Ryegrass Burndown

DR. LARRY STECKEL

 JACKSON, TENNESSEE

Ryegrass was a major issue last spring. For managing GR ryegrass, it is best to do it as early as practical and utilize a clethodim + glyphosate tankmix. This tankmix needs to be applied at least 30 days ahead of corn planting to use a clethodim rate that has any chance of controlling well established ryegrass.

Talking rates of clethodim can be confusing as there are 1 lb, 2 lb and 3 lb/gallon clethodim products available. Select Max is the clethodim trade name most are familiar with and it is a 1 lb/ gallon formulation. However, the most commonly used formulation is 2 lb/gallon. In using a 2 lb/gallon clethodim as an example, the best results from our research would be a 12 to 16 oz/A rate tankmixed with 32 oz/A of Roundup PowerMax.

 If corn planting is likely within 30 days of application, then two sequential shots of Gramoxone at 32 oz/A spaced about 10 days apart will typically do a reasonable job. Another fairly effective option is tankmixing Sharpen or Verdict with glyphosate and then apply Gramoxone about 10 days later.

An often-asked question is what about using clethodim for ryegrass within 30 days of corn planting? We have conducted research on this question and have found corn stunting can occur for a 16 oz/A rate used close to corn planting.

 However, there is a good bit of corn safety for lower rates of clethodim applied close to planting. As such, there is a supplemental label for Select Max applied 6 days before planting at a rate of 6 oz/A.  That low clethodim rate mixed with glyphosate can control newly emerged ryegrass but for well-established clumps of ryegrass that rate is inadequate.   ∆

DR. LARRY STECKEL: University of Tennessee