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Weed Control and Regulation

Weed Control and Regulation. Eric Johnson Agriculture and Agri-Food Canada, Scott Research Farm. Sulfentrazone – PPO inhibitor / Group 14. 5-Aminolevulinate. Extraplastidic Oxidation. Chloroplast. Protoporphyrinogen IX. Protoporphyrin IX. Protoporphyrinogen IX. Light.

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Weed Control and Regulation

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  1. Weed Control and Regulation Eric Johnson Agriculture and Agri-Food Canada, Scott Research Farm

  2. Sulfentrazone – PPO inhibitor / Group 14 5-Aminolevulinate Extraplastidic Oxidation Chloroplast Protoporphyrinogen IX Protoporphyrin IX Protoporphyrinogen IX Light Protoporphyrinogen IX Oxidase PPO Inhibitor Stress Active Oxygen ACC Protoporphyrin IX Ethylene Senescence Mg-Protoporphyrin IX Protoheme Cell Membrane and Pigment Destruction, Tissue Decay, Plant Death Cytochromes Chlorophyll

  3. Outline • Authority herbicide • Authority (sulfentrazone) has received conditional registration in chickpea • Review of conditional registration • Review Sulfentrazone tolerance and efficacy in flax • Prospects for sulfentrazone registration in flax.

  4. Authority (Sulfentrazone) Registration • Conditional registration for two years until additional data is conducted and reviewed • Registration is for chickpea in Saskatchewan only • Additional efficacy and re-cropping data required from PMRA to grant full registration • Label is very restrictive.

  5. Authority Herbicide • Use parameters: • Apply prior to planting or up to 3 days after planting. • Application near or after crop emergence may cause severe injury. • DO NOT APPLY TO FIELDS PREVIOUSLY TREATED WITH AUTHORITY IN THE PAST THREE YEARS (36 MONTHS). • Performance parameters: • This product needs adequate moisture to activate.

  6. Authority herbicide • Weeds controlled: • Authority will only control germinating weeds. Weeds that are present at application may not be controlled. • Kochia • Lamb’s quarters • Redroot pigweed • Wild buckwheat

  7. Sulfentrazone Application Rates and Restrictions • Use on medium or fine textured soils only. NOT FOR USE ON COARSE (Sand, Loamy Sand) TEXTURED SOILS. • Do not use on soils with a pH of 7.8 or greater. • Do NOT apply to fine textured soils with less than 1.5% organic matter or any soil type with more than 6% organic matter.

  8. Authority – Re-cropping Label • For crops not listed in the table (ie lentils), a minimum rotational crop interval of 36 months must be observed.

  9. Continuing Research on Sulfentrazone • Efficacy – lowest effective dose • Re-cropping – underway at 4 locations in Prairies • Bioassay / sulfentrazone dissipation / impact of soil factors on sulfentrazone activity / sulfentrazone leaching – led by Schoenau, U of S

  10. Flax Tolerance to Sulfentrazone • Is dependent on soil cationic exchange capacity (texture, organic matter) and pH; • Cation exchange capacity more important than pH • More injury in soils with low CEC; low organic matter, coarse textured soils. • Moisture is also important. High rainfall after application will increase potential for injury.

  11. Tolerance of Flax to Sulfentrazone. Scott, 2004. a a a a a Injury rating – 2nd rating about 21 DAT Yield expressed as a Percent of Hand-weed check

  12. Tolerance of Flax to Sulfentrazone. Scott, 2005. a a ab b a Injury rating – 3rd rating near Crop Maturity Yield expressed as a Percent of Hand-weed check

  13. Tolerance of Flax to Sulfentrazone. Indian Head, 2005. a a a a a No visual injury at crop maturity Injury rating –2nd rating at July 15, 2005 Yield expressed as a Percent of Hand-weed check

  14. Sulfentrazone dose-response curves in ten soils as determined by shoot length inhibition of sugar beet Sand, Clay, OC %, pH 51, 31, 1.3, 7.8 k 19, 52, 1.3, 7.5 33, 39, 3.2, 5.6 23, 46, 2.3, 6.2 d 3, 83, 4.3, 7.2

  15. Sulfentrazone dose-response curves in ten soils as determined by shoot length inhibition of sugar beet Sand, Clay, OC %, pH 46, 38, 1.7, 7.7 k 14, 67, 3.0, 7.5 24, 51, 2.6, 6.3 d 60, 26, 2.4, 6.7 9, 72, 6.6, 6.1

  16. Relationship between I50 values for sulfentrazone and percent organic carbon in ten soils as determined by shoot length inhibition of sugar beet under laboratory conditions.

  17. Relationship between I50 values for sulfentrazone and percent clay content in ten soils as determined by shoot length inhibition of sugar beet under laboratory conditions.

