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Bruce P. Bordelon and Stephen C. Weller

Use of in-row cover crops for weed management in first-year vineyards was investigated in two studies. In the first study, rye (Secale cereal L. 'Wheeler') was fall-planted, overwintered, then managed by three methods before vine planting. Rye was either herbicide-desiccated with glyphosate and left on the surface as a mulch, mowed, or incorporated into the soil (cultivated). Weed density and growth of grapevines (Vitis spp.) were evaluated. Herbicide desiccation was superior to the other methods for weed suppression, with weed densities 3 to 8 times lower than for mowed or cultivated plots. Vine growth was similar among treatments, but the trend was for more shoot growth with lower weed density. In a second study, four cover crops, rye, wheat (Triticum aestivum L. 'Cardinal'), oats (Avena sativa L. 'Ogle'), and hairy vetch (Vicia villosa Roth), were compared. Wheat and rye were fall- and spring-planted, and oats and vetch were spring-planted, then desiccated with herbicides (glyphosate or sethoxydim) after vine planting and compared to weed-free and weedy control plots for weed suppression and grapevine growth. Cover crops provided 27% to 95% reduction in weed biomass compared to weedy control plots. Total vine dry mass was highest in weed-free control plots, was reduced 54% to 77% in the cover crop plots, and was reduced 81% in the weedy control. Fall-planted wheat and rye and spring-planted rye plots produced the highest vine dry mass among cover crop treatments. Spring-planted rye provided the best combination of weed suppression and vine growth. Chemical names used: N-(phosphonomethyl) glycine (glyphosate isopropylamine salt); 2-[l-(ethoxyimino)butyl]5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one (sethoxydim).

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Bruce P. Bordelon and Stephen C. Weller

Four cover crops were evaluated for weed control and effects on first-year vine growth. Winter wheat (cv. Cardinal), rye (cv. Wheeler), oats (cv. Ogle), and hairy vetch (no cultivar name) were either fall- or spring-planted and compared to cultivated and weedy control plots. Cover crop and weed biomass dry weight was collected twice during the growing season. Vines (Vitis labrusca cv. Steuben) were planted in the spring and destructively sampled at the end of the growing season for analysis of leaf area, leaf number, shoot length., shoot number, top growth dry weight, and root system dry weight. None of the vines in cover crop treatments had growth as good as vines in the weed-free check. Vines in the best cover crop treatments had ≈70% as much leaf area, 75% as many leaves, 50% as much shoot dry weight, and 40% as much root dry weight as vines in the weed-free check. Cover crop biomass dry weight and vine growth was greater in fall-planted plots than in spring-planted plots. Despite low cover crop biomass dry weight, spring-planted plots had few weeds (low weed biomass dry weight). However, vine growth in spring-planted plots was not significantly different than vine growth in the weedy check.

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Charleson R Poovaiah, Stephen C Weller and Matthew A Jenks

An in vitro shoot regeneration procedure was developed for native spearmint (Mentha spicata L.) using internodal explants. Shoot regeneration from internodes was evaluated on Murashige and Skoog (MS) media supplemented with individual cytokinins thidiazuron (TDZ), benzylaminopurine (BA), kinetin (KT), or zeatin (ZT) or various pair wise combinations of these. The highest regeneration was achieved by the second internode on a medium containing MS basal salts, B5 vitamins, 10% coconut water, 1.0 mg·L–1 TDZ, 2.5 mg·L–1 ZT, and solidified with 0.2% phytagel. Unlike previous protocols this medium does not need sub culturing and produces elongated shoots in 4 weeks, rather than 6 weeks. Maximum number of shoots (36 per explant after 4 weeks) was observed when internodes from 2-week-old stock plants were used as explant source. The shoots were removed and roots were initiated on medium containing MS basal salts, 0.4 mg·L–1 thiamine-HCL, 100 mg·L–1 myo-inositol, 7.5 g·L–1 agar and 0.01 mg·L–1 ∝-napthaleneacetic acid (NAA) and then plants were transferred to the greenhouse 2 weeks after root initiation, where 100% of the plantlets developed into healthy plants.

