Ivies are climbing, woody evergreen vines commonly found scaling up walls and trees. They're also popular indoor plants used to beautify homes and offices, as well as purify air. Two of the most widely grown ivies are Boston ivy and English ivy. Although most types of ivy are disease resistant, sometimes fungal and bacterial diseases can cause ugly spots on leaves, as well as cankers, which are dead segments on branches or stems.
Leaf spot caused by the fungus Amerosporium trichellum mostly attacks English ivy, rather Boston ivy. This fungal disease has symptoms of circular or oval brown spots on both outer and inner leaf surfaces. Other signs of the fungal disease are small black spots interspersed throughout a leaf. When stems are infected, they become girdled, resulting in the stems collapsing and then dying. Keeping foliage as dry as possible can control leaf spot. The Mississippi State University website recommends watering early in the day so there’s enough time for leaves to dry.
Powdery mildew, a fungal disease, mostly afflicts Boston ivy. Signs of this disease are white, powdery patches developing on the upper surfaces of leaves and sometimes stems. Signs of the disease are often more visible in hot weather. Leaves that are heavily infected turn brown and then shrivel. The odds of contracting this disease can be reduced by not spacing Boston ivy plants too closely together. All infected leaves should be discarded in a plastic bag to prevent fungal spores spreading to other plants. Fungicides are not needed.
Scab is a fungal disease that generally afflicts English ivy. It’s caused by the fungus Sphaceloma hederae and occurs as “scabby” brown circular spots that are scattered over a leaf and sometimes its veins. When these spots accumulate, they typically run together to form one large mass. Lower leafs may have spots that are somewhat sunken in the middle with the upper leaf surfaces having spots forming a purple border.
Guignardia Leaf Spot
Guignardia leaf spot is a common leaf spot fungal disease that attacks young leaves of Boston ivy. It’s caused by the fungus known as Guignardia bidwelii, which is the same pathogen that also causes leaf spot. Symptoms of Guignardia leaf spot are circular or angular rough spots on leaves. Normally, these spots have a purplish-red border. When this infection occurs prior to leaves being fully expanded, leaves become wrinkled and distorted. Cool and moist conditions can create a favorable environment for fungal spores to be produced.
Bacterial Leaf Spot
Bacterial leaf spot is a bacterial disease caused by the bacterium Xanthomonas hederae. This disease, which inflicts English ivy, begins with light green water-soaked spots appearing on leaves. As these spots enlarge, they turn brown or black, creating red margins on leaves. Cankers can form on stems and girdle them, causing a bacterial dripping when the weather is moist and warm.
- Mississippi State University: Landscape Tips for Disease Control in Ivy
- University of Illinois Extension: Reports of Plant Diseases
- West Virginia University Extension Services: Diseases of English Ivy
- Cornell University: Boston Ivy Disease Factsheet
- The Connecticut Agricultural Experiment Station: Boston Ivy (Parthenocissus)