Yuma County, Arizona
September 11, 2000
Yuma County Office
Alfalfa Seeding Rate: The optimum alfalfa seeding rate is difficult to define due to variations in seedbed conditions. Emergence of 50 seedlings per square foot is considered a good initial stand. Survival of half the emerged seedlings resulting in a stand of 25 seedlings per square foot during the first year should be adequate. A seeding rate of 20 pounds per acre is equivalent to approximately 100 seeds per square foot for raw seed and 67 seeds per square foot for coated seed. The rate of emergence and seedling survival may both average 50%, although the range may be from 20 to 70%. Plants are lost faster in higher compared to lower seeding rates, and stands after one year are often similar regardless of seeding rate.
Insect Management: Three-cornered alfalfa hoppers are found in alfalfa from spring into the fall. They feed by inserting their needle-like mouth parts into stems and sucking out juices. Adult female hoppers girdle stems by depositing eggs causing the stem and leaves to turn red, purple or yellow above the girdle. Adults are light-green, thick-bodied, triangular insects about one-fourth inch long which move about the plants and fly when disturbed. Nymphs are grayish-white, soft bodied, with saw-toothed spines on their backs and are confined to the lower portions of the plant. Nymphs may not be picked up in a sweep net. There are rarely enough three-cornered alfalfa hoppers in alfalfa fields to cause economic damage. An economic threshold has not been established, but if there are fewer than 15 three-cornered hoppers per sweep, it may not be economical to treat with insecticides.
Weed Control: May summer annual weeds become more difficult to
control this late in the season. They become less vegetative and produce
seed sooner. Once seed heads are formed, herbicides are generally not
well translocated and are often less effective.
10 Year Summary (August 28, to September 11, 1991-2000):
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director Cooperative Extension, College of Agriculture and Life Sciences, The University of Arizona.
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Information provided by:
Barry Tickes, firstname.lastname@example.org Extension Agent, Yuma County
Michael Ottman, email@example.com Agronomy Specialist
College of Agriculture, The University of Arizona.
Eric Natwick, firstname.lastname@example.org UCCE Imperial County - Farm Advisor
University of California, Davis, CA.
Material written September 11, 2000.
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