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J.P. Morales-Payan and W.M. Stall

Field experiments were conducted in Santo Domingo, Dominican Republic, to determine the effect of increasing population densities of purple nutsedge (Cyperus rotundus) on the yield of eggplant (Solanum melongena). Purple nutsedge populations were established by transplanting viable tubers on 1-m-wide soil beds previously fumigated to suppress volunteer weeds. Nutsedge densities were 0, 50, 100, 150, and 200 plants (tubers) per m2. `Jira' eggplants and purple nutsedge were transplanted the same day and were allowed to interfere season-long. Purple nutsedge initial population densities of up to 100 plants per m2 did not significantly affect the fruit yield of `Jira' eggplants. However, nutsedge densities between 100 and 200 plants per m2 had a significant impact on eggplant yield, causing a linear decline in fruit yield as purple nutsedge density increased. Eggplant fruit yield loss was 22.3% at the density of 200 nutsedge plants per m2.

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J.P. Morales-Payan and W.M. Stall

Nursery experiments were conducted in Santo Domingo, Dominican Republic, to determine the effect of increasing population densities of purple nutsedge (Cyperus rotundus) on the growth of papaya (Carica papaya) transplants. Seeds of `Sunrise Solo', `Red Lady', and `Cartagena Ombligua' were separately sown in plastic 12 × 15-cm containers filled with a 1:1 mixture of sand and loamy soil. Viable purple nutsedge tubers were planted 5 cm apart from the papaya seeds. The purple nutsedge initial population densities were 0, 1, 2, 4, and 6 tubers per container. The crop and the weed were sown the same day and allowed to interfere during 6 weeks. Purple nutsedge density had a significant effect on the height, leaf area, and shoot dry weight of the three papaya cultivars. There was no significant difference in the response of the three papaya cultivars to purple nutsedge densities. In general, as purple nutsedge density increased, papaya growth decreased. Nutsedge interference caused papaya shoot dry weight losses of 15% at the density of one plant per container and 73% at six plants per container.

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Bielinski M. Santos and James P. Gilreath

Purple nutsedge can easily penetrate polyethylene mulch films. However, there are no reports on possible differences among mulch films. Because of this situation, field trials were conducted in Ruskin and Bradenton, Fla., during 2002 and 2003. In Spring 2002, the treatments were a) no mulch, b) black Pliant High Barrier mulch, and c) green Klerk's Virtually Impermeable Film (VIF). In Spring 2002, the films were a) black Pliant High Barrier, b) black IPM Bromostop, c) metallized Pliant, and d) green Klerk's VIF. The number of nutsedge emerged through the films was determined. No fumigants or herbicides were applied. Results indicated that the Klerk's VIF had the lowest nutsedge densities. No nutsedge control differences were found between the IPM Bromostop and the metallized Pliant films. These differences might be due to the physical properties of the films, including stretching and thickness.

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J.P. Morales-Payan, W.M. Stall, D.G. Shilling, J.A. Dusky and T.A. Bewick

Field trials were conducted in Gainesville, Fla., to determine the influence of nitrogen fertilization on the interference effect of purple or yellow nutsedge on the yield of fresh tomato. Nitrogen (N) rates of 50, 100, 150, 200, 250, 300, and 350 kg·ha–1 were applied broadcast to the soil. Before transplanting, 1-m-wide soil beds were covered with plastic and fumigated with methyl bromide to suppress the growth on undesired weeds. Nutsedge-free and purple or yellow nutsedge-infested tomato plots were separately established. `Solar Set' tomatoes were transplanted in the middle of the soil beds, 50 cm apart in a single row. In nutsedge-infested plots, weed densities known to cause significant yield reduction in tomato (100 purple nutsedge plants/m2 and 50 yellow nutsedge plants/m2) were uniformly established perforating the plastic and transplanting viable tubers in the perforations. Purple and yellow nutsedge tubers were transplanted the same day as tomatoes and were allowed to interfere during the whole crop season. Results indicate that N rates had a significant effect on tomato fruit yield in both nutsedge-free and nutsedge-infested treatments. The presence of either purple or yellow nutsedge significantly reduced the fruit yield of tomato at all N rates. As N rates increased, tomato fruit yield reduction caused by the interference of either nutsedge species also increased. When yellow nutsedge was allowed to interfere with tomato, fruit yield loss was as low as 18% at 50 kg N/ha and as high as 42% at 350 kg N/ha. In purple nutsedge-infested tomato, fruit yield reductions ranged from 10% at 50 kg N/ha to 27% at 350 kg N/ha. N effects on nutsedge-free and nutsedge-infested tomato yields were described by quadratic equations, with maximum tomato fruit yield values being reached between 200 and 250 kg N/ha in both nutsedge-free and nutsedge-infested treatments.

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Milton E. McGiffen Jr., David W. Cudney, Edmond J. Obguchiekwe, Aziz Baameur and Robert L. Kallenbach

Yellow and purple nutsedge are problem perennials that resist common control measures. High temperatures, irrigation, and relatively non-competitive crops combine to greatly increase the severity of nutsedge infestations in the Southwest. We compared the growth and susceptibility of purple and yellow nutsedge to chemical and cultural control measures at several locations in southern California. When not controlled, low initial populations of either species led to heavy infestations later in the season. Purple nutsedge was far more prolific in both tuber production and above-ground growth. Summer rotations that included crops with dense canopies severly decreased nutsedge shoot and tuber growth. Cool-season crops planted into heavy nutsedge infestations in the fall are generally unaffected because nutsedge infestations in the fall are generally unaffected because nutsedge soon enters dormancy and ceases growth. Solarization, or pasteurization of the upper soil layers, was effective in decreasing tuber formation. Tillage effectively spread local infestations over larger areas.

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James P. Gilreath and Bielinski M. Santos

runner plant nurseries with methyl bromide alternative fumigants HortScience 43 1495 1500 Gilreath, J.P. Santos, B.M. 2004 Manejo de Cyperus rotundus con alternativas al bromuro de metilo en tomate de mesa Manejo Integrado de Plagas y Agroecología 71 54

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Sanjeev K. Bangarwa, Jason K. Norsworthy and Edward E. Gbur

Use of wild radish ( Raphanus raphanistrum ) and rye cover crops for weed suppression in sweet corn Weed Sci. 56 588 595 Morales-Payan, J.P. Santos, B.M. Stall, W.M. Bewick, T.A. 1998 Interference of purple nutsedge ( Cyperus rotundus ) population

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Sanjeev K. Bangarwa, Jason K. Norsworthy, Edward E. Gbur and John D. Mattice

of Hawaii Honolulu, HI Morales-Payan, J.P. Santos, B.M. Bewick, T.A. 1996 Purple nutsedge ( Cyperus rotundus ) interference on lettuce under different nitrogen levels Proc. Southern Weed Sci. Soc. 49 201 (Abstr.). Morales-Payan, J.P. Santos, B

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

( Cyperus rotundus ) with polyethylene-mulched bell pepper ( Capsicum annuum ) Weed Technol. 17 543 549 Oliver, L.R. Buchanan, G.A. 1986 Weed competition and economic thresholds 71 91 Camper N.D. Research methods in weed science Southern Weed Sci. Soc

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Bielinski M. Santos and James P. Gilreath

( Cyperus rotundus ) in tomato and pepper Weed Technol. 18 141 145 Gilreath, J.P. Santos, B.M. 2004b Manejo del coquillo ( Cyperus rotundus ) con alternativas al bromuro de metilo en tomate de mesa Manejo Integrado de Plagas y Agroecología 71 54 58 Gilreath