KENNEWICK -- Longtime readers of this column know that sycamores are not my favorite tree.
One reason for this forthright antipathy is that the sycamores planted here many years ago are prone to a fungus disease called sycamore anthracnose, aka sycamore blight.
Our last severe outbreak of this disease was in 2006. A quick tour of the older areas of the Tri-Cities reveals that the disease has hit the sycamores hard again this year.
This is no surprise considering the weather this spring. We had the "perfect" conditions for the disease to develop: cool (below 55 degrees), wet weather as the buds first begin to open.
Under these conditions, buds, shoots and newly expanding leaves easily become infected from the spores produced by cankers. These cankers, distinct lesions, found on branches and twigs come from infections that occurred in previous years.
If the disease attacks early in the season, buds and shoots will be killed before they have a chance to develop. Once the leaves have developed, later infections show up as brown-colored dead angular blotches that follow along the veins. These brown areas can expand to include the entire leaf. The fungus also infects twigs and branches, forming cankers that can girdle and kill them. Repeated infections over time result in the tree developing ugly "witches brooms" with clusters of dead twigs at the ends of branches.
What can be done about it? If we know when the next spring with the perfect conditions for infection will occur, there are fungicide sprays that can be applied when the buds swell and again 10 to 14 days later.
Spraying of trees more than 10 feet tall should be handled by a commercial pesticide applicator. This can be an expensive proposition because of the size of these old sycamores and because they need to sprayed twice. As an alternative to spraying, trees can be injected with a fungicide. However, this must be done in early fall by a trained and licensed applicator.
Neither spraying or injection will help trees already infected this spring. Both must be done prior to infection. Given the unpredictable nature of the weather, it's a gamble whether or not to use a fungicide for control every year. Let me point out that sycamores in our area seem to survive repeated infections. However, they do look pretty darn ugly in the winter. Sycamores that are almost bare now will develop more leaves as summer goes along.
While gigantic sycamores no longer fit into the typical smaller home landscapes of today, anyone who is considering planting one should look for cultivars that are resistant to the disease.
Don't plant California sycamore (Platanus racemosa) or American sycamore (P. occidentalis), both very susceptible to sycamore anthracnose.
Two resistant London plane tree hybrid (Plantanus x acerifolia) cultivars are "Liberty" and "Columbia." Another cultivar that's moderately resistant is "Bloodgood."
The other characteristics that have me disliking sycamores are the multitude of large leaves requiring removal in the fall, the nasty seed balls and the sheer massive proportions of the tree that make it a target of tree butchers who practice improper pruning (topping).
However, I do find sycamore bark beautiful. The tree sheds plates of older bark, leaving the trunk with a unique gray, green, yellow and white mosaic appearance.
As the weather turns hot, don't be surprised if you see area sycamore losing big and small pieces of bark from the trunk. It's normal and isn't related to the anthracnose problem.
* Marianne C. Ophardt is a horticulturist for the Washington State University Benton County Extension Office.