Effect of taro leaf blight on leaf number.

Leaf blight (Phytophthora colocasiae Racib.) of taro (Colocasia esculenta (L.) Schott) causes a reduction in leaf number compared with healthy control plants. The proportional reduction in leaf number provides a partial disease index if the time when the disease becomes established in the crop is fixed. The reduction in leaf number, after equilibration, is directly proportional to the number of leaves on healthy plants, which varies over the crop cycle. This has implications for the design of disease management strategies involving intervention during the growing season.