Seeding Date, Carbofuran, and Resistance to Root‐Lesion Nematode Affect Alfalfa Stand Establishment

Abstract

The root‐lesion nematode, Pratylenchus penetrans (Cobb) Filipjev & Schuurmans Stekhoven, can reduce the establishment and productivity of alfalfa (Medicago sativa L.) in the northeastern and north‐central USA and in eastern Canada. Our objectives were to evaluate the effects of fallow and delayed seeding date, carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate) treatment, and plant resistance on P. penetrans populations in alfalfa roots and on alfalfa stand establishment and plant growth. In 1982,1983, and 1984, alfalfa genotypes varying in reaction to P. penetrans (‘Baker’, susceptible; ‘WL‐219’, low resistance; and MNGRN‐2 and MNGRN‐4, both with moderate resistance) were established in a Cowhorn sand (coarse‐loamy, mixed, nonacid frigid Aerie Haplaquept), naturally infested with high populations of P. penetrans. The alfalfa genotypes were seeded on different dates from 13 May to 14 July with and without soil applications of carbofuran at 2.2 kg a.i. ha−1. Plant stands were greatest and nematode populations were smallest when plots were seeded in late June or early July after 7 wk of fallow. Carbofuran application at seeding increased alfalfa stand establishment (21%) and reduced P. penetrans populations within alfalfa roots (37%) for ≈6 wk. Moderate resistance to P. penetrans in MNGRN‐4 increased alfalfa stand establishment (34%) and yield (22%) and reduced root‐lesion nematode populations within alfalfa roots (37%). Pratylenchus penetrans can be controlled in alfalfa during the establishment year by a combination of fallow and delayed seeding, use of carbofuran at establishment, and resistant cultivars.