Wheeler G. Foshee

Herbicide Combinations in Tomato to Prevent Nutsedge (Cyperus esulentus) Punctures in Plastic Mulch for Multi-Cropping Systems

Yellow nutsedge can readily puncture the plastic mulch used in plasticulture tomato production, compromising the benefits of the mulch and hastening its deterioration. Our objective was to identify a PRE-applied (i.e., under the plastic) treatment to minimize yellow nutsedge puncturing. In a greenhouse study a series of halosulfuron rates were PRE-applied to soil planted with yellow nutsedge tubers. These rates were also applied to established plants but with selective spray contact. Nonlinear regression revealed that the concentration of halosulfuron required to reduce dry weights by 90% (GR90) for PRE-applied halosulfuron was 11.6 g/ha. The GR90 for POST-applied halosulfuron was 17.1, 28.1, and 11.6 g/ha for foliar-only, soil-only and foliar plus soil spray contact, respectively. Thus halosulfuron was more effective as a POST-applied, foliar-contacting treatment. However, soil activity was deemed likely sufficient to suppress plastic puncturing. In a noncrop field study, suppression of puncturing was influenced (P < 0.05) by the rate of both PRE-applied halosulfuron and S-metolachlor. A field study with tomato was conducted to evaluate six selective treatments using plastic mulch, PRE-applied S-metolachlor, and the combination of PRE or PRE/POST-split applications of halosulfuron. Plastic alone increased tomato yield threefold compared with bare ground. The addition of various herbicide programs neither increased nor reduced yield compared with plastic alone. Selected herbicide treatments did reduce mulch puncturing but not to the extent or duration that would allow sequential crops to receive the full benefit of nonpunctured plastic. Nomenclature: Halosulfuron, S-metolachlor, yellow nutsedge, Cyperus esculentus L. CYPES, tomato, Lycopersicon esculentum Mill. ‘Florida 91’

Plastic Mulches and Row Covers on Growth and Production of Summer Squash

ABSTRACT Row covers and colored plastic mulch are used routinely throughout the United States to grow vegetables but are rarely used in conjunction to produce a crop. Summer squash (Cucurbita pepo L.), cv. Prelude II, was grown on an Orangeburg sandy loam soil in Shorter, AL. The summer squash was direct seeded in single rows. The experiment consisted of 12 treatments including: (1) black plastic mulch (BPM)+spunbonded row cover (RC), (2) BPM alone, (3) white plastic mulch (WPM)+RC, (4) WPM alone, (5) red plastic mulch (RPM)+RC, (6) RPM alone, (7) bare soil (BS)+RC, (8) BS alone, (9) silver plastic mulch (SPM)+RC, (10) SPM alone, (11) blue plastic mulch (BLUPM)+RC, and (12) BLUPM alone. Year and mulch color affected all variables, row cover affected plant height and stem diameter, and the mulch color × row cover interaction affected yield variables. Mulch color and year significantly affected air and soil temperatures and row cover significantly affected air temperature. Soil temperatures were more than 5°C lower than air temperatures in all treatments and air temperatures were 2–5°C higher with row covers than without. Increased soil and air temperatures did not always result in yield increases. Colored plastic mulch with or without row covers did not increase early fruit yield in squash. Lack of a mulch/row cover induced temperature effect on yield was attributed to the relatively high mean air temperatures that may have masked treatment temperature effects.

Yellow Nutsedge (Cyperus esculentus) Control and Tomato Response to Application Methods of Drip-Applied Herbicides in Polyethylene-Mulched Tomato

