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Corn

Weed Survey — Preplant

Start surveying and identifying weeds in the field where corn will be planted before harvesting the current crop. Also, look at weed records from the previous summer crop, as the major weed problems in corn will likely be summer weeds. Getting a realistic picture of the weed species present, their growth stage, and density is necessary for determining the best management methods. Identifying weeds early will ensure you select the most effective herbicides and cultural practices.

Weed surveys help you make decisions about weed management activities. Information collected over a period of years tells you how weed populations are changing and how effective your management operations have been.

Determine the dominant weed species present and maintain records, noting the severity of their infestations. Special weed problems are best controlled early before they compete with the corn when it is in the seedling stage; this is the most critical time in regard to yield reduction.

How to survey

  • Walk through each field in a random pattern.
  • Rate the degree of infestation for each weed species on your weed survey form. Indicate the growth stage of the weed (seedling or mature). Sketch a map of the field and mark areas with major weed infestations.
  • Use either a numeric scale from 1 to 5 (1 being the lightest, 5 being the heaviest), or rate the degree of infestation as "light," "medium," or "heavy."
  • Check fencerows, ditch banks, field edges, and wet spots as these may be problem areas for weed growth and, especially field edges, a potential source of wind-disseminated seeds. Also, check weed infestations in adjacent fields.
  • Sketch a map of the field and mark areas with major weed infestations for follow-up control action, noting carefully the location of weeds producing seed.
  • Pay particular attention to perennial weeds. Record the dominant species.

Recording weed survey results assists in weed management decisions including herbicide choice and cultivation practices. Information collected over a period of years tells how weed populations are changing and how effective management operations have been.

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