Reducing Amaryllis leaf spot by spraying

Gill, D. L.

This disease (Stagonospora curtisii), is of concern to southern growers, because of characteristic spots on the leaves and also because the fungus attacks flower stalks and may cause them to topple before or during flowering or before the seed is mature. Many growers produce plants from seed, and these seedlings may remain in one bed for several years. Seedlings and other plants are commonly transplanted and sold in the South while blooming rather than when dormant. Because of this method of culture, bulb treatments are not feasible for control of this disease. Plants were sprayed with fungicides from the small leaf stage until blooming. Zineb, ferbam, captan, and Copper A all reduced infection. The first 2 gave greater reduction than the last 2. Sufficient sticker-spreader must be added to the spray to obtain coverage. The spray should be allowed to run down into the base of the bulbs since infection is frequent on the bulb scales. As an aid in control, old plant debris should be removed before growth starts in the spring. Rotation should be followed when practical. In areas which allow air circulation less disease should develop.