Nematodes and fungal diseases in barley and wheat on Prince Edward Island

A total of 31 genera and 28 species of plant and soil nematodes were identified from 30 commercial fields each of barley and wheat on Prince Edward Island. Root-lesion nematodes, primarily Pratylenchus penetrans, were the dominant plant parasites, and the only endoparasitic nematodes recovered from roots. Root-lesion nematodes were the dominant genus in soil, but stunt nematodes (Tylenchorhynchus spp., primarily T. dubius, and Merlinius spp.), and pin nematodes (Paratylenchus spp.) were also recovered frequently. Common root rot, barley net blotch, and wheat leaf blotch, incited by Cochliobolus sativus, Pyrenophora teres, and Leptosphaeria nodorum, respectively, were prevalent in barley and wheat. The nematicide aldicarb reduced the numbers of root-lesion nematodes in roots and soil in experimental plots during 1984–1987, except from soil in wheat and barley in 1984 and in barley in 1986. Aldicarb treatments also increased grain yields significantly by 10% and 19% in 1984 and 1987, respectively. Aldicarb treatments did not affect the incidence of common root rot, barley net blotch, or wheat leaf blotch disease. Correlation and regression analyses of data from experimental plots did not indicate any significant relationships between population levels of root-lesion nematodes in roots or soil and severity of root or foliar diseases in barley or wheat.