Control Methods for Powdery Mildew in Coptis chinensis Cultivation

Coptis chinensis is afraid of high heat and prefers low temperatures, and prefers cool, shady and moist conditions. It is generally suitable for cultivation in areas at an altitude of 800 m--1500 m. In large-scale production, high temperature and high humidity in summer and autumn easily lead to widespread outbreaks of powdery mildew in Coptis chinensis, seriously affecting its growth and development.

The main symptoms of powdery mildew in Coptis chinensis are a layer of white-gray powdery material on the underside of the leaves, loss of green color on the upper side of the leaves, and the appearance of black markings. When the disease occurs at the seedling stage, it can cause the entire plant to die; when it occurs at the mature seedling stage, it can cause the leaves to dry up and the rhizome to stop growing, resulting in severe yield reduction of Coptis chinensis. Herb growers regard powdery mildew as the number one “enemy” in Coptis chinensis production, and it must be discovered early, controlled quickly, and thoroughly contained to prevent it from spreading and causing disaster. Herb growers in Chuanzhu Township, Emeishan City, have summarized comprehensive measures for controlling powdery mildew in Coptis chinensis through long-term production practice. The specific methods are as follows:

1. Plant ash can be used for prevention. Before sowing or transplanting, spread dry plant ash once on the seedling bed and the mature seedling planting site. After emergence and 1 month after transplanting, spread it again. The amount per mu is 30 kg at the seedling stage and 50 kg at the mature seedling stage.

2. Human urine diluted 10 times--20 times can be sprayed, using 4 kg--5 kg of urine per mu.

3. 50% carbendazim wettable powder diluted 500 times--800 times can be sprayed, using 200 g--250 g per mu. Control at the early stage of disease onset is best.

4. 50% thiophanate wettable powder diluted 500 times--800 times can be sprayed.

5. The microbial regulator Siluofu can be sprayed. At the seedling stage, use 10 g of the product mixed with 25 kg--30 kg of water per mu; at the mature seedling stage, use 20 g of the product mixed with 50 kg of water per mu for spraying.

6. Sulfur suspension concentrate diluted 200 times--400 times can be sprayed, using 150 g--200 g per mu.

7. Keshade 2000 wettable powder diluted 800 times--1000 times can be sprayed.

8. 0.6% Luwangjiu diluted 3000 times can be sprayed, which can help diseased plants resume normal growth and development. It can be mixed with the above-mentioned pesticides for a more pronounced effect. For scattered disease occurrences, the diseased leaves can be cut off and burned, combined with pesticide spraying for comprehensive control.

Precautions for pesticide use: generally choose cloudy days for spraying. If it rains within 4 hours after spraying, spray once more to ensure efficacy. The above-mentioned pesticides can be used alternately, choosing 2--3 types, which can effectively reduce the disease's resistance to the pesticides. Generally, spray once every 7 days--10 days, and 3 consecutive sprays can completely control powdery mildew in Coptis chinensis.