Lodging increases severity and impact of mycosphaerella blight on field pea

Abstract

Mycosphaerella blight, caused by Mycosphaerella pinodes, is a serious disease of pea (Pisum sativum) world-wide. The objective of this study was to assess the impact of lodging (reduced lodging treatment vs. control) and foliar fungicide (three to four applications of chlorothalonil vs. control) on the severity of mycosphaerella blight, and on seed yield and 1000-seed weight of 10 pea genotypes (three adapted cultivars and seven genotypes with partial resistance). In the reduced lodging treatment, a wire mesh was secured 30 cm above the ground; the crop was allowed to grow up through the mesh and be supported by it. The study was conducted under irrigation at two locations in Saskatchewan for 2 yr. Blight severity on stems, foliage, and pods was rated three to four times per year. The reduced-lodging treatment and application of fungicide reduced blight severity and increased seed yield and 1000-seed weight. The effects of reduced lodging and fungicide application were additive. Overall, lodging was associated with the largest reductions in seed yield and seed weight, but the impact of fungicide application was slightly larger than that of lodging for the three commercial cultivars. We conclude that losses caused by mycosphaerella blight may be reduced by breeding for improved resistance to lodging, but that application of foliar fungicide and breeding for partial resistance also hold promise. Key words: Pisum sativum, Mycosphaerella pinodes, resistance, fungicide, yield loss, quality