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Duration of yellow nutsedge competitiveness after treatment with various herbicides

Duration of yellow nutsedge competitiveness after treatment with various herbicides. J. A. Ferrell*, H. J. Earl, W. K. Vencill University of Georgia. CYPER Competition. C4 perennial that reproduces vegetatively Higher photosynthetic rate than most crop species.

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Duration of yellow nutsedge competitiveness after treatment with various herbicides

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  1. Duration of yellow nutsedge competitiveness after treatment with various herbicides J. A. Ferrell*, H. J. Earl, W. K. Vencill University of Georgia

  2. CYPER Competition • C4 perennial that reproduces vegetatively • Higher photosynthetic rate than most crop species. • Yield reductions between 59 and 87% for corn, rice, and soybeans. • Alternate host for pathogens.

  3. Objectives • Determine time required for glyphosate, bentazon, imazapic and halosulfuron to render SORHA physiologically noncompetitive

  4. Physiologically non-competitive • 50% reduction in net carbon assimilation (AN) • Biomass accumulation most common parameter to describe competitiveness • Biomass accumulation directly linked with AN • 50% reduction in AN was a comparative indicator of competitiveness

  5. Materials and Methods • CYPER grown in greenhouse for 20 wk • Herbicide Treatments • Glyphosate 840 g ai ha-1 • Halosulfuron 140 g ai ha-1 + NIS • Imazapic 70 g ai ha-1+ NIS • MSMA 2200 g ai ha-1+ NIS • Bentazon 840 g ai ha-1+ COC • Plants treated at ~25 cm

  6. CYPER plants before treatment

  7. Materials and Methods • Photosynthesis and Stomatal Cond. • Li-Cor 6400 • PPFD = 1200 µmol m-2 s-1 • CO2 concentration (sample side) = 360 µmol mol-1

  8. Materials and Methods • Experiment conducted twice • Randomized Complete Block Design with 5 replications • All data normalized to the control • The data were pooled across runs

  9. Effect of Herbicide on AN Error bars = LSD(0.05)

  10. Effect of Herbicide on AN Error bars = LSD(0.05)

  11. AN50 Values

  12. Regrowth Biomass

  13. Bentazon recovery • Label suggests bentazon should be applied sequentially (7-10d) for CYPER control. • Pattern of AN decline and recovery 5 DAT has been observed in rice. • Recovery was attributed to metabolism • 85% metabolism observed 4 DAT

  14. Effect of Herbicide on gs Error bars = LSD(0.05)

  15. MSMA and gs • MSMA possibly inhibits the malic enzyme in C4 plants (Knowles and Benson 1983). • Accumulation of malic acid may lead to photooxidative damage (Devine et al. 1993). Hypothesis • Cellular leakage, leading to guard cell dysfunction, resulted in unregulated water losses via stomata. • Compromised cuticular integrity caused water loss from epidermal cells.

  16. Conclusions • Halosulfuron and imazapic renders CYPES physiologically non-competitive more quickly than glyphosate, MSMA, or bentazon. • A single application of bentazon did not control CYPES • gs highly correlated with AN, except for MSMA

  17. Any Questions?

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