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Special Considerations For Control Of Annual Ryegrass And Legume Cover Crops

Annual ryegrass probably requires the most planning to ensure adequate control in a no-till system.

Here are some no-till recommendations slightly modified by Curran adapted from Plumer et al. 2013 and the Oregon Ryegrass Growers Seed Commission (http://ryegrasscovercrop.com/wp-content/uploads/2013/02/ryegrass-management-2013.pdf).

  • Glyphosate is the preferred herbicide for control of annual ryegrass. Paraquat (Gramoxone) does not provide consistent control. Glyphosate performance is reduced when day and night time temperatures are cool (30 to 50° F). Application during sunny warm days is best and cloudy weather will slow activity. Under cool conditions, it may take 2 to 3 weeks to kill the ryegrass and a second application may be necessary.

 

  • Apply glyphosate when day time high temperatures are at least 55 to 60° F. The ryegrass should be actively growing. Previous research suggests that small ryegrass is easier to control, but mild air temperatures 1 to 2 days before, during, and 1 to 2 days after application are likely more important.

 

  • Apply after the dew has dried and at least 4 hours prior to sunset. Do not tank-mix glyphosate with triazine herbicides (atrazine or metribuzin) or any other standard clay-based (DF, DG, WDG, F, etc.) residual herbicide. Remember that atrazine is a component of a number of soil-applied corn herbicides (Bicep, Cinch, Degree Xtra, Guardsman, Keystone, Lumax, Lexar, etc.). The corn herbicides Basis, Callisto, Resolve, Balance Flexx, or Corvus and the chloroacetamide products (Dual, Harness, Degree, Outlook, etc.) tank-mixed with glyphosate should not pose a problem.

 

  • Apply glyphosate at 1.25 to 1.5 lb ae/acre (48 to 64 fl. oz/acre for a 41% or 3 lb ae/gal glyphosate product). Include an appropriate nonionic surfactant at 0.25% v/v if not using a fully loaded formulation. Add spray grade AMS at 8 to 17 lb/100 gal or 2.5% (2.5 gal/100 gal) liquid AMS. Add AMS to the spray tank prior to adding glyphosate. Do not add other nitrogen fertilizers to the spray tank (e.g. 28 to 32% UAN). If the water source has a high pH (8 or greater), consider adding an acidifying agent (e.g. citric acid) to the spray solution to help increase glyphosate performance. Do not use water containing soil or organic particles that might inactivate glyphosate (e.g. pond water).

 

  • With glyphosate, reduce carrier water volume to 10 gal/acre if possible. Use flat fan nozzles rather than air induction type tips if possible. Never use flood type tips. Spray coverage is important for annual ryegrass control.

For control of clover or other legume cover crops:

  • Glyphosate alone will not kill most legumes, but it is useful in mixture with other herbicides. Gramoxone alone is also not very effective on legumes and should be mixed with atrazine or metribuzin for increased performance. Banvel/Clarity (dicamba) is one of the best herbicides for control of legume cover crops. It is often a necessary tank-mix partner with glyphosate for control of red or white clover. A 2,4-D ester formulation will effectively control hairy vetch, crimson clover, and field peas. Both 2,4-D ester and Banvel/Clarity can be tank-mixed with glyphosate without loss in activity and can be used in corn. Use a minimum of 12 fl. oz/acre of Banvel or Clarity or 2,4-D ester tank-mixed with glyphosate. Apply dicamba or 2,4-D ester 7 to 14 days before planting or 3 to 5 days after planting for greater crop safety and plant corn at least 1.5 inches deep. Clopyralid is also effective on legumes and is a component of several corn herbicides (Table 1). Banvel/Clarity and clopyralid are not suitable for soybean and 2,4-D ester (1 pt) must be applied at least 7 days ahead of soybean planting.

Source : psu.edu


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