Ornamental & Tree Diseases
Sycamore Anthracnose
This fungus-caused (Gnomonia platani ( = Gloeosporium platani)) disease was first described on sycamores in 1848 and remains endemic throughout the range of the sycamore. Disease impact tends to be underestimated, because repeated attacks by the fungus over 2 or 3 years can seriously weaken trees and predispose them to other stress agents.
Diagnostic symptoms include leaf blight, which begins as small brown spots that elongate and coalesce into large, brown necrotic areas along veins, midribs, and leaf margins, shoot blight, and twig blight which usually appears in the spring when leaves are emerging and commonly results in death of 1-year-old twigs. The repeated killing of twigs stimulates development of new branches at bases of dead twigs, imparting a "witches-broom" appearance to infected trees. Cankers (sunken necrotic areas surrounded by callus ridges) are commonly found on infected stems and twigs. Defoliation is also diagnostic.
The anthracnose fungus overwinters as mycelium and acervuli in stems and twigs and as perithecia in fallen leaves. The principal inoculum (which functions in direct infection of expanding leaves) is conidia produced in acervuli on twigs and stems. A second, less significant source of primary inoculum is ascospores produced in perithecia. Mycelium, overwintering in stems, may infect developing buds. Conidia are disseminated by wind and splashing rain. The fungus penetrates leaf or succulent stem surfaces via the production of appressoria or through wounds. Growth of the anthracnose fungus in infected tissues results in a number of primarily necrotic symptoms.
Management recommendations include:
1. Exclusing of the pathogen by planting disease-free seedlings/cuttings.
2. Eradicating the pathogen by cutting and burning infected trees during harvesting operations.
3. Pruning and burning infected plant parts (urban settings).
4. Planting genetically resistant/tolerant selections.
Vernon Ammon, Ph.D., Professor and Plant
Pathologist
Mukund V. Patel, Extension Plant Pathologist
The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended of other products that may also be suitable and that these products have maintained label clearance.