The increasing perception by consumers that organic food tastes better and is healthier continues to expand the demand for organically produced crops. The objective of these experiments was to investigate the impact of different weed control systems on yields of watermelon (Citrullus lanatus var. lanatus) varieties grown organically. Six watermelon varieties were transplanted at two locations (Lane and Center Point, Okla.). The six varieties included three seeded varieties (`Early Moonbeam', `Sugar Baby', and `Allsweet') and three seedless varieties (`Triple Crown', `Triple Prize', and `Triple Star'). The weed control system at Lane utilized black plastic mulch on the crop row, while the area between rows was cultivated to control weeds. The no-till organic system at Center Point used a mowed rye and vetch cover crop, hand weeding, and vinegar (5% acetic acid) for weed control. When averaged across watermelon varieties, Lane produced significantly more fruit per plant (4.2 vs. 2.3 fruit/plant), greater marketable yields (16.0 vs. 8.4 kg/plants), and higher average marketable weight per fruit (6.1 vs. 4.0 kg) than at Center Point. When comparing locations, four of six varieties had significantly greater number of fruit per plant and higher marketable yields at Lane than at Center Point. Except for `Early Moonbeam', all other varieties produced significantly heavier fruit at Lane than at Center Point. In contrast, the Center Point location produced a greater percentage of marketable fruit for all varieties except `Allsweet'. Fruit quality (lycopene and °Brix) was as good or greater when harvested from the weedier Center Point location.
Charles L. Webber III, Angela R. Davis, James W. Shrefler, Penelope Perkins-Veazie, Vincent M. Russo, and Jonathan V. Edelson
Paulus P. Shelby Jr., David L. Coffey, G. Neil Rhodes Jr., and Larry S. Jeffery
Field studies were conducted in 1983 and 1984 to evaluate the feasibility of growing fresh-market tomatoes (Lycopersicon esculentum Mill. ‘Floradade’) in no-tillage or conventional tillage systems and to evaluate the efficacy of postemergence herbicides under both tillage systems. In 1983, marketable fruit yields in no-tillage were nearly twice those from conventional tillage. In 1984, there were no statistical differences in marketable yields among herbicide treatments or between tillage systems. Yields were higher in 1984 than in 1983, largely due to more favorable growing conditions. In both years, metribuzin provided good broadleaf weed control. In 1983, annual grasses were better controlled in no-tillage with a sequential metribuzin application for fluazifop following metribuzin than with a single metribuzin application. Marketable yields were highest in plots where annual grasses were adequately controlled. Sequential metribuzin applications provided good broadleaf weed control and postemergence grass herbicides each provided excellent annual grass control in 1984. Chemical names used: (±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid (fluazifop); 4-amino-6-(1,1-diemthylethyl)-3-(methyIthio)-1,2,4-triazin-5(4H)-one (metribuzin).
Fumiomi Takeda, D. Michael Glenn, and Thomas Tworkoski
Three experiments were performed to determine the effect of amending the soil surface layer and mulching with hydrophobic kaolin particle on weeds and blackberry (Rubus subgenus Rubus Watson) plants. In the first study a processed kaolin material (product M-96-018, Engelhard Corporation, Iselin, N.J.), was incorporated in August into the top 3 cm of freshly roto-tilled field that had been in pasture the previous 5 years. The following spring, dry weight of weed vegetation in the control treatment was 219 g·m–2 and was significantly higher (P = 0.05) than the 24 g·m–2 harvested from the treated soil. In two other studies, planting holes for blackberry transplants were either 1) pre- or postplant mulched with a 2- or 4-cm layer of 5% or 10% hydrophobic kaolin in field soil (w/w), or 2) postplant treated with a) napropamide, b) corn gluten meal, c) a product comprised of hydrous kaolin, cotton seed oil, and calcium chloride in water (KOL), d) hand weeded, or e) left untreated. Although untreated plots had 100% weed cover by the end of July, herbicide treatments, 4-cm deposition of hydrophobic kaolin particle/soil mulch, and KOL all suppressed weeds the entire establishment year. Preplant application of hydrophobic kaolin mulch and postplant application of KOL reduced blackberry growth and killed transplants, respectively. In year 2, blackberry plants produced more primocanes that were on average 10-cm taller in weed-free plots (herbicide, 4-cm kaolin soil mulch, and mechanical weeding) than in weedy plots (control and 2-cm kaolin soil mulch). In year 3, yield was significantly lower in control plots (1.5 kg/plant) than in plots that were treated with napropamide and 2- and 4-cm hydrophobic kaolin mulch, or hand weeded during the establishment year (4 kg/plant). The results showed that 4-cm hydrophobic kaolin mulch applied after planting can suppress weeds without affecting blackberry productivity. These kaolin products are excellent additions to the arsenal of tools for managing weeds in horticultural crops.