  18. Conclusions – Soil Properties • The sugar beet shoot length bioassay is a suitable means of assessment for sulfentrazone in soil. • Bioassay is simple and quick and can be easily replicated. • Soil organic matter and clay content are important properties in reducing phytotoxicity from added sulfentrazone.

  19. Flax Tolerance Studies Funded by Sask. Flax • Tolerance studies conducted at Lethbridge, AB, Scott, SK, Melfort, SK, Saskatoon, SK (2 soil types), Indian Head, SK, and Brandon, MB in 2006 and 2007. • Rates evaluated ranged from 35 to 560 g ai/ha

  20. Tolerance Results • Lethbridge • sandy clay loam (36% sand, 30% silt, and 34% clay), 3.6% organic matter, pH: 7.8. • 2006: No injury observed; • 2007: highest rate (560 g ai/ha) resulted in unacceptable visual injury but did not affect plant stand or yield. • Scott • loam (38% sand, 41% silt, and 21% clay), 3.5% organic matter, pH: 6.5. • 2006 and 2007: Unacceptable injury at rates of 560 g ai/ha; reduced plant stand and yield;

  21. Tolerance • Saskatoon (Silty clay loam soil) • fine sandy loam (37% sand, 40% silt, and 23% clay), 1.9% organic matter, pH: 7.0 • 2006: Acceptable tolerance at all rates • 2007: Slight injury and plant stand reduction at highest rates. • Saskatoon (clay soil) • 12% sand, 28% silt, and 60% clay), 4.5% organic matter, pH: 7.2. • 2006: Some injury at highest rate, but no reduction in plant stand or yield • 2007: 280 and 560 g ai/ha resulted in just acceptable and unacceptable ratings at first rating date; however, crop recovered and no injury was evident at last rating date. Highest rate resulted in a reduced plant stand but yield was not affected.

  22. Tolerance • Melfort • Silty Clay loam (16% sand, 40% silt, and 44% clay), 11.3% organic matter, pH: 6.6. • 2006: Injury observed at highest rate; but no yield reduction • 2007: No injury. • Indian Head • Clay (16% sand, 20% silt, and 64% clay), 4% organic matter, pH 7.5. • 2006: no visual injury or reduction in plant stand • 2007: no visual injury; some reduction in plant stand at highest rate; no yield reduction. • Brandon • Clay loam (31% sand, 35% silt 34% clay ) 6.8% organic matter, pH 7.7 • 2007: Unacceptable crop injury at first rating date at rates of ≥ 140 g/ha but crop recovered and no injury recorded at 2nd and 3rd rating dates. No plant stand or yield reduction. • 2006: Unacceptable crop injury at highest rate early in the season; but crop recovered and no yield reduction.

  23. Weed Control Results Rate (g ai/ha) required to obtain 80% control of: • NP = not present • = site evaluated or weed present for only one year • (1) (2) = results in first year vs second year

  24. Weed Control Results – Additional Observations • Round leaved mallow • Present in Lethbridge in one year only • Not controlled at any rate • Shepherd’s purse • Present at 2 sites Scott (2006) and Elstow (2007) • At Scott 2006 - >80% control at rates of 140; at Elstow (2007): not controlled at any rate.

  25. Weed Control Results – Additional Observations • Wild mustard • Present at Kernen (2007). • Not controlled at any rate. • Russian thistle • Present at Goodale (2006) • Controlled at 70 g ai/ha.

  26. General conclusions from Flax Studies • A rate of 140 g ai/ha appears to be safe on soils tested, including a 2X rate margin of safety. • On most soils, rates of 140 g ai/ha or less were adequate to control redroot pigweed, wild buckwheat, and kochia. This is a rate that is safe to flax even at a 2 times that rate (overlaps). • On high organic matter soils, concern over lack of control of redroot pigweed.

  27. Effect of herbicide systems on control of wild mustard, kochia, and cleavers in flax. Scott 2008.

  28. Issues with Sulfentrazone registration • Re-cropping issues – PMRA wants more re-cropping information. • More efficacy data required; • Concerns over its solubility / potential to leach. • Won’t be any further registrations for sulfentrazone until PMRA is satisfied that data requirements are met.

  29. Lentil Injury from Sulfentrazone Residue - Scott Sulfentrazone injury in lentil

  30. Projects Underway / Future • Bioassay being used to measure dissipation and determine sulfentrazone ½-life in a number of prairie soils. • Bioassay being used to measure sulfentrazone movement in soil profile. • Some field work underway to ground-truth predictive ability of bioassay. • 2 years of re-cropping studies being conducted at a number of locations (including Scott). • More efficacy trials being conducted (including Scott). • Lentil – cultivar tolerance to sulfentrazone (CDC).

  31. ACKNOWLEDGEMENTS SASKFLAX PESTICIDE RISK REDUCTION PROGRAM SASKATCHEWAN PROVINCIAL MINOR USE PROGRAM

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