The Fungus Control for Miniature Roses

Common Diseases

• The most common disease to miniature roses is powdery mildew which presents as a white to gray powdery coating on the undersides and tops of rose leaves. Black spot appears as brown to black irregularly-shaped blotches throughout the shrub. Rust appears as an orange to red coating on the leaves. Botrytis causes total decline in the miniature rose.Downy mildew causes leaves to turn yellow and fall off. Anthracnose causes red to purple lesions in the leaves which fall out and cause holes in the leaves. All of these are caused by fungal pathogens.

Controls

• No single fungicide controls all types of fungal diseases. Powdery mildew can be controlled by using fungicides containing the active ingredients triadimefon, triforine or fenarimol. Black spot can be controlled with fungicides containing folpat, captan, mancozeb or chlorothalonil. Rust diseases can be controlled by using fungicides containing triforine, mancozeb or chlorothalonil. For those wishing to use organic or non-synthetic fungicides, sprays containing horticultural oils, neem oil or potassium-bicarbonate can be used at regular intervals.

Prevention

• Proper site selection for the planting of miniature roses and routine maintenance will reduce the chance for most fungal diseases. Select a site that is open so that there is good air circulation and that receives at least half of a day of full sun. Plant in soil that drains well. Avoid watering miniature roses overhead, instead water at the soil level. Prune out dead and diseased canes as they occur and thin out your miniature roses every year by up to a third by removing the older canes in early spring.

Resistant Varieties

• No miniature rose is completely immune to fungal diseases. There are however several disease-resistant varieties available which can help to reduce the incidence of common diseases, especially black spot. According to both Purdue University and the Ohio State University, they include such cultivars as: "Always a Lady", "Angel Darling", "Anytime", "Apricot Twist", "Baby Betsy McCall", "Beauty Secret", "Black Jade", "Centerpiece", "Cinderella", "Cuddles", "Deep Velvet", "Green Ice", "Gourmet Popcorn", "Jennifer", "Linville", "Little Artist", "Loving Touch", "Magic Carrousel", "Minnie Pearl", "Old Glory", "Pacesetter", "Queen City", "Rainbow's End", "Red Cascade", "Red Flush", "Rose Gilardi", "Simplex", "Singles Better", "Sweet Pickins", "Watercolor" and "Work of Art."