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D. Brault, K.A. Stewart, and S. Jenni

Optical properties of paper and plastic mulches were determined in experiments on mulched head lettuce (Lactuca sativa L.) grown in organic soil in 1997-98. Mulches used in 1997 were a coextruded white/black polyethylene, a beige paper coated with latex on both sides and a black paper coated with latex on both sides. Three supplementary mulches were added in the 1998 experiment: beige paper coated with a biodegradable polymer either coated on the underside, on the top side or on both sides. Optical properties of the polyethylene mulch remained stable over the course of the experiment. As the paper mulches aged, they changed structurally, spectrally, or both, but remained in place until harvest. The black paper was the only mulch that offered complete weed control, although the weeds under the other mulches did not develop beyond the cotyledonary or two-true-leaf stage.

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Jeffrey G. Norcini, Melvin P. Garber, William G. Hudson, Ronald. K. Jones, Ann. R. Chase, and Kane Bondari

Members of the American Association of Nurserymen and the Society of American Florists were surveyed as to their use of herbicides and nonchemical alternative weed control practices for 1993. Glyphosate was the top-ranking herbicide among the total of 37 reported, in terms of number of respondents and estimated total amounts of active ingredients applied. It was used by all but two of the respondents that used herbicides in their operations. Oryzalin was the top-ranked preemergent herbicide, and was second only to glyphosate in number of respondents and amount of active ingredient applied. The highest estimated use in amounts of active ingredient applied was in the southeastern (43% of total) and north-central (27% of total) regions, nearly two to three times the estimated use in the northeastern or western regions. However, there were only about 50% more respondents in the southeastern or north-central regions compared to the other regions. About 56% of herbicide active ingredients used were in field sites, 22% in container sites, 19% in perimeter areas, and 3% in green-houses. Large firms (annual sales more than $2,000,000) used the greatest estimated total amount of active ingredients, while small firms (annual sales more than or equal to $500,000) tended to use nonchemical alternatives the most. Nearly all respondents used handweeding or hoeing as part of their weed control program. Mowing was used by 84% of the respondents, 71% used tractor cultivation, and 66% used mulches (includes gravel and black plastic). Alternative methods were rated as somewhat effective to very effective by 65% or more of the respondents who used them.

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Michele M. Bigger*, Hannah M. Mathers, Jennifer A. Pope, and Luke T. Case

The objective of this study was to evaluate the extent and duration of efficacy and phytotoxicity of two new formulations of dichlobenil (Casoron 50WP and Casoron CS), applied alone or onto two bark mulches, pine nuggets or shredded hardwood. The herbicide treated bark was compared to a control (weedy check), direct sprays of the herbicides and mulch alone. Three granular preemergent herbicides, dichlobenil (Casoron 4G) and two formulation of flumioxazin (Broadstar 0.17G, VC1351, and VC1453) were also evaluated for a total of 12 treatments. The trial started on May 23, 2003. Visual ratings and dry weights were evaluated for efficacy at 4, 8 and 16 weeks after treatment (WAT) and phytotoxicity 2, 4, 8, and 16 WAT. Ratings of efficacy were based on a 1-10 scale where, 0 represents no control, 10 represents complete control. Visual rating scores of 1 (no injury) to 10 (complete kill) were used for phytotoxicity on Salvia May Night. The two most efficacious treatments are Casoron CS as a directed spray (7.9) and treated on pine nuggets (9.0). The hardwood bark with Casoron CS also was providing an efficacy rating of 7.75 in the analyses of combined dates 4 and 8 WAT. The weed control provided by the untreated hardwood bark and pine nuggets was not significantly different from the control. Four treatments—Casoron CS and 4G, Casoron CS on pine, and CS on hardwood—provided ratings of 3 and above for phytotoxicity, in the analyses of combined dates 2, 4, 8, and 16 WAT. Although the Casoron CS was the second most efficacious treatment it had a phytotoxicity rating of 9.25 over combined dates. The CS on pine, however, had a significantly reduced phytotoxicity rating (3.5) and superior efficacy.

