What are the latest control methods for strawberry powdery mildew?

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

Symptoms of strawberry powdery mildew

Strawberry powdery mildew mainly affects leaves, petioles, flowers, flower stalks 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 dark discolored spots of varying sizes appear. The spots then gradually expand, and a thin frost-like white powdery substance forms on the underside of the leaves. 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 buds fail to open. When fruit is infected, the young fruit cannot swell 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 to 25°C, the suitable temperature for conidial production and infection is around 20°C, and the relative humidity is above 90%. If from late autumn to early spring there is continuous cloudy, rainy, foggy or snowy weather with little sunshine, low temperatures and high relative humidity, this favors the continuous production of spores and repeated infection, causing the disease to break out and become 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 usually first appears in mid-October, while in the latter the disease center only appears 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 phosphorus and potassium fertilizers are added, the disease is milder.

How to treat strawberry powdery mildew?

1. Before flowering and before the disease appears, use protective fungicides for prevention twice, spraying with 2% Wuyi mycin aqueous solution at 200 times dilution or 75% chlorothalonil wettable powder at 600 times dilution, once every 7 to 14 days. Alternating the agents gives better results.

2. After the disease appears, choose agents with protective and curative effects for control, using 50% kresoxim-methyl water-dispersible granules at 3000 times dilution or 4% tetraconazole aqueous solution at 1000 times dilution, spraying once every 7 to 10 days. Alternating use gives better results.

Prevention of strawberry powdery mildew

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

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

3. Promptly remove old leaves, diseased leaves and residual leaves, and do a good job of field sanitation management.

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

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