Strawberry plants are very sensitive to temperature and moisture. This means that they can be challenging to grow, especially in gardens that are slightly shady or in climates like the Pacific Northwest, a rainy and cool area. When strawberry plants are exposed to cool, damp conditions, they are more likely to get powdery mildew. Powdery mildew is caused by a number of different fungi. It makes strawberry leaves and stems appear white and gradually spreads up and down the plant.
The best treatment for powdery mildew is to avoid it altogether by keeping the strawberry leaves dry. Choose a warm, dry location for strawberry plants. Water in the morning and try to water from underneath using an irrigation system. Powdery mildew begins to thrive when plants' leaves get wet, especially when the dampness stays on the plant overnight.
Remove Infected Foliage
Check your strawberry plants regularly for powdery mildew. It is especially important to look for this mildew as the summer comes to a close. When the days begin to get cooler and night falls earlier, the conditions are right for mildew. Powdery mildew begins as a white spot of powder that spreads into a film of white powder all over the plant. It stunts the growth of the plant.
If you find a leaf with mildew, remove the leaf from the garden. If you find a plant that is infected, get rid of the plant. Powdery mildew spreads easily throughout the garden.
Use Nontoxic Plant Sprays
If powdery mildew continues to spread and the entire strawberry patch becomes covered in mildew, spraying with a nontoxic plant spray will keep the strawberry plants going until you can harvest your ripe berries. Mix 1 tsp of baking soda with 1/2 tsp of horticultural oil. Place the mixture into a 1-quart spray bottle and fill it to the top with water. Shake the mixture and spray it on the tops and bottoms of the strawberry leaves. This should stop the mildew from spreading.
Apply the spray to the plants no more than once a day, as soap is not good for the soil and for animal life. Wash berries thoroughly before eating.