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Yellow starthistleWeed Survey, Established Stands—Summer

Summer annual weeds, especially grasses, start to germinate in late February and early March and can continue to germinate through midsummer with irrigations.

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

Weed identification

The most dangerous summer annual is yellow starthistle. Identify common summer annual weeds and perennial weeds.

How to survey

Walk through each field in a random pattern, rating the degree of infestation for each weed species. 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.
  • Check areas around the field edges as these areas could be potential sources for wind-disseminated seeds.
  • Pay particular attention to perennial weeds; record the dominant species.
  • Sketch a map of the field and mark areas with major weed infestations.
  • Record results on an established stands weed survey form (134 KB, PDF).

The need for treatment depends on weed species, their competitiveness, the potential market for the alfalfa, and toxicity to livestock. In addition, vigor of the alfalfa stand is a complicating factor; weakened stands will require treatment when denser ones won't.

Important links

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

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