Bonnie L. Appleton and Jeffrey F. Derr
1 Dept. of Horticulture. 2 Dept. of Plant Pathology, Physiology, and Weed Science. Use of trade names in this publication is solely for identification. No endorsement of the products named is implied by VPI & SU. The cost of publishing this
Charlotte Herman, David Larson, and Emily Hoover
29 POSTER SESSION 3 Weed Control/Cross-Commodity
Angela K. Tedesco, Gail R. Nonnecke, Nick E. Christians, John J. Obrycki, and Mark L. Gleason
Field plots of four production systems of `Tristar' dayneutral and `Earliglow' June-bearing strawberry (Fragaria ×ananassa Duch.), established in 1993, included conventional practices (CONV), integrated crop management practices (ICM), organic practices using granulated corn gluten meal, a natural weed control product, (ORG-CGM), and organic practices using a natural turkey manure product (ORG-TM). `Earliglow' total yield from CONV plots in 1994 was similar to ICM and ORG-CGM, but greater than ORG-TM. Average berry weight and marketable yield were greater in the CONV system than both organic systems. CONV, ICM, and ORG-CGM plots had more runners and daughter plants than ORG-TM. Plots with CONV herbicide treatments were similar to ICM and ORG-CGM for percentage weed cover 1 month after renovation. `Tristar' crown number, crown and root dry weights, yield, and berry number were reduced when plants were grown under straw mulch in ORG-CGM and ORG-TM compared to CONV and ICM plots with polyethylene mulch.
J. M. Kennedy, R. E. Talbert, and J. R. Morris
Midsummer grapehoeing following spring application of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] or simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] plus paraquat (1,1’-dimethyl-4,4’-bipyridinium ion) adequately controlled weeds growing in grapes (Vitis labrusca L.). When grapehoeing was used to control grape root borer [(Vitacea polistiformis Harris) lower initial rates of preemergence herbicide could be used. An additional half-rate of herbicide was required after grapehoeing to maintain weed control through the fall. Plots not grapehoed were almost completely weed free following a glyphosate [N-(phosphonomethyl)glycine] treatment. Injury to grapes the following spring was associated with fall glyphosate applications where low hanging foliage, that had not been removed, intercepted the spray. Glyphosate was most effective and paraquat more effective than dinoseb (2-sec-buty1-4,6-dinitrophenol) plus diesel fuel for postemergence control of weeds in grapes. Preemergence herbicides, napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide], norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone], oxadiazon [2-tert-buty1-4-(2,4-dichloro-5-isopropoxyphenyl)-∆2-l,3,4-oxadiazolin-5-one], oryzalin (3,5-dinitro-N 4,N 4-dipropylsulfanilamide), and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene], were effective as residual type treatments.
James E. Klett and David Staats
Herbicides were applied to container grown landscape plants and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. Three preemergent herbicides were applied including: Oxadiazon (Ronstar) at 4.54 and 9.08 kg/ha, Oxyfluorfen + Oryzalin (Rout) at 3.41 and 6.81 kg/ha and Oryzalin (Surflan) at 2.27 and 4.54 kg/ha. There was also a weedy and non-weedy control. The plant species included: Syringa vulgaris (Common Lilac), Wisteria sinensis (Chinese Wisteria), Phlox paniculata (Garden Phlox) and Dahlia hybrid (Garden Dahlia). They were all grown in number one containers in a media of soil, spaghnum peat moss, and plaster sand (1:2:1 by volume). All herbicides tested controlled weeds effectively with no phytotoxicity except with Phlox paniculata. Oryzalin resulted in a phytotoxic effect on Phlox paniculata at both the 1x and 2x rates.
James Klett*, Dave Staats, and Matt Rogoyski
During the 2003 season, preemergence herbicide was applied to twelve container grown herbaceous perennials and woody plants and evaluated for weed control, phytotoxicity, and effect on plant growth. The herbicide and rates were: Flumioxazin (Broadstar) 113.5 g (label rate), 227 g and 454 g a.i./A. Herbicides were applied to Buxus microphylla `Winter Gem', Cytisus purgans `Spanish Gold', Festuca ovina glauca `Elijah Blue', Hakonechloa macra `Aureola', Lonicera tatarica `Arnold Red', Pachysandra terminalis `Green Sheen', Hydrangea arborescens `Annabelle', Mahonia aquifolium, Phalaris arundinacea `Picta', Carex buchananii, Cerastium tomentosum, and Achillea millefolium `Red Beauty'. Weed control was excellent at all rates and controlled at least 99% of all weeds. No phytotoxicity symptoms were apparent on Mahonia, Buxus, Cytisus, Festuca, Hakonechloa, Pachysandra or Phlaris. Phytotoxicity resulted on some of the other plants. Carex had smaller plants (dry weights) at all rates. Cerastium had severe phytotoxicty at the 227 g and 454 g rates and moderate stunting at the recommended label rate, 113.5 g. Hydrangea became chlorotic and stunted at the 113.5 g rate and some fatal toxicity ocurred at the 227 g and 454 g rates. Phytotoxicity resulted on Lonicera at all rates and ranged from mild chlorosis in leaf veins (113.5 g rate) to plant death (454 g rate). Achillea at the 113.5 g rate only resulted in stunted plant growth while the 227 g and 454 g rates resulted in severe phytotoxcity and plant death.
Philip L. Carpenter
Broad-spectrum herbicides severly injured container-grown (Cotoneaster divaricata, Rehd. & Wils. and Euonymus fortunei, (Turcz.) Hand-Mazz. cv. Coloratus, because of rapid leaching into the root zone as a result of the porous peat-perlite medium. Injury was eliminated when activated carbon at 0.75 kg/m3 was mixed into the medium. Weed control was achieved by applying a 2.5 cm layer of the medium containing herbicide (but not activated carbon). The most effective herbicides were dichlobenil (0.44 g/m2), dichlobenil (0.44 g/m2) plus trifluralin (0.22 g/m2), or simazine (0.44 g/m2).