Prevention and treatment of powdery mildew of rose

Rose powdery mildew is a kind of fungal disease, which harms rose, Rosaceae and other flowers. it first infects in mid-late May and spreads in June and July. after the damage, there is a layer of white powder on the leaf surface and tender shoots, and when the leaves turn yellow and fall off seriously, it seriously affects plant growth and flowering. Let's take a look at the prevention and control methods of rose powdery mildew.

Harmful symptoms

Powdery mildew harms leaves, tender shoots, buds and pedicels of rose. After the young leaves were infected, the leaves shrunk, curled and deformed, sometimes turning purplish red. After the old leaves were infected, nearly round, watery chlorotic macula appeared on the leaf surface, which had no obvious boundary with healthy tissue, and there was a white substance on the back of the leaves. When seriously injured, the leaves withered and fell off. The injured parts of tender shoots and pedicels were slightly enlarged, and the top of them bent to the ground. The flower bud cannot open after being infected, or the flower posture is abnormal. The surface of the affected area is covered with a layer of white powder, which is a typical feature of powdery mildew.

Occurrence regularity

Powdery mildew is generally easy to occur in warm, dry or humid environment, but rainfall is not conducive to the occurrence of the disease. The disease is easy to occur when too much nitrogen fertilizer is applied and the soil is lack of calcium or potassium fertilizer, the plant is too dense, the ventilation and light transmission is poor, and the disease is serious. Drastic changes in temperature and over-dry soil in flowerpots will reduce the swelling and pressure of host cells, which will weaken the disease resistance of plants and be conducive to the occurrence of diseases.

Prevention and cure method

1. Strengthen cultivation management and pay attention to soil moisture and timely watering. When growing in greenhouse, ventilation should be increased so that the humidity is not too high. Reasonable fertilization, nitrogen fertilizer should not be too much, should be properly increased potassium, calcium fertilizer, in order to enhance plant growth, maintain a strong plant, itself to resist the invasion of miscellaneous bacteria in natural cultivation techniques.

2. Timely pruning and shaping, removing diseased shoots and leaves, and improving ventilation and light transmission between plants. Indoor potted rose should be placed in a place with good ventilation and sufficient light. Pruning and destroying all dead susceptible branches in early spring can reduce the source of infestation. Early diseased leaves should be removed as soon as possible.

3. Spraying should be comprehensive and thoughtful when using pesticides, protect the young parts, and increase the spraying times during the peak growth period and rainy season of new shoots. At the beginning of the disease, you can choose 1500 times solution of 15% Jingning wettable powder, or 2000 times of 20% trimethoprim EC, or 2000 times of 50% multi-flow suspension, or 50% methyl topiramate wettable powder and 75% chlorothalonil wettable powder, spray once every 7 days. Spray 2 times in a row for 3 times.