Powdery Mildew is a fungal disease that affects a wide range of plants. Powdery mildew infection is caused by many different species of fungi in the order Erysiphales. It is one of the easier diseases to spot, as its symptoms are quite distinctive. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. It is important to be aware of powdery mildew and its management as the resulting disease can significantly reduce crop yields.
HOST PLANTS: Common in many different types of plants. Zucchini, roses and zinnia are especially susceptible.

SYMPTOMS: Powdery mildew starts on young leaves as raised blister-like areas that cause leaves to curl, exposing the lower leaf surface. Infected leaves become covered with a white to gray powdery growth, usually on the upper surface; unopened flower buds may be white with mildew and may never open. Leaves of severely infected plants turn brown and drop. The disease prefers young, succulent growth; mature leaves are usually not affected.

FAVORED ENVIRONMENT: Low soil moisture combined with high humidity levels at the plant surface favors this disease.

POWDERY MILDEW CONTROL: For powdery mildew control, plant resistant cultivars in sunny areas whenever possible. Prune or stake plants to improve air flow in the plant. Remove the fallen and diseased foliage off the plant and from the ground. Make sure to disinfect your pruning equipment (one part bleach to 4 parts water) after each cut. Use a thick layer of mulch to coat the soil after you have raked and cleansed it well. The mulch will stop the fungus spores from splashing back up onto the foliage. Washing leaves occasionally in mid-morning may interrupt the daily spore-releasing cycle. Water only in the morning so plants have a chance to dry during the day. Drip irrigation and soaker hoses will help keep the leaves dry. Apply sulfur based fungicides or copper-based fungicides weekly to prevent infection of susceptible plants.

Products for Powdery Mildew Control


Sulfur Fungicide Greencure Biofungicide (8 oz) Mycostop Biofungicide