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Symptoms and Control Methods of Primula Leaf Spot Disease
Symptoms: It mainly affects the leaves of the plant. The disease spreads from the lower part of the plant to the upper part. The spots are usually 3 to 4 mm in diameter and brown; in severe cases, the diseased leaves wither and die, causing defoliation (see Figure 2). The disease is caused by Ramularia primulae. The pathogen overwinters as mycelium or conidiomata on diseased plant debris, and seeds can also carry the pathogen, becoming the primary infection source for the following year. The disease mainly spreads through conidia carried by air and rainwater. Reinfection is frequent during the growing season. Plants are usually prone to the disease in warm, humid weather and when nitrogen fertilizer is applied excessively.