Yuma County, Arizona
December 29, 2003
Yuma County Office
Insect Management: Blue alfalfa aphid (picture) is a serious pest during the winter and spring months in the low desert. Blue alfalfa aphid is distinguished from pea aphid (picture) by uniformly dark antennae. Pea aphids have lighter antennae with dark bands at each joint (picture). The blue alfalfa aphid first appears in December or January when it may be more abundant than pea aphid. Both species are common throughout the spring, but pea aphid is more heat tolerant and may persist into early summer. In susceptible alfalfa varieties, blue alfalfa aphid may stunt grown and infested plants have smaller leaves, shorter internodes, leaf curling, yellowing, and leaf drop. Several species of predacious bugs and parasitic wasps attack these aphids. Sample alfalfa fields weekly when aphids appear, then every 2 to 3 days as numbers approach the treatment threshold of 40 to 50 blue alfalfa aphids per stem.
Weed Control: Freezing temperatures will cause crop injury but
is necessary to kill summer annual weeds such as sprangletop and sandbur.
Some summer annuals are selectively killed only by freezing temperatures.
10 Year Summary (Dec. 15 - Dec. 29, 1994-2003):
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.
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