In the Central Valley most winter annual weeds start to germinate in late September or October and continue to germinate until late January, whenever soil moisture and temperature conditions permit. When the alfalfa crop germinates, survey the field for newly emerged weeds.
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.
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."
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.
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