Common diseases of snapdragon and their prevention and control methods

Common diseases of snapdragon: seedling rot

Symptoms

Seedling rot is a serious seedling disease that can occur from seed germination to the entire seedling stage. The stems or roots of the seedlings near the soil surface begin to appear water-soaked, then gradually turn brown and shrink. In severe cases, the diseased parts rot, causing the entire plant to fall over or wither and die.

Prevention and treatment methods

During the seedling stage, the amount of watering should be controlled and the soil should not be too wet; sow seeds at the right time to prevent the seedlings from being affected by inappropriate temperatures; the seedlings should not be planted too densely and should be thinned out in time; keep the greenhouse ventilated and light-permeable, reduce the temperature between plants, and control the conditions for disease.

In addition, 70% pentachloronitrobenzene powder can be used to disinfect the soil. Use 5 to 8 g per m2 and mix it with an appropriate amount of fine sand before applying.

Common diseases of snapdragon: leaf blight

Symptoms

It mainly occurs in leaves and stems. When the leaves are infected, small water-like spots begin to appear on the leaf tips or edges, which then turn pale and gradually expand into round or irregular brown spots. There are brown irregular rings in the center of the spots and many small black spots scattered around.

The infected young leaves become twisted, and in severe cases the leaves shrink and die, hanging on the stems without falling off. The lesions on the stem are long and narrow or surround the stem, water-soaked, slightly sunken, grayish white in the center, and dark brown at the edges. The diseased parts often dry and crack, and have many small black spots, which are sometimes arranged in concentric rings. The stems are damaged during the seedling stage, often causing the seedlings to fall over.

Prevention and treatment methods

Strengthen cultivation management, remove diseased leaves or pull out diseased plants and burn them in time to reduce the initial infection source; pay attention to ventilation in the greenhouse, do not plant too densely, and do not apply nitrogen fertilizer excessively.

In the early stage of the disease, spray Bordeaux mixture or 600 times diluted 65% Zineb wettable powder.

Common diseases of snapdragon: blight

Symptoms

The disease is also known as stem rot, which mainly harms the stems and roots. After the pathogen invades the base of the stem, light brown spots are formed. The spots are water-soaked, constricted and rotten, and in severe cases often cause the plant to die. When the air humidity is high, white filaments may grow on the lesions.

Prevention and treatment methods

Remove diseased plants promptly and burn them to reduce the source of infection and lower the incidence rate. 2 to 3 weeks before planting, disinfect the soil with formalin, spray the soil with 30 ml of medicine at 50 times the dosage of water, then cover it with plastic film. Remove the covering after 5 days and wait for 1 to 2 weeks until the smell of the medicine has dissipated before use.

Common diseases of snapdragon: rust

Symptoms

It mainly harms the leaves, tender stems and calyx of snapdragon. The leaves become diseased with yellow-green blister-like water spots, which gradually expand. When the blister-like spots burst, reddish-brown summer spores are revealed, and the leaf tissue around the spots turns light yellow. Symptoms on young stems and calyx are similar to those on leaves. The affected plants grow weak and in severe cases the leaves scorch.

Prevention and treatment methods

When diseased leaves are found, remove and burn them immediately to prevent their spread; pay attention to ventilation and light transmission. In the early stage of the disease, spray 200 times diluted 15% triadimefon wettable powder or 400 times diluted 65% mancozeb wettable powder.

Common diseases of snapdragon: gray mold

Symptoms

It can harm the stems, leaves and flowers of the plant, mainly the flowers. Pathogens invade through weakened host tissues. The leaves are affected, often first at the tip or edge of the leaves. In the early stage of the disease, water-like spots appear on the diseased part, which gradually expand and the diseased tissue turns black-brown and rots.

After the bacteria invade, they can also cause infection of the pedicels and stems, resulting in ulcer spots. When the lesions surround the pedicels or stems, the flower spikes may wilt. Under humid conditions, the affected parts are covered with a gray-brown mold layer and often produce small black granular sclerotia.

Prevention and treatment methods

Remove diseased flowers and leaves promptly and burn them in a concentrated manner to reduce the source of infection. The greenhouse should be well ventilated, watering should not be excessive, and the indoor temperature and humidity should be controlled. Apply nitrogen fertilizer reasonably and increase phosphorus and potassium fertilizer appropriately to improve the plant's disease resistance. During flower management, try to avoid causing wounds to the plants to reduce the chance of infection by pathogens.

In the early stage of the disease, you can use 800-1000 times diluted 70% thiophanate-methyl wettable powder or 800-1000 times diluted 50% carbendazim wettable powder for spraying for prevention and control. Spray once a week, for 2 to 3 times in a row.