Distribution of Plant-Parasitic Nematodes in Quebec Apple Orchards

Abstract

VRAIN, T. C., and G. L. ROUSSELLE. 1980. Distribution of plant-parasitic nematodes in Quebec apple orchards. Plant Disease 64:582-583. In a survey of apple orchards in southeastern Quebec in 1978, 351 soil samples were collected from 71 orchards in nine counties. Species in eight genera of plant-parasitic nematodes were found. Species of Pratylenchus, Paratylenchus, and Xiphinema were detected most frequently. Pratylenchuspenetrans or Pratylenchus crenatus were found in all 71 orchards, at densities greater than 33/100 cm 3 of soil in 58% of infested samples. Xiphinema americanum was found in 88% of the orchards. Quebec is a major apple-growing province of Canada, producing about 110,000 metric tons annually on 8,000 ha. Most orchards are 20- to 30-yr-old trees on standard rootstocks such as Malus robusta 5 or seedlings (12). High density plantings on size-controlling rootstocks are gradually replacing the old orchards. Apple trees with union necrosis and decline have been found in Quebec (13,14). A virus closely related to tobacco ringspot virus was isolated from affected trees, and Xiphinema americanum, a vector of this virus, was always present in the rhizosphere of those trees. Because of the potential for damage to new orchards by Pratylenchus penetrans (9) or by X. americanum, this survey was undertaken to determine their distribution and density in apple orchards of southern Quebec.