Yuma County, Arizona
May 20, 2002
Yuma County Office
Production Update:Alfalfa sensitivity to water stress: Alfalfa is most sensitive to water stress after a cutting. Yield losses as much as 30% have been reported for delaying irrigation after cutting by 6 days. It is impossible, of course, to irrigate immediately after cutting when producing alfalfa hay. However, the irrigation before cutting could be timed so that soil moisture is available for regrowth after cutting. Caution must be exercised to avoid soil conditions that are so wet at cutting that compaction results, which has long term consequences perhaps more serious than soil that is too dry at cutting.
Insect Management: Spider mites (picture, 71KB) are not common in alfalfa grown for hay and serious damage is often associated with water stress. When infested fields are watered, the problem often clears up in a matter of days. In recent years, spider mites have been more common in alfalfa hay fields during the spring/summer months. Spider mites infestations are usually confined to the lower leaves. They feed by inserting long needle-like mouth parts into leaves removing plant sap. Leaves become stippled with chlorotic spots. Infested leaves are covered with webbing and turn yellow. With severe feeding, leaves turn brown from necrosis and desiccation causing defoliation. Damage starts in the lower plant canopy moving upward. Feeding damage can reduce yield, quality and retard growth. Definitive monitoring and treatment guidelines have not been developed for spider mites in alfalfa grown for hay.
Weed Control: The time has passed when the contact herbicides,
Gramoxone and Buctril, can be safely and effectively used in alfalfa.
Hot, dry conditions, rapid crop regrowth, and preharvest intervals make
it difficult to safely and effectively use these products between March
and October. They also are weak on grasses, which are the predominate
10 Year Summary (May 7 - May 20, 1993-2002):
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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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