There are many causes of diseases in flowers, but they can be broadly divided into two categories: One category is caused by maladaptation to external environmental conditions, known as non-infectious pathogens. These diseases are caused by poor cultivation conditions, such as excessive or insufficient water, excessive or insufficient light, excessively high or low temperatures, excessive or insufficient fertilizer, nutrient deficiencies or imbalances, and pollution from smoke, dust, and harmful gases. These are also called physiological diseases. These diseases affect the growth and development of flowers but are not contagious. The other category is caused by biological infection, known as infectious pathogens, such as fungi, bacteria, and viruses that attack the plant. Among these, fungal infections are the most common. These diseases can spread rapidly and infectively under suitable environmental conditions.

Symptoms and treatment methods of physiological diseases in flowers

(1) The branches are slender. The internodes are relatively long, and the leaves are pale, thin and weak. This is due to insufficient light. The amount of sunlight should be increased. If the weather is cloudy and rainy for too long, the amount of light can be increased artificially, that is, by using artificial light to illuminate it.

(2) The lower leaves of the plant are curled, the branches and leaves grow slowly, and the leaves have scorched edges. This is caused by excessive sunlight. Appropriate shading should be provided. If it is a potted plant, it can be moved to a shade structure for a period of time.

(3) The leaves wither, the lower leaves of the plant fall off, and the leaf tips turn yellowish-brown. This is due to lack of water. Water thoroughly each time, and do not water only halfway. Water according to the principle of watering only when dry and watering thoroughly.

(4) The branches and leaves wither, the leaves darken and gradually become moldy. This is caused by overwatering. The number of times and amount of watering should be controlled. Check whether the drainage holes at the bottom of the pot are blocked and ensure that the drainage is smooth.

(5) The leaves are wrinkled and yellowish-brown. This is due to insufficient humidity. You should spray water on the leaves of the plant and spray water on the ground around the potted plant to increase the humidity of the ambient air.

(6) If the leaves turn yellow, curl, or wither, it is due to excessively high temperature. The potted plant should be moved to a cool and ventilated place for maintenance, and water should be sprayed or sprinkled on the plant and its surroundings frequently to lower the temperature.

(7) The leaves and stems grow excessively, the plant produces few buds and does not flower, and moss appears in the clay pot. This is caused by excessive use of nitrogen fertilizer. The frequency and amount of fertilization should be reduced, nitrogen fertilizer should be reduced, and phosphorus and potassium fertilizer should be applied more.

(8) The growth of all parts of the plant is slow and stagnant. The lower leaves of the plant droop and are pale in color. This is due to lack of fertilizer. The frequency and amount of fertilization should be increased during the growth period.

(9) Yellow-brown spots appear on the leaves. This is caused by sunburn. You should immediately pay attention to shading or move the flower pot to a semi-shaded place to avoid direct sunlight.

(10) White crystals appear on the surface of the potting soil and the edge of the flowerpot. The plant leaves wither, rot, and fall off. This is caused by excessive application of chemical fertilizer. Water should be applied first to dissolve the white crystals. After 1 hour, water should be applied again to dilute the chemical fertilizer in the soil.

(11) During the overwintering period, white or light yellow spots appear on the leaves of the plant. This is caused by cold water droplets dripping onto the leaves. You can spray some water that is slightly higher than the room temperature onto the leaves.

(12) The pot is full of exposed fibrous roots, and fibrous roots also emerge from the drainage hole at the bottom of the pot. The leaves are prone to shrinkage, and there are few and small new leaves. This is caused by not repotting for many years or the flower pot is too small. In spring, a larger flower pot and more new soil should be used, and some base fertilizer should be applied to the bottom of the pot. Some of the excess fibrous roots should be trimmed.

Common fungal diseases of flowers

Fungal diseases are numerous and constitute one of the most important categories of diseases. Fungi are extremely small and cannot produce their own nutrients. They use mycelium as a nutrient source and reproduce via spores. They typically absorb nutrients from the plant through mycelium. Fungi have multiple modes of transmission; their spores can be spread widely by wind, rain, and insects. Common types of fungal diseases affecting flowers include the following:

powdery mildew

The pathogen is epiphytic on the buds, tender leaves, shoots, and flower stalks of flowers. In the early stages of the disease, chlorotic spots often appear on the affected areas, which gradually turn into white powdery spots, as if covered with a layer of white powder. In the later stages, they turn gray. Affected leaves and shoots curl, wither, and become deformed, and flower buds cannot open normally. The spores of the pathogen can be spread by air currents. It is most likely to occur on a large scale when the temperature difference between day and night is 10℃, and it spreads most easily in greenhouses. This disease often occurs on impatiens, roses, cineraria, plum blossoms, fuchsias, and dahlias.

Black spots

This disease is also one of the common diseases of flowers. The pathogen lies dormant in the soil and often enters the lower leaves of flowers with rainwater splashing down. It spreads rapidly upwards, and black spots appear on the affected leaves, which gradually expand into round or oval shapes and connect into patches. Diseased leaves wither and fall off. The disease usually occurs most frequently during the plum rain season in July and August, and has a great impact on the growth of flowers. Commonly affected flowers include roses, Chinese roses, chrysanthemums, plum blossoms, peonies, azaleas, magnolias, geraniums, and cannas.

Anthrax

This disease primarily affects leaves, but can also damage young stems, buds, and flower buds. Symptoms include: one type presents as light brown or gray circular spots with purplish-brown or dark brown edges on leaves, which can cause most leaves to wither and die in severe cases; another type presents as circular or nearly circular or concentric lesions on the stems, light brown or grayish-white with small black dots. During the rainy season, cacti and other plants are most susceptible, and it also commonly affects plum blossoms, camellias, clivias, hydrangeas, rubber trees, orchids, cyclamen, and evergreen plants.

Sooty mold

This disease affects the branches, leaves, and fruits of many flowers. The pathogens are various fungi, and scale insects and aphids are the main vectors for transmission. During the infection period, brown mold spots appear on the leaf surface, which gradually expand to form a black sooty mold layer, preventing the plant from photosynthesizing and producing nutrients, causing it to wither and die.

These are some suggestions and thoughts from the editor regarding the prevention and control of flower diseases and pests. Different flower lovers will receive targeted guidance. Finally, I hope everyone can experience a different kind of ease in the process of growing flowers, and I also hope that with the help of the editor, everyone can have a smooth journey in the process of caring for flowers.