Effect of 3-year rotation sequences and pearl millet on population densities of Pratylenchus penetrans and subsequent potato yield

Various crops were evaluated in 3-year rotation sequences for their ability to reduce population densities of the potato root-lesion nematode, Pratylenchus penetrans, and improve subsequent potato (Solanum tuberosum) yield in field microplots. Forage and grain pearl millets (Pennisetum glaucum) were evaluated against oats (Avena sativa), Indian mustard (Brassica juncea), soybean (Glycine max), rye (Secale cereale), potato, and corn (Zea mays). Population densities of P. penetrans were high under rye, potato, oats, and Indian mustard and low under both forage and grain pearl millets. A single year of grain pearl millet after two consecutive years of potato or rye significantly reduced P. penetrans populations compared with 3 years of potato or rye and two consecutive years of corn, Indian mustard, oats, or soybean. One year of forage or grain pearl millet prior to potato decreased P. penetrans populations below the damage threshold of 1000 kg(-1) of soil. The subsequent potato crop produced the highest marketable and total yields following either three consecutive crops of forage or grain pearl millet or a single crop of forage or grain pearl millet preceded by rye or soybean. Total yields of potato 'Superior' were significantly negatively correlated with soil densities of P. penetrans in both fall 2002 (P < 0.001, r = -0.539) and spring 2003 (P < 0.001, r = -0.423). Both forage pearl millet 'CFPM 101' and the grain pearl millet hybrid 'CGPM H-1' have potential for the magagement of P. penetrans in Quebec's potato-production system.