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Amy O'Leary, Paul Henry, and She-Kong Chong

There has been recent speculation in trade journals that landscape fabrics, while doing an excellent job of weed control, may have a detrimental effect on ornamental plant growth. A study is in progress to investigate the manner in which hardwood mulch and applied landscape fabric affect soil temperature, soil aeration, and water content over 18 months. Two experiments are in progress, one with compost incorporated at 50% soil volume, the other with no compost incorporation. The experimental design is a randomized complete block with four treatments (mulch, fabric, fabric plus mulch, and control) and four plants per plot. Each plot has been planted with herbaceous perennials so as to allow analysis of treatment effects on plant growth. Soil temperature within plots is monitored on a continual basis. Soil aeration is measured every two weeks using installed oxygen tubes. Water content is measured using time domain reflectometry 24 and 48 h after a significant rainfall event. Preliminary results suggest that hardwood mulch and landscape fabric are similar in their effect on soil water content 0 to 48 h after a significant rainfall event. However, after 48 h, hardwood mulch increases soil water retention compared to landscape fabric.

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Richard L. Harkess and Robert E. Lyons

Combinations of seed rate, spacing and weed control treatments were evaluated for their effect on the performance of The Virginia Tech Transplanted Meadow technique. The treatments consisted of seed rates of 112 g or 56 g per 90 m-2; within-row transplant spacing of 30, 45, or 60 cm; and mulch, oryzalin, or nothing applied for weed control. Plant competition alone was insufficient for effective weed control whereas oryzalin was the best but also reduced the plant stand and floral display. Mulch provided effective weed control with maximum floral display. Close transplant spacing within rows resulted in quick site coverage but this advantage disappeared after 8 weeks when no difference in floral display was observed. Seeding rate did not affect site coverage until the meadow reached maturity at 12 weeks. The lower seed rate allow ed more lodging, resulting in a more open appearance and greater light transmission through the canopy. Chemical name used: 4-(dipropylamino)-3,5dlnitrohenzenesulfonamide (oryzalin).

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Joseph DeFrank, Tadashi Higaki, and Joanne Imamura

Yield components of 4 anthurium cultivars over a 2 year harvest period were determined. The varieties are `Ozaki' (red color-OZ), `Nitta' (orange-NT), `Kozohara' (dark red-KZ) and `Marian Seefurth' (pink-MS). The herbicide treatments are: diuron (1.1 kg ai/ha) every 3 months (DN); granular formulation of oxyfluorfen (2%) and oryzalin (1%) (3.4 kg ai/ha) in an alternating 3 month cycle with diuron (1.1 kg ai/ha) (OO). Black polypropylene mulch (PM) is the non-chemical control treatment. Yield components include: total cut flower yield, mean stem length and mean flower size (spathe width × length). Total flower yield was not significantly affected by weed control treatments. Yield ranking was: MS>KZ=NT>OZ. A significant interaction was recorded for stem length and flower size. OZ stem length was unaffected by weed control treatments while the others showed variations dependent on treatments. KZ and OZ flower size was not affected by weed control treatments, however, herbicide treatments did reduce flower size of MS and NT. Weed control ranking was: PM=00.>DI.

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Darren E. Robinson, Nader Soltani, Allan S. Hamill, and Peter H. Sikkema

