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S. Gurusiddaiah and M. Ahmedullah

For the control of Reeds Canary grass (Phalaris arundinaceae) and yellow nutsedge (Cyperus esculentus) in blueberry fields, no satisfactory control measures are available. We tried microbially derived aerobic fermentation extracts of Pseudomonas syringae strain 3366 (P. S. 3366) as pre- and -post-emergence applications for the control of Reeds Canary grass and yellow nutsedge. In greenhouse studies using “conetainers,” 2 mg of extract per g of soil applied as preemergence completely inhibited seed germination and aerial growth of Canary grass, but had no effect on nutsedge. In addition, the same level of concentration of P. S. 3366 (2 mg of extract/g of soil) under field conditions also showed 99% inhibition of germination and growth of Canary grass, but had no effect on germination of nutsedge. However, 4-fold increase in concentration of P. S. 3366 extract completely inhibited the sprouting of yellow nutsedge in greenhouse studies. These studies indicate microbially derived extract of P.S. 3366 can be used and has potential for the control of these weeds. Post-emergence foliar sprays of P. S. 3366 extract in blueberry fields failed to inhibit the aerial growth of Reeds canary grass and yellow nutsedge.

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Brian Caldwell and Charles L. Mohler

Effects of several stale seedbed procedures on weed density and biomass were evaluated on a silt loam soil in central New York. After an initial rotary tillage, weeds were allowed to emerge and either single or multiple applications of glyphosate, propane flame, spring tine weeder, springtooth harrow, or rotary tiller were used to kill the weeds over a 4-week period. The last (or only) application occurred immediately prior to simulated seeding of a crop performed by passing an empty seeder through the plots. These stale seedbed treatments were compared with a control consisting of a single rotary tillage just before simulated planting. Flaming or glyphosate stale seedbed techniques significantly reduced density and biomass of the principal broadleaf species, common purslane (Portulaca oleracea L.) and common chickweed [Stellaria media (L.) Cyrillo], in most cases. A single delayed flame or glyphosate stale seedbed treatment was usually as effective as multiple treatments. None of the stale seedbed techniques was effective against yellow nutsedge (Cyperus esculentus L.). A flexible tine weeder was not effective as a stale seedbed weed-killing treatment in this study because of poor penetration of crusted soil. Penetration was better with a springtooth harrow, but this failed to reduce weed density. None of the stale seedbed treatments fully controlled weeds. However, glyphosate or flaming a stale seedbed could be incorporated into integrated weed management programs to improve control and reduce the need for herbicides. Broadleaf weed density within 3.8 cm of the center of the seeder wheel track was greater than elsewhere in the plot. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).

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Lisa W. DeVetter, Huan Zhang, Shuresh Ghimire, Sean Watkinson and Carol A. Miles

exploring plasticulture production using day-neutral cultivars targeting the fresh market. Black PE mulch is extensively used in plasticulture because of its low cost and ability to manage weeds, conserve soil moisture, modify soil temperatures, increase

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Susan L.F. Meyer, Inga A. Zasada, Shannon M. Rupprecht, Mark J. VanGessel, Cerruti R.R. Hooks, Matthew J. Morra and Kathryne L. Everts

field soil was then spread over the section. The black plastic was laid back in place and the edges sealed with duct tape. At the time of tomato planting, the 1-ft 2 section of black plastic was removed. Weeds were counted by species on 2 and 16 Aug

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Yushan Duan, Thomas W. Walters and Timothy W. Miller

plot (0% control = no weed injury from the herbicide treatment and 100% = no weeds present) as compared with nontreated plots (by definition 0% control) at about 2-week intervals during the raspberry growing season (May through September) for 3 years

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Nanik Setyowati and Leslie A. Weston

Dithiopyr (Dimension, Monsanto) is a turfgrass herbicide currently under evaluation for use in ornamentals. Granular herbicide depth and seed placement were evaluated in greenhouse studies with tolerant or susceptible weeds. Dithiopyr was applied preemergence to weeds at the rate of 2.24 kg/ha to Maury silt loam soil. Weed seeds were planted routinely at 0.64 cm depth. Dithiopyr placed at the soil surface or 0.64 cm in depth caused the greatest injury to seedlings, followed by dithiopyr at 1.28 cm depth. Dithiopyr at 2.54 and 3.81 cm below the surface had no effect upon seedling growth. When seeding depth was investigated, seed placed at 0.64, 1.28 or 1.91 cm below the surface showed greatest seedling injury when dithiopyr was routinely applied at 0.64 cm depth. Seed placement on the soil surface resulted in the least injury to weeds.

