Control methods of powdery mildew of balsam pear

Balsam pear powdery mildew is common in balsam pear plants, different varieties have different resistance to powdery mildew, mainly in leaves, followed by petioles and vines, the disease is caused by fungal monofilament infection, it is an idiopathic parasitic bacteria, can only live parasitic life, the symptoms are mainly harmful leaves, let's take a look at the prevention and control methods of balsam pear powdery mildew.

Harmful symptoms

At first, small round powdery mildew spots grew on the front or back of the lower leaves of the plant, which gradually expanded and thickened, and soon became one. In the later stage of the disease, the whole leaf was covered with white powder, then turned grayish white, and finally the whole leaf became yellowish brown and dry. Most of the diseases began from the middle and lower leaves, and then gradually spread to the upper leaves.

Disease condition

The pathogen can survive the winter on melons, vegetables, roses and other flowers in the greenhouse, and produce conidia after overwintering, which can be spread by air flow. The pathogen takes more than 20 hours from spore germination to invasion, so the disease develops rapidly and often spreads in a short time. All the bacteria could move at 10: 30 ℃, and the optimum temperature was 20: 25 ℃. The onset of the disease is quick when the relative humidity is 45-75%, and can also be caused by conidia germination when the relative humidity is less than 25%. When the relative humidity exceeds 95%, the disease is significantly inhibited.

Prevention and cure method

The main results are as follows: 1. Balsam pear powdery mildew prevention and control should be carried out first by rotation, not with cucurbitaceae vegetables, and before sowing, the soil-proof layer of new high-fat film on the ground should be hardened to isolate the source of diseases and insect pests and improve the emergence rate.

2. Soak balsam pear seeds in warm water of about 55 ℃ before sowing, continue soaking seeds for 12 hours after natural cooling, and apply new high-fat film before sowing to ward off underground diseases and insects, strengthen respiratory intensity and improve seed germination rate.

3. Different balsam pear varieties have different resistance to powdery mildew. Generally, the resistance of early-maturing varieties is weak, while that of middle-late-maturing varieties is strong. Attention should be paid to the cultivation of strong seedlings, reasonable close planting, timely pruning and leafing, improving ventilation and light transmission conditions, so as to make plants grow healthily and improve disease resistance.

4. The commonly used agents of balsam pear powdery mildew are 15% trimethoprim wettable powder, or 20% trimethoprim EC 2000 times 3000 times, or 50% carbendazim wettable powder 500 times, or wettable sulfur powder 300 times, or 75% chlorothalonil wettable powder 600 times 800 times.

5. In the greenhouse, chlorothalonil smoke remover is used to treat both downy mildew and powdery mildew. When spraying, it should be sprayed evenly on the middle and lower old leaves and the back of the leaves. In the initial stage of the disease, it should be sprayed once every 7-10 days for 2 times in a row, which can achieve a better control effect.