Insects and Diseases of Trees in the South

by Anonymous

SYCAMORE ANTHRACNOSE

Defoliation of sycamore tree caused by sycamore anthracnose.

Sycamore anthracnose, caused by Gnomonia veneta, is common on American sycamore throughout its range in the eastern United States.

Anthracnose is a disease characterized by distinctive limited lesions on stem, leaf, or fruit, often accompanied by dieback or blight and usually caused by fungi that produce slimy spores that ooze from small cup-shaped fruiting bodies that are visible with a hand lens. This disease has four distinct symptom stages identified as twig blight, bud blight, shoot blight, and leaf blight. Twig blight appears before leaf emergence and kills the tips of small one-year-old twigs. Infection comes initially from leaf litter and twig cankers. The second stage, bud blight, develops during bud expansion in April and early May. Shoot blight, the most frequently observed symptom, causes the sudden dying of expanding shoots and also young leaves. Leaf blight, the final stage, involves the actual infection of expanding or mature leaves. Diseased portions of the leaf involve irregular brown areas adjacent to the midrib and veins which are dotted with diseased spots. Incidence of anthracnose is directly related to the amount of spring rainfall. Shoot blight is severe if the weather for two weeks after leaf emergence is cool and moist. The disease may defoliate trees, which usually put out a new crop of leaves by late spring or summer.

Control of sycamore anthracnose under forest conditions is not economically feasible. Where the disease is prevalent, other species should be favored during thinnings. In shade and ornamental trees, pruning of infected twigs, burning of leaves, and fertilization will reduce the disease impact.

Leaf and twig symptoms.