How to treat strawberry powdery mildew? Detailed control methods

Strawberry powdery mildew is a major disease in strawberry production. It can occur throughout the entire growing season of strawberries. Infection at the seedling stage causes a decline in seedling quality, making it difficult for the plants to survive after transplanting. Infection of the fruit seriously affects strawberry quality, leading to a drop in the marketable rate and severely affecting strawberry yield, quality and economic returns. Let us take a look below at how to treat strawberry powdery mildew!

Symptoms of strawberry powdery mildew

Strawberry powdery mildew mainly harms leaves, petioles, flowers, pedicels and fruit, and rarely occurs on runners. When leaves are infected, in the early stage of the disease a thin layer of white mycelium grows on the underside of the leaves; as the disease worsens, the leaves curl upward into a spoon shape and develop dark discolored spots of varying sizes; afterward the spots gradually expand and a thin frost-like white powdery substance appears on the underside of the leaves, and in severe cases multiple spots join together to cover the entire leaf. When flower buds and flowers are infected, the petals turn pink and the flower buds fail to open. When fruit is infected, the young fruit cannot expand normally and dries up.

Causes of strawberry powdery mildew

1. Strawberry powdery mildew is a low-temperature, high-humidity disease. The suitable temperature for onset is 15-25°C, and the suitable temperature for conidia production and infection is around 20°C, with relative humidity above 90%. If from late autumn to early spring there is continuous cloudy, rainy, foggy, snowy or other weather with little sunshine, low temperature and high relative humidity, this favors the continuous production of spores and repeated infection, causing the disease to break out into a disaster.

2. Strawberries grown in greenhouses with continuous cropping develop the disease earlier and more severely, with the first appearance of the disease about 1 month earlier than in newly built greenhouse plots. In the former, the disease mostly begins in mid-October, while in the latter the first disease focus appears only in mid-November. Fertilization is closely related to the disease: excessive application of nitrogen fertilizer makes strawberry plants grow vigorously, with large, tender green leaves that are prone to powdery mildew. If nitrogen fertilizer is applied at the right time and in the right amount, and phosphate and potassium fertilizers are added, the disease is milder.

How to treat strawberry powdery mildew?

1. Before flowering, when the disease has not yet occurred, use protective fungicides for two preventive applications: spray with 2% Wuyi mycin aqueous solution at 200 times dilution or 75% chlorothalonil wettable powder at 600 times dilution, once every 7-14 days; alternating the agents gives better results.

2. After the disease occurs, choose agents with protective and therapeutic effects for control: use 50% kresoxim-methyl water-dispersible granules at 3000 times dilution or 4% tetraconazole aqueous solution at 1000 times dilution, once every 7-10 days; alternating use gives better results.

Prevention of strawberry powdery mildew

1. Choose disease-resistant varieties and cultivate disease-free strong seedlings.

2. Practice reasonable crop rotation to reduce the occurrence of the disease.

3. Remove old leaves, diseased leaves and residual leaves in a timely manner, and do a good job of field sanitation management.

4. Irrigate reasonably, control the humidity inside the greenhouse, and reduce the disease.

5. Reasonably control the amount of nitrogen fertilizer and apply more phosphate and potassium fertilizers.