Plant age and timing of epidemic initiation affect mycosphaerella blight in field pea

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Mycosphaerella blight (Mycosphaerella pinodes) occurs throughout western Canada and can severely reduce seed yield and quality of field pea (Pisum sativum). Field experiments were conducted to assess the impact of seeding date and timing of epidemic initiation on the severity of mycosphaerella blight on field pea. Early seeding or early initiation of the epidemic (early July) resulted in the highest severity and area under disease progress curve of mycosphaerella blight at the end of the growing season. Plants seeded later in the growing season showed less severe symptoms of mycosphaerella blight compared to those seeded earlier, and the blight severity was declined by delaying 1–2 weeks of disease initiation. However, late seeding reduces yield potential offsetting the benefit of disease reduction. A greenhouse study on the effect of both plant and tissue age on susceptibility to mycosphaerella blight revealed that both whole plants and leaf tissues became more susceptible as they aged. We conclude that delay of epidemic initiation in late June to early July through the use of foliar fungicides is effective in reducing mycosphaerella blight severity on the Canadian prairies.