Bacterial leaf spot of geranium

Geranium, also known as hydrangea, into wax red, stone red. It originated in South Africa. Like cold and cool, afraid of high temperature, also not resistant to cold. Ask for plenty of sunshine. Not resistant to moisture, but slightly resistant to drying, should be well drained fertile loam. The weather is cool in spring and autumn, which is most suitable for the growth of geraniums. In winter, it is about 15 ℃ indoors during the day and no less than 5 ℃ at night. Keep enough light to bloom continuously. Summer is hot, the plant is dormant or semi-dormant, to place half-shaded place, pay attention to control watering. Resistant to chlorine. Pelargonium is an important potted flower. Cultivation is very common. There are two kinds of varieties: flower viewing and leaf viewing. Beijing, Shanghai, Northeast and other places are commonly used as spring and summer flower bed materials. It is a commonly used flower in the layout of flower beds on May Day. In areas where it is warm in winter and cool in summer, it can be cultivated in open field all the year round. Fragrant leaf geranium, chrysanthemum leaf geranium and aromatic geranium can be extracted for cosmetics and soap industry, and are often cultivated as cash crops.

Bacterial leaf spot of geranium is one of the most important diseases of geranium. Most of the leaves of susceptible plants died, resulting in defoliation, affecting the growth and flowering of geranium and reducing the ornamental value of the plant.

Symptoms: the disease mainly harms the leaves and sometimes the stems of the plants. In the early stage of the disease, the injured leaves produced needle-sized spots, the disease spots were round or irregular, brown and sunken, slightly showing wheel patterns. When the disease is serious, the diseased leaves are covered with disease spots. There are more spots on the older leaves in the lower part. After that, the disease spots expanded and gradually joined together, resulting in the death of most of the leaves. Finally, the diseased leaves fell off, the stem was black and rotted, and the whole stem of the susceptible plant blackened, wilted and rotted. When the stem is cut open, the vascular bundles turn brown and black. The disease is very serious on cuttings, and the cuttings begin to rot from the base and develop upward until the leaves wilt and die.

Pathogen: the pathogen is Xanthomonaspelargonii (Brown) StarretBurkholder.

Disease regularity: the pathogen survived in the disease part of the plant and spread by contact, splash of water droplets and cuttings. It can survive for three months in moist soil. The disease is serious in greenhouses where the density of young plants is high and the temperature is too high, especially in warm and humid weather. In this weather, there are many disease spots on the leaves of geraniums in the garden.

Prevention and treatment: ① reduces the source of infection: remove all infected leaves and destroy them centrally. ② strengthens cultivation management: avoid sprinkler irrigation to prevent the transmission of bacteria from one plant to another. Adjust the ventilation and reduce the humidity. The plants should not be too dense. Avoid splashing diseased soil on healthy plants. ③ chemical control: in the early stage of the disease, agricultural streptomycin was sprayed once every 10-15 days, 2-3 times.