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

Production Update:
Alfalfa cutting: Alfalfa leaves can increase in weight by 30% during the day, and lose this weight during the night through respiration and transport to the root or growing points. Alfalfa leaves comprise about half the plant weight, so yield increases can theoretically be gained by harvesting in the evening. Yield increases may not be realized by cutting in the evening since respiration continues in cut alfalfa, but at least transport of sugars to the root will be stopped.

Insect Management: Beet armyworm (larva) is a common pest in low desert alfalfa from June through September. Egg masses, covered with white cottony scales, are deposited on the upper side of leaves. Eggs hatch in a few days and larvae reach full size in 2 to 3 weeks. Larvae pupate on or under the soil surface. Larvae appear smooth and are usually olive green, but color varies from bright green or purplish green. They have very fine dark stripes on their backs and pale yellow stripes on each side. First instar larvae web terminal leaves together and skeletonize the leaves, later dispersing through the crop. Spiders and predacious bugs prey on larvae and larvae may be parasitized on Hyposoter exigua (adult) wasps. Monitor fields weekly using a sweep net and check fields 2 to 3 times per week if heavy populations begin to develop. Make 5 sweep counts at each of 4 to 5 locations in the field. Treat when there are 15 non-parasitized beet armyworms of more than ½ inch per sweep.

Weed Control: All of the preplant herbicides registered for use in alfalfa can cause crop injury. These include Eptam and Balan. Trifluralin (Treflan) will reduce the new stand by 40 to 60% if put on prior to crop emergence. Prowl is not registered on alfalfa and will also hurt new seedlings if it is not incorporated.

10 Year Summary (Aug 12 - Aug 25, 1994-2003):

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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