How are edible mushrooms cultivated? A detailed explanation of common parasitic diseases of flowers

(1) Fungal diseases Fungal diseases are the most important category among flower diseases. Fungi are lower plants without chlorophyll and are invisible to the naked eye. They cannot make their own nutrients and absorb nutrients within the flower plant through mycelium. Fungal spores spread everywhere by wind, rain, insects, and other means. Common fungal diseases of flowers include:

Powdery mildew: The pathogen grows on buds and tender leaves, producing a white mold layer. The affected leaves and shoot tips curl, shrink, and become deformed, and the flower buds cannot open normally. The pathogen spores spread and proliferate with airflow. It is most likely to break out over a large area when the day-night temperature difference is 10°C, and it spreads most easily in greenhouses. Examples include powdery mildew on rose, fuchsia, plum blossom, garden balsam, cineraria, and dahlia.

Black spot: This is a common flower disease. The pathogen lurks in the soil, splashes down with rainwater to invade the lower leaves, and then spreads rapidly upward. Affected leaves first show black spots, which gradually enlarge into round or oval shapes and then merge into patches. Diseased leaves turn yellow, wither, and fall, greatly affecting flower growth. It usually develops rapidly during the rainy season in July-August. Common examples include black spot on rose, chrysanthemum, tree peony, and geranium.

Black rust: When infected by pathogen spores, pale white small spots first appear on the upper surface of the leaves, gradually swell into slightly round protrusions, and then the lower epidermis ruptures and produces orange-yellow powder that flies away with the wind and infects large areas. Afterwards, dark ink-colored oval spots appear on the leaves, and after the lower epidermis ruptures, black powder is produced again. In severe cases, the entire plant becomes diseased from bottom to top, the leaves scorch and dry up, and they fall early. Common examples include black rust on rose, iris, and multiflora rose.

Seedling damping-off disease: A seedling disease caused by Fusarium, Rhizoctonia, and Pythium. The symptoms include rot, damping-off, and seedling blight, with the heaviest damage occurring within 20 days after the seedlings emerge. Common examples include damping-off disease on gladiolus, lily, begonia, and carnation.

Anthracnose: It mainly damages leaves, and can also damage stems. One form appears on leaves as nearly round spots that are light brown or grayish white with purplish-brown or dark brown edges. These spots often occur at the leaf margin or leaf tip, and on them are small black dots, namely the pathogen's acervuli. In severe cases, more than half of the leaf becomes withered and black. Examples include anthracnose on orchid grass, and it is also commonly seen on white orchid, rubber tree, cyclamen, hydrangea, and other flowers. Another form produces round or nearly round lesions on stems, light brown in color, with small black dots on them. Examples include anthracnose on cacti, which is severe during the plum rain season or when autumn rains continue. Control method: Pay attention to light transmission and ventilation for potted flowers in daily care, and do not place them too densely. When only a few leaves are affected, the diseased leaves can be cut off and burned. In severe cases, spray a 500-1000 times solution of 50% carbendazim wettable powder, or a 500 times solution of 50% thiophanate-methyl wettable powder, for a relatively good control effect.

Sooty mold: It damages the branches, leaves, and fruits of many flowers and trees. The pathogens are multiple fungi. They mostly use aphids or scale insects as vectors for spread. In the early stage, dark brown mold spots appear on the surface, gradually expand, and form a black sooty mold layer, hindering the plant's photosynthesis so that the plant cannot make nutrients and withers and dies. Control method: First control aphids and scale insects. If sooty mold has already occurred, it can be controlled in summer with 0.3-degree Baume lime sulfur mixture, in winter with 3-degree, and in spring with 1-degree lime sulfur mixture; it can also be controlled with the carbendazim and thiophanate-methyl mentioned in the previous example.

In addition, there are also root rot, leaf spot, and other diseases.

(2) Bacterial diseases Bacteria are very small single-celled organisms without differentiation into vegetative and reproductive bodies. They absorb nutrients through the cell membrane and reproduce by division. Bacterial infection mainly occurs through stomata, nectaries, wounds, and other routes, and is generally spread by flowing water, wind and rain, insects, soil, and diseased plant residues. Common bacterial diseases include crown gall on rose and elm-leaf spirea, and citrus canker.

(3) Viral diseases Viruses are extremely tiny parasites that can only be seen with an electron microscope, and viruses reproduce only in living flower cells. Viruses are transmitted through insects (mainly insects with piercing-sucking mouthparts, such as aphids and red spiders), grafting, mechanical injury, and other routes. Symptoms include mosaic, yellowing, leaf curling, deformity, rosetting and dwarfing, necrosis, and spots. Common examples include mosaic disease and rusty fruit disease on rose and begonia.