Production Update:

Rhizoctonia: Rhizoctonia solani is usually of minor importance in Arizona, but the fungus can cause severe stand loss in some situations. Rhizoctonia is very versatile and can cause decay of the roots, stem, and leaves as well as the crowns. Symptoms usually occur during the warmer part of the growing season. Circular, concave, black lesions can appear on taproots but are not always seen in Arizona. Crown decay appears as dark, rotted areas within the crown tissue. The fungus can also girdle the stem near the soil line. The disease can cause circular lesions on the leaves. Control measures include resistant varieties, proper land leveling, and avoiding over-irrigation. No effective chemical control measures exist for rhizoctonia.

Insect Management: Alfalfa caterpillar, Colias eurytheme, ( picture) also known as alfalfa butterfly, is a warm weather pest of alfalfa (more information Alfalfa Caterpillar/Butterfly PDF file, 74 KB. There can be as many as seven generations between May and October, in the low desert. Start checking fields for alfalfa caterpillars when yellow alfalfa butterflies ( picture) first appear in May. When alfalfa butterflies are seen flying over tall alfalfa, they most likely emerged from that field. Eggs are laid singly ( picture), 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 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 off 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: Bermudagrass can be controlled with multiple applications of Select/Prism or Poast. The highest labeled rates of theses herbicides will slowly desiccate this weed over a 2 to 3 week period although regrowth will often occur a couple of weeks later. Two or three applications during the summer for two or three summers will bring this invasive perennial under control.

10 Year Summary (June 2, to June 13, 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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