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Robert O. Miller, Steven E. Newman, and Janice Kotuby-Amacher

The accuracy of soil and plant analytical results are occasionally called into question by laboratory clientele. Although laboratories generally conduct internal quality assurance procedures, there are few external performance testing programs for the industry. In 1994, a proficiency testing program was initiated for soil and plant samples for agricultural laboratories in the western United States to provide an external quality control for the lab industry. The program involves the quarterly exchange of soil and plant samples on which soil salinity, soil fertility, and plant nutrition analyses are conducted. One hundred laboratories are annually enrolled in the program from 24 states and Canadian provinces. Results of 3 years of the program indicate soil nitrate, soil pH, extractable potassium, soil and organic matter are reproducible within 10% between laboratories. Soil-extractable phosphorus (by five methods), soil-extractable boron, and soluble chloride were only reproducible within 15% to 20% between laboratories. Plant nitrogen and phosphorus results were consistent across samples, laboratories, and methods. Variability in plant nitrate increased with decreasing tissue concentrations. Overall accuracy and precision of reported results, based on the use of NIST certified reference botanical samples, were excellent for N, P, K, Ca, and Cu. Generally, for any given analysis, the results of ≈10% of the laboratories exceed two standard deviations from the mean. Overall, significant improvement was noted in the laboratory industry proficiency through the course of the program.

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April D. Edwards, Steven E. Newman, and Adolph J. Laiche

Kenaf (Hibiscus cannabinus) is an alternative fiber crop being grown in Mississippi that maybe used as a tree-less fiber substitute for making paper. A by-product in this process is the pithy light-weight fiber core. The objective of this study was to examine the chemical and physical properties of kenaf fiber core as a medium component in growing woody ornamentals and compare to pine bark. Comparisons of media in which Ilex crenata `Cherokee' and Rhodoendron eirocarpum `Wakabuisi' were grown were made. The physical and chemical properties including bulk density, total pore space, water retention, pH and soluble salt concentrations were determined. Aged kenaf had lower pH values than fresh and both aged and fresh kenaf had higher pH values than pine bark. The total pore space of kenaf was lower than the pore space of pine bark. At the termination of the study, the kenaf media had considerable shrinkage, which was considered unsuitable for a long-term crop.

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Michelle L. Jones, Eun-Sun Kim, and Steven E. Newman

Geraniums are sensitive to ethylene during shipping and respond by abscising their petals. Treatment of stock plants with ethylene (ethephon) in order to increase cutting yield resulted in earlier flowering in Pelargonium × hortorum `Kim' and `Veronica', but did not result in increased susceptibility to petal abscission following exposure to 1.0 μL·L-1 ethylene. Treatment of `Kim', `Veronica', `Fox', and `Cotton Candy' with 1.0 μL·L-1 ethylene resulted in increased petal abscission within one hour, with `Fox' being the most sensitive and `Kim' the least. Pretreatment of florets with 1-MCP for 3, 6, 12, or 24 hours at concentrations of 0.1 or 1.0 μL·L-1 decreased petal abscission in all cultivars following exposure to 1.0 μL·L-1 ethylene. Treatment with 0.1 μL·L-1 1-MCP for 1 hour reduced petal abscission rates in ethylene treated florets to that of non-ethylene treated controls in all cultivars except Fox. `Fox' florets, which are more sensitive to ethylene, required 12 to 24 hours of exposure to 1-MCP to reduce petal abscission rates to that of control flowers. Pretreatment of geranium plants with 1-MCP can be used to reduce petal shattering during shipping. Chemical names used: 2-chloroethanephosphonic acid (ethephon); 1-methylcyclopropene (1-MCP).

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

A formulation of quaternary benzophenathridine alkaloids (QBA) was combined with piperalin as a tank mix. The QBA was applied at 150 mg/L and piperalin, at the labeled rate, was applied as a spray application to greenhouse roses infected with Sphaerotheca pannosa var. rosae (powdery mildew). Copper sulfate pentahydrate and fenarimol were also applied to mildew-infected plants within the same greenhouse at their respective label rates for comparison. Initial infection for the QBA/piperalin combination spray was 45% of the leaflet surface area, 3 days after application the infection was reduced to 10%, 6 days after application infection was reduced to 5%, and 14 days after application the infection remained at 5%. Initial infection for a QBA application without piperalin was 25% of the leaflet surface area. Three days after application, the infection was reduced to 15%; 6 days after application the infection remained at 15%; and 14 days after application, the infection was reduced to 10%. The data reveals that the QBA/piperalin combination gives a short-term as well as a long-term fungicidal and fungistatic activity.

