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Martin L. Kaps and Marilyn B. Odneal

Spring vs. fall plus spring (split) herbicide application times and single vs. tank-mix spring herbicide applications were compared as a means of extending summer annual weed control in vineyards. About 30% of the nontreated control areas were weed-covered by April or May of each of 3 years. Most treatments gave 60 or more days of acceptable annual weed control (≤ 30% cover) beyond the nontreated control. Fall plus spring application of diuron, norflurazon, or simazine at the half-label rate did not increase the days of control over spring application alone at the full-label rate. The tank-mixed herbicides diuron, norflurazon, and oryzalin in combinations of any two at the half-label rate were as effective as the full-label rate of these herbicides used alone. Weed control by oxyflurofen or simazine was extended by tank-mixing with oryzalin (half-label rates). Chemical names used: N -(3,4-dichlorophenyl) -N,N -dimethylurea (diuron); 4-chloro-5-(methylamino)-2-(a,a,a-trifluoro-m-tolyl)-3(2 H) -pyridazinone (norflurazon); 3,5-dinitro-N4,N4-dipropyl-sulfanilamide (oryzalin); 2-chloro-l-(3-ethoxy -4-nitrophenoxy)-4-(trifluoromethyl) benzene (oxyfluorfen); and 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine).

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Joseph DeFrank

Azolla (Azolla filiculoides) is a floating fern that maintains a symbiotic relationship with an N-fixing blue-green algae. In many parts of Asia, azolla is used as a green manure in flooded rice cultivation. Taro (Colocasia esculenta) grown under flooded conditions is used to produce a traditional Hawaiian staple, poi. Azolla has been present in Hawaii for many years, but is not used in a controlled way for either nutrient augmentation of production sites or weed suppression. In this experiment, azolla was removed from a stream on the island of Kauai and multiplied in a nursery pond. Phosphoric acid was added to the nursery pond as a nutrient (P = 5 ppm) at 5-day intervals to accelerate azolla growth. Azolla was moved from the nursery pond and added to taro production plots at a seeding rate of 488 kg·m–2. Phosphoric acid was used in production plots to hasten coverage of the water surface by azolla. Ten days after azolla inoculation, production plots were covered and taro seed pieces were planted. Weed dry weights from conventional and azolla covered plots were recorded 91 days after taro planting. Taro corms were harvested 315 days after planting. Weed dry weight in azolla plots was 86% less than conventional plots. Azolla delayed taro maturity, causing a 41% reduction in marketable corm yield.

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Sujatha Sankula, Mark J. VanGessel, Walter E. Kee Jr., C. Edward Beste and Kathryne L. Everts

Potential increases in the yield of agronomic crops through enhanced light interception have led many growers to consider using narrow rows in lima bean (Phaseolus lunatus L.). However, no information is available on how narrow row spacing affects weed management or fits into an integrated pest management strategy. To address this, field studies were conducted in Delaware and Maryland in 1996 and 1997 to evaluate the effects of row spacing (38 vs. 76 cm) on weed control, and on yield and quality of lima bean. Weed management inputs were also evaluated with labeled or reduced pre-emergence rates of metolachlor plus imazethapyr applied broadcast or banded. Only 76-cm rows were cultivated according to the standard practice for this production system. In general, row spacing, herbicide rate, and herbicide application method had no effect on lima bean biomass or yield, on weed density, control, or biomass production, or on economic return. However, weed control consistency was improved when wide rows were used, even with reduced herbicide rates, possibly because of cultivation. Using reduced herbicide rates and band applications resulted in 84% less herbicide applied without affecting weed control. Chemical names used: 3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide (bentazon); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl-4-(1-methylethyl)-5-oxo-1Himidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid (imazethapyr); 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide (metolachlor); 2-[1-(ethoxyimino)butyl]-5-[2-ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one (sethoxydim).

