THE PEACH REPLANT PROBLEM IN ONTARIO: V. THE RELATION OF PARASITIC NEMATODES TO REGIONAL DIFFERENCES IN SEVERITY OF PEACH REPLANT FAILURE

Peach production in Ontario is largely restricted to the Niagara Peninsula and Essex County, areas that are separated by some 200 miles but have a similar climate. The peach replant problem has been much more serious in Essex County than in the Niagara Peninsula. A survey of mature peach orchards showed that Pratylenchus penetrans (Cobb, 1917) Sher & Allen, 1953, is considerably more prevalent in peach soils in Essex County than in the Niagara Peninsula. In both areas, orchards that had a previous history of the replant problem had three to four times greater soil population of P. penetrans than those with no such history. Soils of finer texture were shown to limit the populations of P. penetrans, and the relatively low numbers of this nematode in the Niagara Peninsula appear to result from the influence of the finer soils prevailing in that region. The effect of different soil-particle sizes on the build-up of P. penetrans may explain the distribution of the peach replant problem in Ontario.