Yuma County Office
2200 W. 28^th Street, Ste. 102
Yuma, AZ 85364
(928) 726-3904
(928) 726-8472 FAX

Production Update:
Frost Damage: Frost-damaged alfalfa has lower quality due to leaf loss, lower digestibility, and decreased mineral content. Frost-damaged alfalfa may also accumulate toxic levels of nitrates in rare cases. Water application during freezing temperatures can raise the temperature, but waterlogging can produce negative effects. In the case of alfalfa, the best protection against frost is a healthy crop. Severe frosts can kill the tops of the alfalfa plant and new growth must occur from the base of the plant. Cutting alfalfa after a frost can stimulate this new growth near the base of the plant, but the new growth is then susceptible to subsequent frosts.

Insect Management: Cowpea aphid (picture) is a serious pest of alfalfa that can warrant treatment with an insecticide when populations are growing rapidly. Cowpea aphid is attacked by several predators (bigeyed bugs, damsel bugs, lacewings, lady beetles, and syrphid fly larvae) and parasites. Aphid parasites, Lysiphlebus sp.(picture) and Diaraetiella sp. (picture) have been reared from cowpea aphid mummies collected from both the high and low desert. Populations of sevenspotted lady beetle, Coccinella septempunctata (picture) and aphid parasites often build to levels capable of controlling cowpea aphid in alfalfa fields not sprayed with insecticides.

Weed Control: Trifluralin (Treflan) binds strongly to the soil and will last for 3-6 months on well drained soil. February is not too early to apply it for control of summer weeds. Eptam, on the other hand, moves readily with water and does not last long followed by multiple irrigations. February may be too early to apply it for summer weed control.

10 Year Summary (Jan 13 - Jan 26, 1995-2004):

Full Disclaimers

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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