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

Production Update:

Scald: Scald is damage that occurs to alfalfa associated with high temperatures and soil saturation. Scald is likely to occur when the soil is saturated for 30 hours or more and the temperature is greater than 100 degrees F. Damage can occur at lower temperatures following a long period of saturation. Injured plants become yellow and wilt within a week. Scald can be controlled by providing drainage, leveling fields, and avoiding standing water on ends of fields. Plants with foliage are much less susceptible to scald, so delaying irrigation until at least 4 inches of growth appears is probably the most effective control.

Insect Management: Webworms (picture) (alfalfa webworm, beet webworm and garden webworm) are occasional pests of desert alfalfa. The small webworm moths lay scale-like eggs on the undersides of alfalfa leaves. Larvae may grow to an inch in length, are yellowish green, with stripes or spots, depending on the species. Webworm larvae devour leaves beneath silken webs on the upper parts of alfalfa plants during the summer and fall. They do not usually cause serious economic damage. Harvesting usually greatly reduces the population levels infesting the alfalfa during the next crop cycle.

Weed Control: When alfalfa is taken out to establish a different crop, herbicides used during the previous year or two can cause problems to some crops. The herbicides used in alfalfa that have the longest persistence in the soil are Pursuit and Zorial. Those with moderate soil persistence are Sencor, Raptor, Balan, Eptam, Trifluralin and Kerb. Those with slight persistence are Gramoxone, Buctril and 2,4-DB. Poast and Select are not likely to cause problems.

10 Year Summary (July 15 - July 28, 1994-2003):

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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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