The Stateus of Stem Nematodes in Arizona Alfalfa in 1985-86

Alfalfa stem nematodes have become a more serious pest since the advent of non -dormant alfalfa. Their distribution has increased and their period of feeding activity has been prolonged. A state survey has been conducted to determine the presence of the nematode in the principal alfalfa- growing areas of the state. The population dynamics were followed during the 1985-86 growing season. Alfalfa samples, including stems and crowns, were taken from selected fields in each geographic area and the nematodes were extracted. Populations from the samples determined the fields infested and the periods of feeding and reproduction. More than one -half of the fields sampled in the Salt River Valley were infested with the nematode and new infestations were found in Yuma County. Warm weather from October through the winter permitted nematode activity, causing serious stand decline. This pest is becoming more widely distributed and more economically important to alfalfa growers in Arizona