A Detailed Guide to Common Geranium Diseases and Their Control Methods

The main diseases of geraniums include:

① Leaf spot disease. In the early stage, needle-tip-sized, round or irregular small brown spots appear on the leaves, which gradually expand into dark brown or reddish-brown lesions. In severe cases, the entire leaf is covered with lesions until it dries up and falls off; the stems and branches also turn black, shrink and rot, and even the leaves on the stems wither and die, leaving only a few leaves at the top. Preventive measures: a. When cultivating in a greenhouse, do not plant too densely, and pay attention to frequent ventilation and light exposure; b. When watering, avoid pouring water onto the plants and avoid splashing water droplets; c. Avoid taking cuttings from diseased plants. If diseased leaves and branches are found, cut them off promptly and burn them; d. During periods of high temperature and humidity, spray 200-fold equal-amount Bordeaux mixture once every 2 weeks, for 3 consecutive times.

② Gray mold. This disease is mainly caused by overwatering, and the disease is even more severe in cold and humid conditions. It first damages the flowers, causing the edges of the petals to darken and wither. When air humidity is too high, a gray mold layer appears, and the small flowers twist and clump together. When affected petals fall onto the leaves, they can also cause disease in the leaves. Water-soaked brown lesions appear on the leaf surface, which shrink after drying and are covered with a light gray mold layer. Control measures: a. Remove diseased leaves and flowers promptly, avoid watering onto the plants, promptly remove moisture from the leaves and flowers, and always pay attention to ventilation and light exposure; b. In the early stage of the disease, promptly spray with 500-fold 75% chlorothalonil solution, for 3 consecutive times.