Production Update:

Rain damaged Hay: Alfalfa must be dried or cured for safe storage as hay. Field and harvesting losses of hay are normally as high as 20 to 30%. Rain can increase these yield losses and reduce quality. Rain extends curing time and yield and quality are decreased due to loss of leaves, plant respiration, and leaching of nutrients. In a Utah study, artificial rain of 0.8 inches resulted in losses of yield (10%), available carbohydrate (19%), crude protein (10%), soluble minerals (14%), and total lipids (20%). Carotene, the precursor for Vitamin A, is sensitive to prolonged field exposure. Vitamin A is the most common vitamin deficiency in beef cows and horses.

Insect Management: Spider mites in alfalfa may be associated with water stress and infestations may clear up a few days after an irrigation. Infestations start in the lower plant canopy moving upward and leaves are covered with webbing. Spider mites insert needle-like mouth parts into leaves removing plant sap, causing a yellow stippling on leaves (picture). With severe feeding leaves turn brown, become dry, and drop from the plant. Feeding damage reduces yield, quality and retards regrowth. Spider Mite Species in Western Arizona and Southern California include: carmine spider mite (T. cinnabarinus Boisdival) (picture); desert spider mite (T. desortorum Banks); strawberry mite (T. turkestani Ugarov & Nikolski) (picture), and twospotted spider mite (Tetranychusurticae Koch) (picture). Pyrethroid insecticides can flare spider mite infestations. Sulfur may be used to suppress the populations.

Weed Control: Field and southern sandbur (picture) are controlled by preemergent applications of Triflurilan and Eptam unless it has survived the winter. Very early (1-2 leaf) postemergence application of Poast and Select/Prism will control seedling sandbur. This weed cannot be controlled selectively in alfalfa if it has overwintered or become well established.

10 Year Summary (March 23, to April 5, 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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