If the disease is severe, infected shoots should be pruned out, as they can also harbor the pathogen. Infected leaves are the primary source of inoculum and should be removed from the site.
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While little can be done about natural rainfall, avoid overhead irrigation of ornamental maples to reduce free moisture on the foliage. ManagementĪbundant rainfall in late April and early May often initiates maple anthracnose. Symptoms on twigs and buds are less common on maples but under high disease pressure, tender shoots may be killed. Many anthracnoe fungi have limited activity during mid-summer, when conditions are often drier and hotter. Spores are produced whenever environmental conditions allow (mild and wet) from spring through late-summer, but are typically most abundant in late spring and early summer. These readily form within leaf spots and blotches and can be found on the upper or lower leaf surface and along veins or midribs. Anthracnose fungi produce asexual spores (conidia) within pads of tissue known as acervuli. In the spring, fruiting bodies are produced and spores are spread by wind and splashing rainwater. Anthracnose fungi overwinter within senescent leaf tissue and in infected twigs and buds. On Japanese maple, lesions occur along primary veins and leaf margins and the lesions can appear both tan or black in color. On sugar maple, lesions occur along primary veins and appear as large, brown blotches. Lesions on Norway maple tend to be narrow, purplish-black streaks along leaf veins. Symptoms can vary by host and fungal pathogen present, but in general the symptoms are characterized by dark-colored, irregularly-shaped, angular spots or blotches that occur primarily along the midrib, primary veins and leaf margins. Young trees that are recently transplanted are more susceptible to lasting damage while older, established trees typically suffer only minor growth losses. Healthy trees that are defoliated early in the growing season are often able to flush a new set of foliage and recover. Under ideal environmental conditions, the disease can be more serious, leading to premature defoliation and contributing to the decline of stressed and weakened trees. Maple anthracnose is often a minor disease that only reduces the aesthetic value of infected trees. HostsĪll native and non-native maples commonly planted as woody ornamentals are susceptible to infection. Kabatiella apocrypta), Discula campestris and Colletotrichum gleosporoides. Several fungal pathogens are responsible for maple anthracnose in southern New England, including: Aureobasidium apocryptum (syn.
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