Management of Pratylenchus penetrans Damage to Peppermint with Selected Nematicides. J. N. Pinkerton, Former Extension Nematologist, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331. H. J. Jensen, G. B. Newcomb, and R. E. Ingham. Emeritus Professor, Extension Nematologist, and Assistant Professor, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331. Plant Dis. 72:167-170. Accepted for publication 24 August 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0167.

Pratylenchus penetrans is the major nematode pest of peppermint in Oregon. Oxamyl, aldoxycarb, and carbofuran applied as broadcast sprays during spring reduced nematode densities and increased yields. Single treatments of 5.5 kg a.i./ha in early April were as effective as multiple treatments in April and May, or April, May, and June. Treatment effects were still evident after two seasons. Fall applications of oxamyl and carbofuran neither reduced overwintering nematode populations nor enhanced spring regrowth. Yield from a severely stunted stand on a sandy loam soil was increased by a 0.6-kg a.i./ha oxamyl treatment synchronized with root initiation in the spring, but 1.1- and 2.2-kg a.i./ha rates produced even greater yields than the lower rate. However, yields were not increased with these rates on a silty loam soil with similar pretreatment density of P. penetrans. P. penetrans management guidelines based on stand vigor, nematode population density, and edaphic factors are discussed.