research should focus on increasing the effectiveness and availability of these alternatives. Optimizing growing conditions, and thereby plant health, reduces the susceptibility of plants to many disease and insect pest problems. Impediments to reducing the use of conventional pesticides and fertilizers in the environmental horticulture industry include 1) lack of easily implemented, reliable, and cost-effective alternative pest control methods; 2) inadequate funding for research to develop alternatives; 3) lack of sufficient educational or resource information for users on the availability of alternatives; 4) insufficient funding for educating users on implementing alternatives; 5) lack of economic or regulatory incentive for growers to implement alternatives; and 6) limited consumer acceptance of aesthetic damage to plants. Research and broadly defined educational efforts will help alleviate these impediments to reducing potential pollution by the environmental horticulture industry.