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

Production Update:

Frost management: 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: Pea aphid (picture), a pest of alfalfa during the spring months, can be distinguished from blue alfalfa aphid by lighter antennae with dark bands at each joint (picture). Blue alfalfa aphids (picture) have uniformly dark antennae. Pea aphids first appear in December or January but are usually less abundant than blue alfalfa aphid until later in the spring, but pea aphid may persist into early summer as they are more heat tolerant. They are found over most of the plant with heavy infestations and can deposit large quantities of honeydew which can foul harvesting equipment and supports the growth of sooty molds lowering hay quality. Regrowth may be stunted following cuttings with moderate to heavy aphid populations. Several species of predacious bugs and parasitic wasps attack these aphids. Sample alfalfa fields by taking 5 to 6 stem samples in at least 5 locations per field weekly when aphids appear, then every 2 to 3 days as numbers approach the treatment threshold of 40 to 50 aphids per stem for plants under 10 inches, 70 to 80 per stem for plants 10 to 20 inches tall and more than 100 aphids per stem for plants over 20 inches tall.

Weed Control: Raptor, the new broadleaf and grass herbicide developed by BASF, seems to work even slower than Pursuit. After one week, you may think it didn't get sprayed. After two weeks you probably will think it was sprayed but didn't work. The third and fourth week will bring some hope and it may be five to seven weeks before you're pleased with the control. Cold, slow growing periods are when it takes the longest. It is always a good idea to leave even a small area untreated for comparison.

10 Year Summary (Dec. 3 to Dec. 16, 1993 - 2002):

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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