Another stately tree with enormous value to our hardwood forests especially lowlands is struggling in the urban forest. Tree-lined streets of 80+ year old sycamores are slowing and visibly dying. Why? Let’s first learn a bit more about this giant of the Eastern forests of the US.
The tree can grow to heights of 60 – 120 feet on a trunk girth of three to eight feet (diameter at breast height or four feet from the ground). This tree can live to be 250 years old. It’s a favorite nesting tree for owls and chimney swifts if canopy cavities permit, as well as purple finch, goldfinch, chickadees and other common urban birds eating the seeds. Due to its fast growth rate the tree has been explored for reclaiming/remediating soils poisoned by heavy metals.
As far as ecosystem services provided by this tree they are the one mentioned above plus a tremendous amount of shade. Birders will tell you it is one of the best canopies to explore in the early spring for the Cerulean Warbler (endangered) which tends to perch high atop and sing for a mate at that time of year. I couldn’t find data on its average carbon sequestration per lifetime but anything that can produce wood (which is essentially massively long chains of carbon) at up to two feet per year and live a couple hundred years with a trunk reaching 100+ feet tall, well, that has got to be an excellent way to store carbon from the atmosphere (sequestering it in bark and trunk and roots). Those sail-like leaves sometimes the size of an adult hand must collect a good amount of particulate matter. All of those characteristics result in cleaner air, healthier soils, and cleaner water. That’s quite a lot of services for, I don’t know, a $30 tree someone bought 50+ years ago. Okay, I’m coming down off the soapbox.
So why are they dying. Well, it’s not a new disease but was first reported in the 1950s (citation). The symptoms are a dark discoloration of the mid and primary veins spreading outward canopy thinning, frequent and reoccurring leaf fall especially in the early spring, and can be accompanied by increased wood boring activity by beetles and termites. The latter is due to the decreased wood strength from a weakened production of healthy cells including woody tissues. The disease I am seeing hitting creek-bed and city streets hard is the Sycamore anthracnose. It’s damage is most notable in the early spring and then again the Summer. The tree will seem to bounce back in springs that are dry and cool. Once the temps heat up or humidity rises – the anthracnose strain will present itself again.
It can be readily treated with a systemic that not only provides five years of protection in mature trees, but also is applied in a manner with the least possible exposure to humans, pollinators, and pets. The yeast used by bee larvae as a major protein source is in the nectar their bee ‘parents’ bring back to the larvae and if that nectar is exposed to topical fungicides the yeast dies. So, proper fungicide applications to protect beneficial microbes is key to good plant/tree health care.