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Peter H. Sikkema University of Guelph

Weed Management in Corn Questions from Farmers. Peter H. Sikkema University of Guelph. Question # 1.

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Peter H. Sikkema University of Guelph

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  1. Weed Management in Corn Questions from Farmers Peter H. Sikkema University of Guelph

  2. Question # 1 I was planning to plant soybeans next spring so I applied Guardian for perennial broadleaf weed control last fall. I changed my mind and I would like to plant corn this spring. Will the corn be OK?

  3. Fall Application of Guardian Corn Injury the Following Spring Visible Corn Injury (%) Sikkema, UG

  4. Fall Application of Guardian Corn Injury the Following Spring

  5. Fall Application of Guardian Corn Yield the following Fall Corn Yield (bu/ac) Sikkema, UG

  6. Fall Application of Guardian Conclusions • The fall application of Guardian results in visible injury in corn the following spring • Purple discolouration • Stunting • In our studies there was a trend (9 bu/ac) to reduced yield, but it was not statistically significant

  7. Question # 2 Is weed control reduced if the herbicide is in spray solution in the sprayer for an extended period of time?

  8. Length of Time Herbicide is in Spray Solution Introduction • Sometimes a herbicide already is in spray solution but it cannot be spray immediately due to: • Mechanical breakdown • Sudden and unexpected rain • High winds

  9. Time in Solution Experiments • Herbicides were mixed and held in solution for: • 7 days • 3 days • 1 day • 0 days

  10. Time in Solution Herbicides Tested

  11. Time in Solution (PRE) Converge Sikkema, UG

  12. Converge – Sprayed Immediately

  13. Time in Solution (PRE) Yield (bu/ac) Sikkema, UG

  14. Time in Solution (PRE) Primextra + Callisto Sikkema, UG

  15. Primextra + Callisto – Sprayed Immediately

  16. Time in Solution (PRE) Summary • When herbicides were held in spray solution for an extended period of time there was: • No difference in pigweed control • A decrease in lamb’s-quarters control with Converge • A decrease in velvetleaf control with Converge and Frontier + Marksman

  17. Time in Solution (PRE) Summary • When herbicides were held in spray solution for an extended period of time there was (continued): • No decrease in corn yield with Frontier + Marksman, Primextra + Callisto and Battalion • A decrease in corn yield with Converge

  18. Time in Solution Herbicides Tested

  19. Time in Solution (POST) Distinct Sikkema, UG

  20. Time in Solution (POST) Roundup Sikkema, UG

  21. Liberty – Sprayed Immediately

  22. Time in Solution (POST) Yield (bu/ac) Sikkema, UG

  23. Time in Solution (POST) Summary • When herbicides were held in spray solution for an extended period of time there was: • No decrease in weed control with Distinct, Callisto + atrazine, Roundup or Liberty • No decrease in corn yield • It is recommended to spray the herbicide held in solution • Monitor field closely and re-spray if necessary

  24. Question # 3 Is there a benefit of adding Crop Booster to glyphosate in RR corn?

  25. No effect on weed control Crop Booster – 6 studies Sikkema, UG

  26. Crop Booster on RR Corn Roundup

  27. No effect on RR corn yield Crop Booster – 6 studies Sikkema, UG

  28. Crop Booster Summary • No difference in weed control • No difference in RR corn yield

  29. Question # 4 My corn is at the 8-10 leaf stage and I have weed escapes. Which herbicides are safest to apply at this late stage?

  30. Late Herbicide Application in Corn Corn Injury – 7 studies Sikkema, UG

  31. Late Herbicide Application in Corn Distinct Injury in Corn

  32. Late Herbicide Application in Corn Decrease in Corn Height – 7 studies Sikkema, UG

  33. Late Herbicide Application in Corn Corn Yield – 7 studies Sikkema, UG

  34. Late Herbicide Application in Corn Summary • Option results in greater injury than Accent • Distinct and Shotgun result in greater injury than Callisto + atrazine, Pardner and PeakPlus • There was no effect on corn yield in these studies

  35. Question # 5 I heard about glyphosate-resistant weeds. What are my weed management options in RR corn?

  36. Roundup Ready Corn Introduction • There are many approaches to weed management in Roundup Ready corn • Yield was maximized when Roundup was applied before weeds were 10 cm in height 1 • Profitability was maximized with one early postemergence application of Roundup 2 • BUT, the over-reliance on Roundup has resulted in the selection of glyphosate resistant weed biotypes or weeds naturally tolerant to glyphosate in other jurisdictions 1 Nelson, 2007 2 Thomas et al. 2007

  37. Roundup Ready Corn Weed Management Strategies • One application of Roundup applied early postemergence (EP) • One application of Roundup applied late postemergence (LP) • A tankmix of Roundup plus a residual herbicide (Marksman) applied EP • A sequential application of a preemergence (PRE) residual herbicide (Converge) followed by Roundup applied LP • A sequential application of Roundup applied EP and LP

  38. Roundup Ready Corn Velvetleaf Control – 8 WAA Weed Control (%) Sikkema, UG Nurse, AAFC

  39. Roundup Ready Corn Sikkema, UG Roundup + Marksman EP

  40. Roundup Ready Corn Pigweed Control – 8 WAA Weed Control (%) Sikkema, UG Nurse, AAFC

  41. Roundup Ready Corn Lamb’s-quarters Control – 8 WAA Weed Control (%) Sikkema, UG Nurse, AAFC

  42. Roundup Ready Corn Sikkema, UG Converge PRE; Roundup LP

  43. Roundup Ready Corn Green Foxtail Control – 8 WAA Weed Control (%) Sikkema, UG Nurse, AAFC

  44. Roundup Ready Corn Yield (bu/ac) Yield (T/ha) Sikkema, UG Nurse, AAFC

  45. Roundup LP Sikkema, UG Roundup LP Sikkema, UG

  46. Roundup Ready Corn Profit Margins Profit Margin ($/ac) Vyn, UG

  47. Roundup Ready Corn Conclusions • Weed management is field specific • The most consistent weed control was provided by the two-pass programs • Residual herbicide (PRE) fb glyphosate (LP) • A sequential application of glyphosate applied EP fb LP

  48. Roundup Ready Corn Comments • Due to the possibility of glyphosate-resistant weeds or weed shifts, the following are recommended: • A diverse crop rotation • Inclusion of multiple herbicide modes-of-action • Preemergence residual followed by glyphosate postemergence • Postemergence tankmix of glyphosate + another effective herbicide

  49. Question # 6 When is the best time to apply glyphosate in RR corn?

  50. Roundup Ready Corn Application Timing There is a temptation to delay the application until all the weeds have emerged

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