Yuma County, Arizona
June 17, 2002
Yuma County Office
Hay storage losses: Hay kept in storage loses weight due to a variety of factors. Hay exposed to the weather is most subject to losses, and storage in a barn or covering hay with a tarp can minimize these losses. Hay normally loses weight due to shrinkage or loss of moisture. Hay harvested at 20% moisture may reach a moisture content of less than 10% after 1 to 2 months. Hay also loses dry matter due to respiration even at low moisture contents. Respiration is a normal plant process where sugars are used for maintenance of plant structure and metabolism. Storage losses can range from less than 5% to more than 50% and can be accompanied by a decrease in forage quality.
Insect Management: Alfalfa caterpillar, Colias eurytheme,( picture, larvae) is a warm weather pest of alfalfa. There are seven generations per year in the low desert between May ad October. Check fields for alfalfa caterpillars when yellow alfalfa butterflies appear in May. Butterflies are seen flying over tall alfalfa most likely emerged from that field. Eggs are laid singly, standing on end, on the upper surface of leaves in fields with re-growth under 6 inches. Larvae hatch in 3 to 10 days, grow to about an inch long and pupate in approximately two weeks. Alfalfa caterpillars are green with white stripes down their sides and are distinguished from beet armyworm ( picture, larvae) by their velvety appearance. Monitor fields weekly from June through October, checking 2 to 3 times per week during periods of heavy infestations. Take 5 sweep counts in 4 to 5 field locations. Check worms for parasitism by pulling heads of an alfalfa caterpillar larva, squeeze out the body contents, and looking for an Apanteles wasp larva. Treat when field counts average 10 non-parasitized caterpillars per sweep.
Weed Control: Annual weeds that are present in fields that are fallow now but will be planted to alfalfa in the fall, can be controlled with repeated irrigations and tillage prior to planting. This is not true with perennial weeds such as bermudagrass and nutsedge. Tillage spreads perennial weeds, it does not control them! Bermudagrass and nutsedge can survive and emerge from several feet below the surface.
10 Year Summary (June 4, 1993 to June 17, 2002):
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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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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