How to Manage Pests
Pests in Gardens and Landscapes
Downy mildew of roses—Peronospora sparsa
Downy mildew causes purplish, red, or dark brown spots on leaves. Leaf undersides are covered with downy
fungal growth. Leaves may yellow and drop. The fungus that causes downy mildew on roses produces spores only on living plants. Resistant spores
carry the fungus over unfavorable periods. Downy mildew is favored by moist, humid conditions.
to improve air circulation. Reduce humidity around plants, by using, for instance, drip or low-volume
irrigation. Avoid overhead watering. Fungicide applications help prevent damage.
spots on rose leaf