1. Anonymous. 1971. United States standards for grades of potatoes (35 F.R. 18257). Consumer and Marketing Service, Washington, D.C. 19 pp.
2. Bishop, G.W., H.W. Homan, L.E. Sandvol and R.L. Stoltz. 1982. Management of potato insects in the western states. A western regional extension publication no. 64. 31 pp.
3. Brown, M.J., R.M. Riedel and E.C. Rowe. 1980. Species ofPratylenchus associated withSolanum tuberosum cv. “Superior” in Ohio. J Nematol 12:189–192.
4. Butterfield, E.J. and J.E. DeVay. 1977. Reassessment of soil assays forVerticillium dahliae. Phytopathology 67:1073–1078.
5. Cobb, N.A. 1918. Estimating the nematode population of soil. USDA Agricultural Technical Circular No. 1.