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Alfalfa
> Year-Round IPM Program > Winter > Weed
Survey
Alfalfa
 Weed
Survey, Established Stands—Winter
Survey for weeds in December through January
on a field-by-field basis. Be sure to check adjacent fields as
they may have very different weed populations
due to cropping history or soil type. In the Central Valley most
winter annuals start germinating in late September or October
and continue to germinate until late
January whenever soil moisture and temperature conditions permit.
Weed surveys help in making decisions about weed management
activities, 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
Identify common winter
annual weeds and perennial
weeds. The most dangerous winter annuals to livestock
are fiddlenecks and common groundsel.
How to survey
Walk through each field in a random pattern,
rating the degree of infestation for each weed species on your
weed survey form. Use either a numeric scale of 1 to 5 (1
being the lightest, 5 being the heaviest), or rate weed species
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 field edges
as these areas could be a potential source for wind-disseminated
seeds.
- Pay particular attention to perennial weeds.
- Sketch a map of the
field and mark areas with major weed infestations.
- Indicate the growth stage of the weed (seedling or mature).
- Record results
on an established
stands weed
survey form .
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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