Peat moss was added to Maury silt loam soil and to sand to investigate the influence of organic matter upon activity. Soil with 2% peat resulted in the least injury to selected weed seedlings while sand, and sand plus up to 3% peat showed greatest injury. Sand amended with 5 and 6% peat also resulted in less injury to weed seedlings. Ivy leaf morningglory and KY 31 fescue were most tolerant of dithiopyr while barnyardgrass and large crabgrass were most sensitive. Dithiopyr uptake, translocation and metabolism studies will be conducted with susceptible and tolerant weed and woody ornamental species.

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Emily R. Vollmer, Nancy Creamer, Chris Reberg-Horton and Greg Hoyt

al., 1993 ). Cover crop mixtures suppressed weeds as effectively as a herbicide-controlled treatment for no-till tomatoes 4 weeks after transplanting ( Herrero et al., 2001 ). Creamer et al. (1996a) reported season-long weed suppression using cover

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Steven M. Borst, J. Scott McElroy and Greg K. Breeden

applied at 4.85 to 7.27 kg·ha −1 Cu during cool wet weather between October and March effectively controlled silvery-thread moss. In 2005, carfentrazone, a protoporphyrinogen oxidase inhibitor used for the control of a wide range of broadleaf weeds, was

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J.H. Connell, F. Colbert, W. Krueger, D. Cudney, R. Gast, T. Bettner and S. Dallman

A well maintained orchard floor is critical for insuring year-round orchard access and a clean almond harvest operation. This study compared three methods of orchard floor vegetation management over a 4-year period. The objective of this study was to evaluate cost effective vegetation management programs for difficult to control summer annual weeds while maintaining the population of desirable winter annual species. Common purslane (Portulaca oleracea) can be a major summer weed problem that interferes with almond harvesting operations. A low rate residual herbicide program controlled purslane more consistently than mechanical or chemical mowing programs. Desirable winter weed cover was preserved in all three management systems. The costs for each program were similar; however, there was a reduction in the number of operations required for both chemical mowing and low rate residual programs compared to the mechanical mowing program.

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Richard Smith*, Krishna Subbarao, Steve Koike, Steve Fennimore and Adelia Barber

Growers in the Salinas Valley are not able to rotate away from lettuce to other crops such as broccoli, as often as would be desirable due to economic pressures such as high land rents and lower economic returns for rotational crops. This aggravates problems with key soilborne diseases such as Sclerotinia minor, Lettuce Drop. Mustard cover crops (Brassica juncea and Sinapis alba) are short-season alternative rotational crops that are being examined in the Salinas Valley for the potential that they have to reduce soilborne disease and weeds. Mustard cover crops have been have been shown to suppress various soilborne diseases and there are also indications that they can provide limited control of some weed species. However, no studies have shown the impact of mustard cover crops under field conditions on S. minor. In 2003 we conducted preliminary studies on the incidence of S. minor and weeds following mustard cover crops in comparison with a bare control or an area cover cropped to Merced Rye (Secale cereale). There was a slight, but significant reduction of S. minor infection in one of three trials following mustard cover crops. Mustard cover crops also reduced emergence of Shepherd's Purse (Capsella bursa-pastoris) and Common Purslane (Portulaca oleracea) these studies. Mustard cover crops have distinct nitrogen cycling characteristics. They were shown to reach a peak of release of nitrogen in 30 to 50 days following incorporation into the soil. The levels of nitrogen that are released by mustard cover crops were substantial and could be useful in nitrogen fertilizer programs for subsequent vegetable crops.