Autumn Flower Anthracnose Control and Seedling Care Methods

Symptoms of anthracnose in autumn flowers: The disease mainly occurs on leaves, but can also attack petioles, tender branches, stems and stalks, and flower buds and petals. After leaves are infected, small round pale water-soaked spots appear at first, then gradually enlarge, turning grayish brown with brown margins, slightly raised. Finally the center of the lesion fades to grayish white to white; this diseased part is extremely thin, semi-transparent, and prone to perforation. In some cases the disease starts at the leaf tip and then spreads inward into the leaf blade. Lesions can often reach 1/3--1/2 of the entire leaf surface, and eventually the leaf dies. Some leaves keep dropping; severely affected plants often lose every single leaf. When petioles are infected, the diseased part turns brown and becomes slightly sunken, spreading toward the leaf blade to the midrib, veins and even the entire leaf, which turns brown; the lesion continues to spread downward, from the petiolule to the rachis, to the small branches, and even the stem and stalk, which turn brown and die. Under humid conditions, pale red sticky material, which is the acervulus produced by the pathogen, often appears on the lesions. Affected plants, in mild cases, have their normal growth and development impaired and lose their ornamental value; in severe cases, the whole plant dies. Flowers such as camellia (Camellia japonica), Chinese rose (Rosa chinensis), Aglaia odorata, white magnolia (Michelia alba), lily (Lilium), southern magnolia (Magnolia grandiflora), nandina (Nandina domestica), Japanese evergreen (Rohdea japonica), clivia (Clivia miniata), cactus (Cactaceae), plum blossom (Prunus mume) and orchid (Orchidaceae) are prone to this disease.

Control methods: Strengthen cultivation management, apply appropriate additional phosphorus and potassium fertilizer, avoid over-applying nitrogen fertilizer; watering should not be excessive and the potting soil should not be too wet; at the same time, improve ventilation and light transmission and reduce humidity. Diseased leaves and diseased petioles found should be pruned and burned immediately, and dead plants should be removed promptly. When the disease occurs, spray 50% thiram wettable powder at 500 times dilution or 70% thiophanate-methyl at 1000 times dilution, as well as 75% chlorothalonil at 800 times dilution, once every 10--15 days, for 2-3 consecutive sprays; alternating the chemicals can improve the control effect.