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

Production Update:

Phytophthora Root Rot: Phytophthora Root Rot caused by the fungus Phytophthora megasperma was a major contributor to stand decline in Arizona before 1980. The importance of this disease has been lessened by the introduction of resistant varieties and by elimination of waterlogging. Phytophthora root rot is a cool season disease induced by wet conditions. A rotted taproot is characteristic of this disease, although leaves turn yellow and drop and lesions also appear on the roots. Infected fields can be saved by providing soil drainage. Lateral roots developing above the infected area can replace the function of the decayed tap root.

Insect Management: Spotted alfalfa aphid (SAA) (picture) caused severe damage to alfalfa in Arizona and California in the 1950s. Control was achieved through a combination of introduced parasites and host plant resistance. SAA still occasionally causes problems, but generally only when susceptible cultivars are grown. Since 1996, SAA has occasionally appeared in damaging numbers in highly resistant alfalfa varieties. A number of seedling alfalfa fields needed to be treated for SAA during the fall of 2002. The reasons for the appearance of this aphid in highly resistant cultivars is being investigated. There is every reason to believe that the highly resistant cultivars will continue to keep the SAA in check along with the indigenous and introduced natural enemies. SAA develops better under warm temperatures than pea aphid or blue alfalfa aphid.

Weed Control: Common groundsel (picture) is a weed in the composite family that has appeared in La Paz County and is becoming increasingly widespread. It has not been reported in Yuma County. It is a difficult-to-control weed that can be poisonous to cattle and horses.

10 Year Summary (Nov 18 - Dec 1, 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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