Abstract Drip-applied herbicides provide farmers with a more timely and cost-effective approach for applying PRE herbicides; however, herbicide movement is often limited. Field studies were conducted evaluating drip-application methods for applying PRE herbicides under polyethylene-mulched beds on yellow nutsedge punctures and the corresponding responses of a tomato crop (height and yield). The experiment was a factorial treatment arrangement of three drip application methods and three PRE-applied herbicides [halosulfuron (54 g ai ha−1), S-metolachlor (1.4 kg ha−1), and fomesafen (280 g ha−1)]. Herbicides were applied either immediately following saturation of the planting beds (method A), over an extended period while saturating the beds (method B), or prior to bed saturation (method C). Additional treatments included a commercial standard (S-metolachlor sprayed to the bed surface prior to mulch application) and a nontreated control (polyethylene mulch only). Drip-applied fomesafen, halosulfuron, and S-metolachlor provided similar control of yellow nutsedge, produced comparable yields, and failed to elicit any negative growth responses when compared to our commercial standard. With the exception of nutsedge punctures counted 56 DAT, application method did not influenced measurable outcomes. At 56 DAT nutsedge punctures were significantly lower in treatments applied by method B compared to those applied with method A. Nomenclature: Fomesafen; halosulfuron; S-metolachlor; yellow nutsedge, Cyperus esculentus L; tomato, Solanum lycopersicum L Resumen Los herbicidas aplicados en sistemas de riego por goteo brindan a los productores un sistema más barato y flexible para la aplicación de herbicidas PRE en diferentes momentos. Sin embargo, el movimiento del herbicida es a menudo limitado. Se realizaron estudios de campo para evaluar métodos de aplicación de herbicidas por goteo para aplicar herbicidas PRE bajo camas con coberturas de polyethylene para el control de la perforación causada por Cyperus esculentus y la correspondiente respuesta del cultivo de tomate (altura y rendimiento). El experimento fue un arreglo factorial de tratamientos de tres métodos de aplicación por goteo y tres herbicidas aplicados PRE [halosulfuron (54 g ai ha−1), S-metolachlor (1.4 kg ha−1), y fomesafen (280 g ha−1)]. Los herbicidas fueron aplicados ya fuera inmediatamente después de saturar las camas de siembra (método A), a lo largo de un período extendido durante la saturación de las camas (método B), o antes de la saturación de las camas (método C). Tratamientos adicionales incluyeron un estándar comercial (S-metolachlor asperjado sobre la cama de siembra antes de la colocación de la cobertura) y un testigo sin tratamiento (solamente cobertura de polyethylene). Fomesafen, halosulfuron, y S-metolachlor aplicados por goteo brindaron un control similar de C. esculentus, produjeron rendimientos comparables, y no generaron respuestas negativas en el crecimiento del cultivo cuando se compararon con nuestro estándar comercial. Con la excepción del número de perforaciones causadas por C. esculentus contadas 56 DAT, el método de aplicación no influenció ninguna de los factores medidos. A 56 DAT, las perforaciones de C. esculentus fueron significativamente menores en tratamientos aplicados con el método B al compararse con los del método A.

Comparison of Preemergence and Postemergence Weed Control Systems in Newly Established Pecan

Six weed control programs with and without irrigation were investigated in a newly established pecan orchard. Irrigation increased crown diameter growth in only one of seven growing seasons but increased nut yield an average of 35% in the first two bearing years. Weed control program significantly influenced crown diameter beginning in the fourth growing season and continued through season six while also impacting final crown diameter. The use of postemergence (POST) herbicides increased crown diameter a minimum 4 mm vs. preemergence (PRE) herbicides. Mowing neither increased nor decreased crown diameter when used with herbicides; however, when used solely, crown diameter was 29% less. Highest growth rates were obtained with a combination PRE plus POST weed management system. Nut yields were closely linked to growth data. No differences in nut yield were observed between PRE- or POST-herbicide programs alone or in combination with mowing. Mowing alone decreased nut yield 57% vs. herbicide-based approaches. A combination PRE- plus POST-weed control program increased yield 38% vs. all other treatments. Nomenclature: Pecan, Carya illinoinensis (Wang.) K. Koch var. ‘Desirable’.

Nitrogen Requirements for Sweetpotato Following a Crimson Clover Cover Crop

Sweetpotato [Ipomoea batatas (L.) Lam.] is an economically important crop in the southeastern United States, and sustainable production practices that include reducing fertilizer costs and improving soil organic matter are needed. Field studies were conducted in the Spring of 2007 and 2008 to evaluate nitrogen fertilization requirements of sweetpotato. Treatments of 0, 50, and 101 kg·ha−1 nitrogen (from ammonium nitrate applied preplant broadcast) were applied following a crimson clover (Trifolium incarnatum L.) cover crop along with a conventional no cover crop treatment using 101 kg·ha−1 N (from ammonium nitrate). Sweetpotato yields for all rates of N fertilizer following the cover crop were similar (for ‘Beauregard’ in 2007) or greater (for ‘Xushu 18’ in 2008) than yields from plants grown using the conventional treatment. Percentage of dry matter of storage roots was not affected by treatment. Nitrogen fertilization can be reduced or eliminated when sweetpotatoes are produced following a crimson clover winter cover crop.

Pulsed electric field effects on the germination rate of yellow nutsedge seeds

Pulsed electric field to treat seeds is an alternate method to the chemical treatment to control the weeds in the field. In this study yellow nutsedge seeds were subjected to series of repetitive pulsed electric field and the germination rate of the seeds after the treatment with respect to the non-treated seeds were studied. The seeds used in the experiment were air dried before they were exposed to repetitive pulsed electric fields. The pulse generator is built in-house, with an average pulse width of few microseconds and peak voltage of up-to25KV. In this study only the amplitude of the pulse and the repetition rate was used as the parameters on the germination rate of the seeds. The data obtained from the seeds, which are exposed to series of Pulsed Electric Fields resulted in the decrease in the percent seedling emergence for Yellow Nutsedge seeds in comparison to the non-exposed seeds. A replicated study and better understanding of this experiment may lead to a method for better non chemical weed control. This study intends to present the effects of pulsed electric fields on the seeds of yellow nutsedge and establish the feasibility to use such an approach for weed control, to decrease their germination rate in the field.

