Sorghum Tips

Early Postemergence Herbicide Options for Grass Control in Grain Sorghum

This tip was provided by:

 

Ron Schnell, Cropping Systems – Statewide, College Station, ronschnell@tamu.edu

Statewide

Early Postemergence Herbicide Options for Grass Control in Grain Sorghum

Early competition from broadleaf and grass weeds in grain sorghum can result in yield loss. Use of burndown and soil active herbicides applied before planting or before sorghum emergence is critical for early season weed management. For extended weed control, especially grass control, additional soil active herbicides can be applied to control subsequent flushes of weeds. Other than for InzenTM herbicide tolerant sorghum, no products are labeled for broadcast application and control of emerged grasses in sorghum. Therefore, soil-active herbicides must be applied before subsequent flushes of grass weeds emerge for effective control. Many products limit postemergence applications based on the height of the crop. This generally aligns with growing point differentiation and is intended to reduce crop injury and maximize spray coverage to soil. There are many other options for postemergence control of broadleaf weeds in sorghum and many products can be tank mixed with soil active herbicides that are applied for extended grass control.

Below is a partial list of herbicide options and approximate cost at low and high labeled rates for postemergence applications. Prices are for planning purposes only. Actual cost may vary. Always read and follow label directions for specific rates and timing.

  1. atrazine – (AAtrex, Atrazine 4L) $5-10/A
    • Max of 4 pts/A, 5 pts/A if earlier application was used.
    • Apply before weeds exceed 1.5 inches in height and before sorghum exceeds 12 inches.
    • Lower rates (0.5-1.25 qts/A) for Pigweed control in other regions.
    • Supplemental Label can be found at: http://www.cdms.net/ldat/ld280000.pdf
    • Good control of broadleaves and some grasses.
    • Do not apply to coarse-textured soils or soil with less than 1% organic matter.
    • Be aware of rotation restrictions.
  2. dimethenamid-p – (Outlook, Establish) $11-23/A
    • 12-21 oz/A based on soil texture.
    • Apply before sorghum exceeds 12 inches.
    • Will not control emerged weeds.
    • Good control of grass and broadleaf weeds
  3. s-metolachlor – (Brawl, Medal, Dual II Magnum, Brawl II, Cinch, Medal II) $10-28/A
    • 1-1.67 pts/A based on soil texture.
    • Will not control emerged weeds.
    • Do not apply within 75 days of harvest.
    • Good control of several annual grasses.
  4. acetochlor – (Warrant) $13-27/A
    • 5-2.5 qt/A based on soil texture.
    • Apply before sorghum exceeds 11 inches (5-6 leaf stage).
    • Will not control emerged weeds.
    • Annual grass control and some broadleaves.
  5. pendimethalin – (Prowl H2O) $6.50-13/A
    • 5-3.0 pts/A based on soil texture.
    • Will not control established weeds.
    • Apply from 4-inch growth stage to layby.
    • Cultivate to cover the base of plants with at least 1 inch of soil.
    • Use drop nozzles if foliage prevents uniform soil coverage.
    • Use cultivation or irrigation to incorporate.
    • Excellent annual grass control.
  6. trifluralin – (Treflan) $3.50-9.40/A
    • 75-2.0 pts/A based on soil texture.
    • Will not control established weeds.
    • Postemergence incorporated, apply from 8 to 24-inch sorghum height.
    • Cultivate to remove emerged weeds and cover the base of plants with at least 1 inch of soil.
    • Use drop nozzles if foliage prevents uniform soil coverage.
    • Use cultivation to incorporate within 24 hr or apply through chemigation.
    • Excellent annual grass control.