Control Options for Trees with Sycamore Blight
Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent
Living in Prosser and working in the Tri-Cities, I have often been able to notice a distinct difference in the climates of each area. This spring the disparity between the two has become very evident because of a disease problem showing up on sycamore trees. The sycamores in the Prosser and Grandview area have been hit hard by sycamore anthracnose, also known as sycamore blight. It=s a fungus disease that attacks sycamore buds, shoots, twigs, and leaves.
Our native sycamores, the western sycamore (Plantanus racemosa) and the American plane tree (Plantanus occidentalis), are very susceptible to sycamore anthracnose, a fungus disease common in this region. The Oriental plane tree (Plantanus orientalis) and the original (not seedling offspring) London plane tree (Plantanus acerifolia) are more resistant, but not immune. Resistant cloned cultivars include >Bloodgood=, >Columbia=, and >Liberty=.
This fungus attacks new tissues when they begin to emerge in the spring. Infection is most severe when the weather is wet and cool with temperatures below 55 degrees. Depending on the timing of the infection, the fungus may infect and kill expanding bud, shoot, and leaf tissues before they fully develop or it can attack leaves later after they=ve expanded. On leaves, the fungus creates brown lesions that form along the midrib and main veins of the leaf.
Cultural Control
Cultural control of the disease consists of raking and destroying fallen leaves and twigs along with keeping the tree adequately watered and fertilized. On smaller trees it=s recommended to prune out and destroy infected twigs and branches. Cankers on these infected branches provide spores for future anthracnose infections. However, removal of cankers by pruning is impractical on large, older trees.
Fungicide Applications
Fungicides to prevent infection can be applied, but these are sprayed onto the tree when the buds begin to swell and the bud caps first start to break. They are applied again 10 days after the first spray. Timing and good coverage over the entire tree is critical in getting control... something that=s very difficult with big trees.
Injections for Control
One other control option is available. This is an injection of a systemic fungicide into the tree. This is done by drilling small holes into the trunk or root collar of a tree and injecting the material into the tree. The fungicide is carried through the water-conducting vessels in the wood to the branches and leaves where it will protect against early season infection.
To be effective this is usually done for two consecutive years. Some materials are injected in the fall; other materials require an early spring application. This procedure should be done only by a professional arborist trained in proper injection techniques. Repeated use of this method may lead to eventual significant damage and wood rot because of the holes that are drilled into the trunk.