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James W. Julian, Glenn H. Sullivan and Stephen C. Weller

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David R. Byrnes, Fekadu F. Dinssa, Stephen C. Weller and James E. Simon

Vegetable amaranth (Amaranthus sp.), a leafy vegetable crop consumed around the world, is actively promoted as a source of essential micronutrients to at-risk populations. Such promotion makes micronutrient content essential to the underlying value of this crop. However, the extent to which micronutrient content varies by effect of genotype is not clear, leaving breeders uninformed on how to prioritize micronutrient contents as the criteria for selection among other performance parameters. A total of 32 entries across seven Amaranthus species were field-grown and analyzed for Fe, Mg, Ca, Zn, yield, height, and canopy spread comprising 20 entries at New Jersey in 2013; 12 entries at Arusha, Tanzania, in 2014; and 20 entries at New Jersey in 2015. The genotype effect was significant in all trials for Fe, Mg, Ca, Zn, total yield, marketable yield, height, and canopy spread. The Fe content range was above and below the breeding target of 4.2 mg/100 g Fe in all environments except for New Jersey 2015, where all entries were found to accumulate in levels below the target. All entries in each of the environments contained levels of Ca and Mg above breeding targets, 300 mg/100 g Ca and 90 mg/100 g Mg. None of the entries in any environment met the Zn breeding target of 4.5 mg/100 g Zn.

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Farah MG Héraux, Steven G. Hallett, K.G. Ragothama and Stephen C. Weller

Trichoderma virens (Gliocladium virens) (Miller et al.) von Arx is a soilborne fungus with a high degree of rhizosphere competence that produces a potent herbicidal compound, viridiol, and therefore has potential for development as a bioherbicide. We investigated the possibility of using composted chicken manure (CCM) as a medium for the production and deployment of T. virens. We chose CCM since the safe disposal of chicken manure presents significant logistic problems, and composted manures, as well as serving as an organic source of nitrogen, have been shown to support the activity of other biological control agents. Composted chicken manure supported the growth of T. virens and the rapid production of high concentrations of viridiol, but only when it was supplemented with large quantities of nutrients, including sucrose (16% w/w). Viridiol was not stable when stored in CCM, with a rapid decline in viridiol concentrations observed in T. virens-inoculated CCM cultures. Clearly, a cheaper alternative to sucrose is required as a carbon source for T. virens in CCM or similar media, and effective storage methods would need to be found for a T. virens-based bioherbicide product. Importantly, CCM did not need to be sterilized to support the growth of T. virens and its concomitant production of viridiol, suggesting that on-farm production systems may be feasible. Trichoderma virens-colonized CCM reduced the emergence and seedling growth of redroot pigweed (Amaranthus retroflexus L.) in a greenhouse experiment and dramatically reduced the emergence of a mixed community of broadleaf weeds in the field.

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Steven D. Siegelin, Darrel D. Daniels, Merrill A. Ross and Stephen C. Weller

This study was conducted in 1993 and 1994 to determine if nicosulfuron or primisulfuron had any adverse effects on ear or whole-plant development. Factors considered were cultivar, herbicide, rate, and timing of application. Four sweet corn cultivars: `More' (su), `Calico Belle' (se), and `Frontier' and `Challenger' (sh2) were evaluated for foliar injury, plant vigor, plant height (1994 only), ear injury, and yield. Nicosulfuron and primisulfuron were applied at two rates: the labeled rate (x) of 35 g a.i./ha and 40 g a.i./ha, respectively, and at the 2x rate. Herbicides were applied early postemergence at V2 (corn height 10–15 cm) or late postemergence at V7 (corn height 30–50 cm). Plant foliar injury ratings, ear injury ratings, number of ears, number of injured ears, and yields were collected. Ears with injury were described as pinched. There was a constriction of the cob, caused by a reduction in kernel row number, ranging from two to eight rows lost. Sweet corn cultivars varied in their response to nicosulfuron and primisulfuron. Timing of application had a greater impact on ear injury than did the rate. Applications at the V7 stage caused more severe ear injury than application at the V2 stage. Ear injury was more severe in nicosulfuron treatments than primisulfuron treatments. Height reductions were caused by both compounds at both applications, with primisulfuron causing greater stunting. Primisulfuron caused more severe foliar injury.