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R.E. Gough and R. Carlstrom

The herbicidal activity of wheat gluten meal (WGM) was evaluated on 17 species of monocotyledons and dicotyledons. Treatments included WGM at 0, 1, 2, 3, 4, 6, and 9 g·dm-2. Germination, shoot and root lengths, and root numbers were recorded. Treatments reduced germination and root extension in nearly all species. Leafy spurge (Euphorbia esula L.), redroot pigweed (Amaranthus retroflexus L.), shepherd's purse [Capsella bursa-pastoris (L.) Medik.], henbit (Lamium amplexicaule L.), quackgrass [Agropyron repens (L.) Beauv.], annual bluegrass (Poa annua L.), Canada thistle [Cirsium arvense (L.) Scop.], orchardgrass (Dactylis glomerata L.), purslane (Portulaca oleracea L.), annual ryegrass (Lolium multiflorum Lam.), and snap bean (Phaseolus vulgaris L.) were particularly sensitive. Germination of curly dock (Rumex crispus L.) and common lambsquarters (Chenopodium album L.) was suppressed at the higher rates. Germination of black medic (Medicago lupulina L.), spotted knapweed (Centaurea maculosa Lam.), mustard (Brassica sp.), and corn (Zea mays L.) were not substantially affected at any rate. Shoot growth of all species was inhibited at rates >2 g·dm-2, and at the highest rates no shoots developed. In nine species, shoot extension was stimulated at 1 g·dm-2 WGM. The herbicidal activity of WGM was not due to a “mulching” effect, since growth characteristics were also altered in bean seeds barely covered by the treatments.

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Barbara R. Bingaman and Nick E. Christians

Corn (Zea mays L.) gluten meal (CGM) was evaluated under greenhouse conditions for efficacy on 22 selected monocotyledonous and dicotyledonous weed species. Corn gluten meal was applied at 0, 324, 649, and 973 g·m–2 and as a soil-surface preemergence (PRE) and preplant-incorporated (PPI) weed control product. CGM reduced plant survival, shoot length, and root development of all tested species. Black nightshade (Solanum nigrum L.), common lambsquarters (Chenopodium album L.), creeping bentgrass (Agrostis palustris Huds.), curly dock (Rumex crispus L.), purslane (Portulaca oleracea L.), and redroot pigweed (Amaranthus retroflexus L.) were the most susceptible species. Plant survival and root development for these species were reduced by ≥75%, and shoot length was decreased by >50% when treated PRE and PPI with 324 g CGM/m2. Catchweed bedstraw (Galium aparine L.), dandelion (Taraxacum officinale Weber), giant foxtail (Setaria faberi Herrm.), and smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl] exhibited survival and shoot length reductions >50% and an 80% reduction in root development when treated with PPI CGM at 324 g·m–2. Barnyardgrass [Echinochloa crus-galli (L.) Beauv.] and velvetleaf (Abutilon theophrasti Medic.) were the least susceptible species showing survival reductions ≤31% when treated with 324 g CGM/m2.

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Kathie Kalmowitz, Ted Whitwell, Eldon Zehr and Joe Toler

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Krishna N. Reddy and Megh Singh

A field study was conducted to evaluate the effectiveness of Kinetic and Sylgard 309 organosilicone adjuvants to increase the efficacy of glyphosate for control of Florida pusley (Richardia scabr a L.), southern crabgrass [Digitaria ciliari s (Retz.) Koel], hairy beggarticks (Bidens pilos a L.), camphorweed [Heterotheca subaxillaris (Lam.) Britt. and Rusby], bahiagrass (Paspalum notatu m Fluegge), bermudagrass [Cynodon dactylo n (L.) Pers.], and torpedograss (Panicum repen s L.). Glyphosate, either at 0.5 or 1.0 kg a.i./ha, was applied alone or in combination with Kinetic, Sylgard 309, or X-77 using a tractor-mounted boom sprayer that delivered 187 liters·ha-1 at 207 kPa pressure. Glyphosate applied at 0.5 kg·ha-1 controlled > 94% of Florida pusley, southern crabgrass, hairy beggarticks, and camphorweed. Glyphosate efficacy improved on Florida pusley and southern crabgrass when applied with the adjuvants. Glyphosate, regardless of adjuvant, completely controlled hairy beggarticks and camphorweed. Control of bahiagrass, bermudagrass, and torpedograss with adjuvants was better than without adjuvants. However, glyphosate with Kinetic or Sylgard 309 was more effective in suppressing regrowth of these perennial grasses than glyphosate with X-77. Chemical names used: isopropylamine salt fo N -(phosphonomethyl)glycine with an in-can surfactant (glyphosate); proprietary blend of polyalkyleneoxide-modified polydimethylsiloxane and nonionic organosilicone adjuvant (Kinetic); silicone adjuvant mixture of 2-(3.hydroxypropyl)-heptamethyltrisiloxane, ethyloxylated, acetate EO glycol, -allyl, -acetate (Sylgard 309); mixture of alkylarylpolyoxyethylene glycols, free fatty acids, and isopropanol nonionic adjuvant (X-77).