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Karen L. Panter, Steven E. Newman, and Michael J. Roll

Catharanthus roseus plants were grown in three media, each containing one of two by-products of shredded waste tires. The media were no. 1) 1 rubber*: 1 peat moss, no. 2) 1 rubber*: 1 vermiculite: 2 peat moss, and no. 3) 2 rubber*: 1 vermiculite: 1 peat moss (by volume) where rubber* indicates either 0.6 cm shredded rubber or a fibrous by-product. Control plants were grown in 1 peatmoss: 1 rockwool and 1 vermiculite: 1 peatmoss (by volume). Catharanthus roseus cv. Peppermint Cooler plants were grown for 7 weeks in 10-cm containers at a commercial Denver-area greenhouse. Data taken included plant heights, plant widths, flowers per stem, and dry weights. Visually, plants grown in the no. 2 mix, with either fiber or 0.6-cm rubber, were similar to the controls and superior to the other two mixes. Ending plant heights were similar among the two controls and no. 2 with fiber and were taller than all other combinations. Flower numbers were greater in the 1 rockwool: 1 peat moss control and no. 2 mix with fiber than any other treatment. The same was true for stem number and dry weight. Results indicate that the no. 2 mix of 1 fiber: 1 vermiculite: 2 peatmoss has potential for container crop production.

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

There are many naturally occurring substances that have the potential to be adapted to modern pest control chemistry. Azadirachtin, an insect growth regulator, is one such naturally occurring compound that has been widely accepted in insect pest management. Quartenary benzophenanthridine alkaloids (QBAs) are known to be effective in the control of crop damaging fungal diseases. QBAs can be isolated from plants in the Papaveraceae. Extracts of Macleaya cordata, a species rich in QBAs, were formulated at 150 mg·L–1 QBA for spray application to greenhouse roses infected with Sphaerotheca pannosa var. rosae (powdery mildew). The QBA formulation was applied at 10-day intervals. Copper sulfate pentahydrate (Phyton27), piperalin (Pipron), and fenarimol (Rubigan) were also applied to mildew infected plants within the same greenhouse at their respective label rates for comparison. One day after treatment, the mildew infection was reduced 50% by QBA, whereas fenarimol, copper sulfate pentahydrate, and piperalin reduced the infection 50%, 75%, and 80%, respectively. Nine days after application, the mildew infection of QBA treated plants was less than 5% of the leaflet surface area. QBAs have the potential to be developed as a biorational fungicide for greenhouse use with both fungicidal and fungistatic activity.

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Xiaomei Zhao, William L. Kingery, and Steven E. Newman

Media blends containing 25%, 40%, and 50% shredded tire rubber were compared to two commercial media, Baccto Grower's Mix and Ball Peat-Lite Mix, to evaluate its potential as a container medium amendment for container-grown greenhouse plants. Salvia splendens `Red Hot Sally' and Vinca rosea `Cooler Peppermint' grown in 25% rubber were marketable with growth similar to or superior to those grown in the commercial media. Exacum affine `Little Champ', Vinca rosea `Cooler Grape', Tagetes erecta `Discovery Yellow', and Begonia semperflorens `Vodka' grown in 25% rubber were of marginally acceptable quality. Plants grown in 40% or more rubber were shorter and chlorotic compared to those in the commercial media. Exacum affine grown in 40% or more rubber contained high levels of zinc, which may have been linked to the chlorosis and growth reduction. Rubber reduced media water-holding capacity, while cation exchange capacity and pH were not affected.

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Steven E. Newman, Jesse R. Quarrels, Jacobo Cáceres, and William E. Batson

Poinsettia growers generally apply fungicide drenches to circumvent any potential problems corn soil-borne pathogens. This involves a considerable expense in chemical purchase and exposes the handler to risk. A potential biological control organism in commercial production is Gliocladium virens and is being marketed under the trade name GlioGard. This fungal organism is pathogenic towards other fungi including Rhizocotonia solani and Pythium. Two cultivars of poinsettia `Freedom' and `Gutbier V-14 Glory' were planted into Metro 366 medium, half colonized with 0.9 kg·m-3 GlioGard and half not. Half of the rooted cuttings were planted at the standard depth and half planted deep (3 cm). No additional fungicide treatment was made. Those plants transplanted normally without GlioGard had 70-85% survival where those treated with GlioGard had 75-95% survival.

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April D. Edwards, Steven E. Newman, Frank B. Matta, and Adolph J. Laiche

During recent freezes in the mid-south, crape myrtles have suffered severe freeze damage. Some increased levels of cold hardiness have been observed in the National Arboretum crape myrtle releases, but the degree of tolerance has not been documented. The relative cold hardiness of five hybrid crape myrtle cultivars `Muskogee', `Natchez', `Osage', `Tuskegee' and `Yuma' was determined using differential thermal analysis. Stem samples were collected from established trees at two locations, Poplarville, Zone 8 and Starkville, Zone 7 once per month from October through April. Freezing point suppression was determined from five samples from each cultivar and location. Observed exotherms ranged from -7C to -13C.