Planting Tips

Chapter 54 What are the common fungal diseases of flowers and how to prevent them
(1) Types of fungal diseases Fungal diseases are the most common type of flower diseases.Fungi are low-level organisms that do not have chlorophyll, use mycelium as a vegetative body, and reproduce with sporophytes.Diseases caused by fungal infections are called fungal diseases.Fungal diseases generally have obvious symptoms, such as powder (white powder, etc.), mold (black mold, gray mold, penicillium, green mold, etc.), rust, granular, filamentous, nuclear Objects etc.The above characteristics are one of the main basis for identifying fungal diseases.Common fungal diseases of flowers include powdery mildew, anthracnose, gray mold, rust, blight, damping-off, black spot, brown spot, mildew, soot, root rot, and sclerotinia And so on.

Here are several fungal diseases of flowers that are widely distributed and harmful.

①Powdery mildew: The bacteria grows on the tender buds, young leaves, flower buds and pedicels. In the early stage of the disease, chlorotic spots appear on the affected parts, which gradually turn into white powdery spots, such as covered with a layer of white powder. into gray.Affected leaves and stem tips are curled, shrunken, and deformed, and flowers are small and few or cannot be opened normally.The germ spores spread with the airflow, and the spread is most likely to occur in the greenhouse.It mainly harms rose, chrysanthemum, plum blossom, dahlia, cineraria, fuchsia and other flowers.

②Anthracnose: It mainly harms the leaves, and can also harm young stem tips, flower buds, fruits and other parts.After most of the flowers are infected by the pathogen, the disease starts from the tip and edge of the leaf, and nearly round lesions appear on the leaf surface. The edges of the lesions are mostly dark brown, and the center is light brown or off-white. Spots, often arranged in a ring pattern, when the disease is severe, the leaves die.Anthracnose mainly harms orchids, clivia, camellias, plum blossoms, figs, rubber trees, cyclamen, hydrangeas, evergreens, etc.

③ Botrytis: Mainly damage leaves, stems, flowers and fruits.The host is different, and the damaged parts and degrees are also different.Generally, water-soaked spots appear at the beginning of the onset, and gradually expand later, turning into brown or purple-brown lesions. When the weather is humid, gray fuzzy things grow on the lesions, and when the disease is severe, the pruning dies.

④ Black spot disease: The pathogen lurks in the soil, invades the lower leaves with the splash of rainwater, and spreads upward rapidly.

Affected leaves first appear black spots, and then gradually expand into round, oval, and continuous sheets.Diseased leaves are chlorotic and fall off.The onset is usually more rapid during the rainy season from July to August.It mainly harms roses, roses, plum blossoms, chrysanthemums, peonies, geraniums, white orchids, cannas and other flowers and trees.

⑤ Brown spot disease: Near round dark brown or brown lesions appear on the leaves of the affected plants, causing a large number of burnt leaves in severe cases.The disease mainly harms peony, peony, chrysanthemum, rhododendron, camellia, osmanthus, poinsettia, gerbera, rose, geranium, etc.

⑥ Seedling blight: Seedling disease caused by Fusarium, Rhizoctonia, and Pythium. The symptoms are rot, damping, and blight, and the seedlings suffer the most within 20 days after being unearthed.The common ones are gladiolus, carnation, cineraria, chrysanthemum blight and so on.

⑦ Rust: Rosaceae flowers and carnations are mostly affected.Mainly damage leaves, stems and buds.Orange-yellow blister-like protrusions appear on both sides of the affected leaves, and orange-red powder is released after rupture. This is the uredia spore of rust, which will repeatedly infect the plant.The spores shed in late autumn and early winter are chestnut brown, and they are teliospores of rust fungi, which will infect leaf buds and other lesions in spring.Cupressaceae plants are the host plants for rust, and flowers should not be planted with such plants, otherwise the disease will be more serious.

(2) Prevention and control methods of fungal diseases of flowers
① During the growth period of flowers, from the approaching onset period, spray 7% ​​zinc or mancozeb wettable powder 10-65 times every 400-600 days, and spray 3-5 times continuously to inhibit the occurrence of diseases spread.

②Strengthen cultivation management, fertilize and water rationally, pay attention to ventilation and light transmission, and cool down in summer to make the plants grow robustly and improve disease resistance.

③ Thoroughly remove litter and fallen leaves in winter and spring; cut off diseased branches, leaves, buds, etc. in time after the onset of the disease, and destroy them in a centralized manner to reduce the source of bacteria.

④ Spray 50% carbendazim (or thiophanate) 500-800 times liquid at the early stage of the disease, or 75% chlorothalonil 600-800 times liquid.Botrytis cinerea can also be mixed with 70% pentachloronitrobenzene and 80% zinc in equal amounts, and 8-10 grams per square meter can be used for soil disinfection.In addition to the use of soil disinfection and chemical control to prevent and control seedling blight, when the seedlings are unearthed for about 20 days, strict control of watering and proper ventilation are the key to the prevention and control of blight.When rust is found, the diseased leaves should be cut off and burned, and sprayed with 40% fenxienin 4000 times solution or dirust sodium 300 times solution for prevention and treatment.

(End of this chapter)