Management of Plum Curculio and Catfacing Insects on Peaches in Central Alabama: Standard Crop Stage–Based vs. Integrated Pest Management–Based Approaches

ABSTRACT Plum curculio, tarnished plant bug, brown stink bug, and green stink bug are the major insect pests causing fruit damage on peaches grown in the southeastern United States. Insect management aids, monitoring techniques, predictive models, and action thresholds for southeastern peaches are either lacking or they are not robust enough to facilitate industry acceptance of as-needed insecticide applications during the growing season (Horton et al., 2003). In this 3-year study, we compared two approaches to scheduling insecticide applications for control of these pests on three peach cultivars in an established central Alabama orchard: 1) an industry standard, representative of prevailing practice in the southeastern United States, which consisted of scheduled insecticide applications timed to coincide with crop stage; and 2) an integrated pest management (IPM) treatment, which employed limited prescheduled insecticide applications timed to coincide with the crops developmental stage, supplemented with as-needed insecticide applications when preestablished action thresholds were reached. Percentage of insect-damaged fruit from trees under the IPM treatment was similar to, or in some cases greater or less than, that of fruit from trees receiving the standard treatment. Depending on the year, the same or fewer insecticide applications were made under the IPM treatment compared with the standard treatment. The IPM treatment came close to providing acceptable levels of plum curculio control with the early-season cultivar Correll but not with the mid- and late-season cultivars Sunland and Biscoe.

Pulsed electric field studies of bio-dielectrics

Chemical weed control accounts for oyer /spl Bscr/ in costs to the American farmer. Non-chemical alternatives offer many advantages such as protecting the environment and safety for applicators. Studies have shown that high voltage, pulsed electric field (PEF) treatment of biodielectrics is an effective method to inactivate micro-organisms and bacteria. Therefore, the PEF technology might be used as an effective alternative to chemical weed control. In this work, we have studied the breakdown characteristics of weed seeds using single and repetitive pulsed electric fields. Breakdown of seeds as a function of various parameters of the pulsed system such as its duration, rise/fall time, repetition rate, and field strength, are studied. Two types of weed seeds, namely yellow foxtail and smallflower morningglory, were used in the experiment. Preliminary results suggest that the PEF method can reduce the percent germination of the yellow foxtail. Conversely, the smallflower morningglory had increased percent germination. This trend is most likely due to the presence or absence of a hardened seed coat of which the smallflower morninglory possesses.

Mixed Municipal Solid Waste Compost as a Soil Amendment on Yield and Heavy Metal Accumulation in Okra and Watermelon

ABSTRACT Application of compost in horticultural crops has the potential to provide many benefits and yet there are concerns regarding accumulation of heavy metals in the crop and on human health. Effects of amending soil with compost made from mixed municipal solid waste (MSW) on yield of okra (Abelmoschus esculentus L.) and watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] and on heavy metal concentrations (Cd, Cu, Cr, Ni, Pb, and Zn) in pods of okra and pulp and juice of watermelon were investigated. Four MSW compost rates were applied, 25, 50, 75, and 100 Mg·ha−1, and compared to a non-amended control with no compost application. Addition of MSWC increased yield of okra and weight of watermelons over the control. There were no differences among treatments in heavy metal concentrations in okra pods, watermelon pulp, or juice.

Seedling Emergence of Smallflower Morningglory and Green Foxtail Subjected to a Pulsed Electric Field

ABSTRACT Non-chemical approaches to weed control as possible methyl bromide alternatives, or for organic production, are needed in vegetable production. Effects of pulsed electric fields generated by a DC breakdown event and from a Blunlein transmission line type generator were tested to ascertain their effects on seedling emergence of Smallflower Morningglory [Jacquemontia tamnifolia(L.) Briseb.] and Green Foxtail [Setaria viridis(L.) Beauv.]. Seeds were air-dried and exposed to single and repetitive pulsed electric fields. To determine the effect of these systems the parameters of the pulsed system such as duration, rise/ fall time, repetition rate, and field strength, were tested. The DC breakdown results indicated a decrease in percent seedling emergence for Green Foxtail and an increase in seedling emergence for Smallflower Morningglory. A replicated study was conducted with a 50 ns pulse generator with an average of 59 kV output. The pulsed electric field method caused a small increase in seedling emergence from air-dried seed of Smallflower Morningglory, possibly due to disruption of the hard seed coat of this species. A better understanding of the application of a pulsed electric field may lead to a method for non-chemical weed control.