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Diana L. Berchielli-Robertson, Charles H. Gilliam and Donna C. Fare

A 2-year study evaluated the effects of three weed species: eclipta [Eclipta alba (L.) Hasskarl], prostrate spurge (Euphorbia supina Raf.), and wood sorrel (Oxalis stricta L.) on growth of container-grown `Gumpo White Sport' azalea (Rhododendron eriocarpum), R. x `Fashion', and Berberis thunbergii DC. var. atropurpurea `Crimson Pigmy'. Competitiveness among weed species as ranked from greatest to least was eclipta, prostrate spurge, and wood sorrel. Greater populations of eclipta and prostrate spurge resulted in decreased shoot dry weight of `Fashion' and `Gumpo White Sport' azalea. Prostrate spurge had a similar effect on `Crimson Pigmy' barberry in both small (3.8-liter) and large (15.2-liter) containers, while eclipta reduced shoot dry weight of barberry only in large containers. Wood sorrel had little effect on shoot dry weight of `Fashion' and `Gumpo White Sport' azalea.

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Bielinski M. Santos, James P. Gilreath and Myriam N. Siham

Although methyl bromide (MBr) has been phased out in developed countries, limited amounts will still be available in the United States for the next few years through critical-use exemptions. Therefore, production practices reducing MBr use are desirable from the grower and environmental standpoints. Fumigation efficacy depends on the duration of fumigants in the soil and mulch permeability; thus, field trials were conducted to compare MBr retention of low- and high-density polyethylene (LDPE and HDPE respectively) mulches with seven metallized mulches and virtually impermeable films (VIF) from different manufacturers, and to assess the effect of MBr retention on nutsedge (Cyperus rotundus and C. esculentus) control with these mulches. The compared mulches were 1) white VIF; 2) black VIF; 3) white-on-black VIF; 4) cowound VIF, which has a clear nylon layer that covers the bed and is superimposed with a layer of black HDPE mulch; 5) metallized; 6) metallized heat trap with a black stripe on the bed center; 7) metallized with a black stripe on the bed center; 8) black LDPE mulch; and 9) black HDPE mulch. All treatments received 175 lb/acre of MBr + chloropicrin (Pic; 67:33 v/v). A nonfumigated control plot covered with LDPE mulch, and a treatment covered with HDPE mulch and fumigated with 350 lb/acre of MBr + Pic were also established. Nutsedge emergence through mulches increased rapidly beginning 18 days after treatment (DAT). Nutsedge populations at 28 DAT in the nonfumigated control covered with LDPE mulch had the greatest emergence (88.8 plants/ft2), followed by LDPE and HDPE mulches with 175 lb/acre of MBr + Pic (67.0 plants/ft2), HDPE mulch with 350 lb/acre of MBr + Pic (25.0 plants/ft2), and VIF and metallized mulches with 175 lb/acre of MBr + Pic (<2 plants/ft2). There were no significant differences in fumigant retention between the metallized mulches and VIF. These mulches retained 3.7 and 1.8 times more MBr than HDPE and LDPE mulches fumigated with 175 and 350 lb/acre of MBr + Pic, respectively.

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R.J. McGovern, F. Harper, C. Douglas and T.L. Thompson

Experiments at two commercial farms in Bermuda tested the effectiveness of solarization of narrow beds alone and together with metam sodium (MS) to enhance in-field production of broccoli (Brassica oleracea L. var. botrytis L.) and kale (B. oleracea L. var. acephala DC.) transplants. Soil treatments of clear, low-density polyethylene (LDPE) mulch (25 μm), white LDPE mulch (25 μm) plus MS (702 L·ha-1), and clear mulch plus MS were compared to bare soil. Mulches were applied and MS incorporated through rototiller cultivation 20 cm deep into 1.2-m-wide, flat seed-beds in the last week of June 1995. Mulches were maintained for 8 weeks. Either Broccoli `Pirate' or kale `Blue Curled Scotch' were seeded into transplant beds in Warwick and Devonshire parishes, respectively. Stand data was obtained for broccoli and kale 25 and 35 days, respectively, after seeding. Transplants were rated for root infection and biomass at 11 days (broccoli) or 31 days (kale) after seeding. In general, solarization was as effective as MS in suppression of soilborne pathogens of broccoli and kale plants. An additive effect on plant biomass was observed when solarization and MS were combined. All treatments significantly increased the establishment of broccoli plants and decreased root infection by Rhizoctonia solani in both crops. The incidence of Fusarium sp. was significantly decreased by all treatments in kale roots, and in broccoli by MS alone and in combination with solarization. Shoot fresh weight was significantly increased in kale by all treatments and in broccoli by solarization plus MS.