Burndown and Early Season Weed Control – North

Posted 3/3/2015
A significant portion of yield is at risk if early emerging weeds are allowed to complete with crops during the first 4 weeks of planting.


  • A significant portion of yield is at risk if early-emerging weeds are allowed to compete with crops during the first 4 weeks after planting.
  • Burndown herbicide applications are an essential part of weed management in corn and soybean.
  • Environmental conditions affect herbicide performance, weed susceptibility to herbicides, and crop development.
  • Additional information on the importance of Burndown and Early Season Weed Control can be found in the Considerations for Burndown and Early Season Weed Management.

What is at Stake?

If left uncontrolled, weeds can cause reduced yield potential, crop quality loss, harvest difficulties, and cause future weed management issues due to weed seed production. The use of herbicides presents growers with an attractive return on investment as well. Annual herbicide sales in the U.S. are estimated at approximately $7 billion annually and return approximately $26 billion because of higher yield and better quality products.1

Weed Identification

Weeds emerging prior to or at planting are the most competitive with corn and soybean.2 The timing and intensity of weed emergence determines which species will be the most competitive with the crop. Knowledge of when weed species are likely to emerge is important in planning effective weed control programs. The relative emergence sequence of several common weeds is provided in Table 1 below.

Table 1. Relative emergence sequence of common weeds.

Source: Buhler, D. D., Hartzler, R.G., Forcella, F., and Gunsolus, J.L. 1997. Relative Emergence Sequence for Weeds of Corn and Soybeans. Pest Management Fact Sheet 9. Iowa State University.
Winter annuals Prior to planting Around planting After planting
Marestail Kochia Common ragweed Waterhemp spp.
Biennial thistles Russian thistle Wild buckwheat Black nightshade
Field pennycress Common lambsquarters Velvetleaf Large crabgrass
Shepherd’s purse Giant ragweed Foxtail spp. Wild proso millet
White cockle Smartweed spp. Pigweed spp. Fall panicum
Common sunflower Cocklebur Jerusalem artichoke
Hairy nightshade Field sandbur Marestail
Dandelion Canada thistle
Foxtail barley Yellow nutsedge

Treatment Recommendations

Fields should be scouted and weeds controlled throughout the season. The timing of a herbicide application should take into consideration the protection of yield potential, correct herbicide use rate for weed size, and environmental conditions.

Weed management tactics for tough-to-control weeds such as marestail, giant ragweed, kochia, lambsquarters, Amaranthus species, and others can be found in the Forum.

Minimize the Risk of Weed Resistance

  • Integrated weed management principles should be applied. Multiple sites-of-action with overlapping weed spectrums should be used in rotation, sequences, or mixtures.
  • The full recommended herbicide rate and proper application timing should be used for the hardest-to-control weed species in the field.
  • Fields should be scouted after herbicide application to ensure control has been achieved. Avoid allowing weeds to reproduce by seed or to proliferate vegetatively.
  • The field should be monitored and equipment cleaned between sites.

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