Reproductive Efficiency of Pacific Northwest Populations of Meloidogyne chitwoodi on Alfalfa. J. N. Pinkerton, Research Associate, Nematology, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser 99350. H. Mojtahedi, and G. S. Santo. Associate Professor, and Associate Professor, Nematology, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser 99350. Plant Dis. 71:345-348. Accepted for publication 27 August 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0345.

Thirty-two geographic isolates of Meloidogyne chitwoodi were evaluated for their ability to reproduce on Thor alfalfa. Plant reactions to these populations ranged from nonhost to a suitable host based on egg mass index (EI) and reproduction factor (R). Thirteen populations that had EI >2 and R >1 were classified as the alfalfa race (race 2). M. chitwoodi race 2 was found in major potato production areas in the Pacific Northwest. Therefore, alfalfa rotation can no longer be generally recommended to reduce M. chitwoodi population densities.