P&PDL Picture of the Week for
May 25, 2009

Anthracnose of Shade Trees

Gail Ruhl, Plant Disease Diagnostician, Department of Botany & Plant Pathology, Purdue University

Anthracnose is the common name for a type of leaf spot and canker disease caused by certain kinds of fungi. Anthracnose diseases affect many trees, but are particularly prevalent on ash, maple, sycamore, white oak, walnut and dogwood. Each species of tree is infected by a different species of fungus, thus the fungus does not spread from oak to maple or maple to ash or ash to sycamore. A different fungal species is also responsible for dogwood anthracnose.

Symptoms are especially severe in years with cool, wet spring weather. The symptoms will vary depending on the type of tree and the stage of plant development at the time of infection: leaf spots or blotches; twig dieback and wilting; and browning or death of emerging leaves are all possible. Premature leaf drop often occurs with anthracnose diseases, however, most of the trees infected with anthracnose usually show good resilience, and are not permanently damaged by this early season leaf blight.

Sycamore anthracnose causes severe blighting of newly emerging leaves and shoots. Twig and branch cankers, shoot blight, and leaf blight are all symptoms of the fungus that causes sycamore anthracnose. Leaflet drop, as well as dead tissue along leaf veins or at the leaf edges is a symptom for ash anthracnose. Although defoliation may be so great that anthracnose-infected leaflets practically carpet the walks and lawns nearby, the tree is not dying, it simply puts out a new set of leaves. Anthracnose symptoms on maple and oak range from leaf spots to enlarged blighted dead areas along veins and sometimes to shoot blight.

Anthracnose infected trees need to grow more actively than they Normally would in mid-summer to replace lost leaves. Thus cultural practices That include maintaining a balanced fertilization program and watering During drought stress periods are important for the active growth required in the current season and for the regeneration of carbohydrate reserves In preparation for the dormant season. For additional management suggestions for anthracnose and other leaf spot diseases please refer to the following Purdue publications:

Anthracnose of Shade Trees - BP-9-W (pdf file)

Dogwood Anthracnose BP-48

Leaf Diseases BP-143-W (pdf file)

Click image to enlarge

Ash Anthracnose

Maple Anthracnose

Sycamore Anthracnose

Oak Anthracnose

Dogwood Anthracnose (Discula destructiva)

Dogwood Spot Anthracnose (Elsinoe corni)

 

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service