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Seedling of prickly lettuceLettuce

Survey for Weeds—Preplant

Start surveying your fields for weeds before harvesting the preceding crop. Determine the dominant weed species present, and maintain records of weed species and the severity of their infestations. Also, check weed infestations in adjacent fields.

Depending on when you monitor, you may see winter annual seedlings, summer annual seedlings, or perennial weeds. Weed surveys can help you select herbicides, rotational crops, and cultural practices.

How to survey your field

  • Walk through each field in a random pattern.
  • Rate the degree of infestation for each weed species on your weed survey form. Use either a numeric scale from 1 to 5 (1 being the lightest, 5 being the heaviest), or rate as "light," "medium," or "heavy."
  • Check fencerows, ditch banks, field edges, and wet spots as these may be problem areas for weed growth and potential sources for wind disseminated seed. Note the dominant species on the monitoring form.
  • Pay particular attention to perennial weeds.
  • 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.
  • Indicate the growth stage of the weed (seedling or mature).
  • Record results on a weed survey form.

Survey information collected over a period of years tells you how weed populations may change and how effective your management operations have been over the long term. By knowing which species are present, you will be able to make appropriate decisions on cultural and chemical controls.

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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