Combining herbicides and fungicides can improve production efficiency; however, there is little information on the effect of these mixtures on weed control and processing tomato crop response. Six field trials were conducted from 2002 to 2004 in Ontario to study the effect of rimsulfuron and thifensulfuron applied alone or in combination with metribuzin and with or without chlorothalonil or copper fungicides on processing tomato. There was no visual injury or reduction in marketable yield of processing tomato with rimsulfuron or thifensulfuron alone or when tank-mixed with chlorothalonil or copper hydroxide. Rimsulfuron, thifensulfuron, rimsulfuron plus metribuzin, and thifensulfuron plus metribuzin could be tank-mixed with chlorothalonil without a reduction in weed control. However, efficacy of rimsulfuron and thifensulfuron were reduced when tank-mixed with copper hydroxide. The reduction in weed control incited by adding copper hydroxide was overcome with a low rate (150 g·ha–1 a.i.) of metribuzin for thifensulfuron but not rimsulfuron. Application of rimsulfuron and thifensulfuron alone or with low rates of metribuzin and chlorothalonil could provide tomato growers with a single-pass treatment for the control of troublesome weeds and diseases.

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Sujatha Sankula, Mark J. VanGessel, Walter E. Kee, and J.L. Glancey

Field studies were conducted in 1997 and 1998 to evaluate labeled (1×) or reduced (0.5×) rates of metolachlor plus imazethapyr preemergence either broadcast or band applications to lima bean (Phaseolus lunatus L.) planted in 30-inch (76-cm) or 15-inch (38-cm) rows for weed control, yield, harvestability, and harvest recovery. Lima bean was planted in large plots simulating a commercial production system. All 30-inch rows were cultivated once 40 days after planting in 1997 and 21 days after planting in 1998. No differences were noted in weed densities between treatments both years. Marketable lima bean yield was greater from plots thatwere spaced 15 inches apart in 1997 only. However, total hand-harvested yield in both years, machine-harvested yield in 1998, and marketable yield in 1998 were not different between treatments. Measurements on harvest recovery revealed that a greater number of unstripped pods were left on plants after harvest in 15-inch row plots that were sprayed broadcast with 1× herbicide rate in 1997 only. Weight of beans lost per unit area and trash weight from 7-oz (200-g) bean sample was similar among treatments both years. Overall, weed control, yield, and harvest efficacy of lima bean was not impacted by row spacing, herbicide rate, or method of herbicide application in a commercial production system.

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Jialin Yu, Nathan S. Boyd, and Zhengfei Guan

adequately control the weeds, and as a result, some seed production occurred which resulted in increased weeds present in the following strawberry crop. Despite the different weed spectrum between sites, the results consistently show that leaving the mulch in

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John Caldwell and Maurice Ogutu

Greater plant diversity is associated with reduced insect pest pressure, but field-scale vegetable production systems incorporating plant diversity have been lacking. Cucumber was grown in 1998 and 1999 at the Virginia Tech Kentland experimental farm, by direct seeding or transplanting into rye/vetch mixture rolled to make a no-till mulch alternating with strips of vetch left to flower as a habitat for beneficial insects between cucumber rows, or direct-seeded into black plastic mulch between habitat strips or with bare soil between rows. Rye and hairy vetch were seeded at 56 kg·ha–1 each the preceding fall; only rye was planted in plots without habitats. A rippled coulter, cutting shank, and daisy wheels mounted on a tractor-drawn toolbar enabled a belt-driven seeder to seed cucumbers without pulling the no-till mulch. One hand weeding in cucumber rows at 3 weeks after planting (WAP) provided weed control equivalent to pre-emergence herbicide. At 3 WAP, no-till transplanted cucumbers had higher above-ground plant dry weights than no-till direct seeded cucumbers in both years, but, at 6 WAP, cucumber above-ground plant dry weights were equal (1999) or higher (1998) in direct seeded no-till than in transplanted no-till or black plastic mulch on bare soil. In 1999, Pennsylvania leatherwings, Chauliognathus pennsylvanicus DeG. (Coleoptera: Cantharidae), a cucumber beetle predator, had higher densities and cucumber beetles lower densities in no-till plots than in black plastic mulch plots, and bacterial wilt incidence was reduced in plots with habitat strips and no insecticide application compared to plots without habitat strips and four insecticide applications. Cumulative marketable yields in no-till were 59% higher in 1998 and 23% higher in 1999 compared to yields on black plastic mulch.