Alfalfa Stem Nematode (Ditylenchus dipsaci) in Wyoming. F. A. Gray, Associate Professor, Agricultural Economics Division, University of Wyoming, Laramie 82071. R. H. Boelter, Former Graduate Assistant, Plant Science Division, and G. P. Roehrkasse, Professor, Agricultural Economics Division, University of Wyoming, Laramie 82071. Plant Dis. 68:620-623. Accepted for publication 14 March 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-620.

The alfalfa stem nematode (Ditylenchus dipsaci) was found for the first time in Wyoming in 1980. Estimates of percent hectarage with D. dipsaci-infected plants in three areas of irrigated alfalfa surveyed in Wyoming were 2.5 ± 3.1, 21.8 ± 8.2, and 36.3 ± 9.8% for Goshen, Fremont, and Big Horn-Washakie counties, respectively. Plants infected with D. dipsaci were found in 63 of 121 fields surveyed. An average of 88.7% of fields with the stem nematode contained infected plants showing white-flagging symptoms. The stem nematode caused a reduction in dry forage yield and stem height in the alfalfa cultivar Ladak of 59.4 and 20.0%, respectively, in a greenhouse test.