After a dry winter, this spring has been unusually cool and wet, and while the rain was much needed to break the drought we experienced the last few years, this weather pattern has caused an outbreak of sycamore anthracnose. This disease is largely weather dependent, because cold wet weather after leaf emergence increases the severity of the infection. Wet weather spreads the spores around the tree while cold spells retard tree growth, allowing the fungus to set in, and the tree cannot provide the necessary defenses to ward off the infection. Dry winters increase the likelihood of infection because they weaken the trees immune system by causing stress due to lack of water. From our observations of sycamores in the area, it would appear that more trees are affected by anthracnose than not this year. The strain of anthracnose that affects sycamores is the most serious of the anthracnose diseases in Kansas, and is the most problematic disease of sycamore trees. Anthracnose is the name given to a group of fungal pathogens that affect a variety of trees including oak, ash, elm, sycamore, and many others. Each tree is affected by its own specific strain of fungi. Each strain and tree have similar but different signs and symptoms of anthracnose.
Signs of infected trees are shrived young leaves (fig 1), leaf necrosis (dead areas) on older leaves starting at vein but eventually killing the entire leaf (fig 2), and twig die-back (fig 3). Twigs can develop cankers, which are sunken areas of dead tissue (fig 4). These cankers can spread to larger branches, or even the trunk in some cases. During severe infections so much twig and leaf death may occur that the tree is almost leafless until new foliage emerges in mid-summer (fig 5). These symptoms stress/weaken the tree leaving it open to secondary infections such as other diseases or insects, and make it more susceptible to abiotic (nonliving) stressors like temperature extremes, drought, or flood. The tree can decline and eventually die if the anthracnose or secondary infections are serious enough and left untreated.
The first actions to take are cultural practices which you can do. This means, watering your tree during dry winters and cleaning up tree debris like sticks and leaves. By watering your trees on warm days (temperatures above 40F or 4.5C) during dry winters, you are increasing the vigor of the tree and preventing unnecessary stress from lack of water. Raking leaves and sticks in the fall and discarding or destroying them will remove infected components, and prevent the spores from reinfecting the tree.
Wellnitz Tree Care can prune your trees to remove any dead or infected wood that still harbor spores. We can also treat trees with an injectable fungicide which offers three years of protection from sycamore anthracnose. This injection can be used as a preventative measure or as a treatment after the fact. To inject a tree, we excavate the root flares, drill small holes, and insert tubes, which provide the fungicide (fig 6). This is done from mid-June to early fall once the tree has fully leafed. Using an injectable method allows us to treat the tree without fear of chemical drift or chemical washing away in the rain. There is no need to keep you pets and children off the yard after we are done, as everything goes directly into the tree!
If you think your sycamore has anthracnose, or if you would like a preventative treatment give us a call, send us an email, or send us a message on Facebook! If you are thinking about planting a sycamore tree we can help you pick out and properly plant an anthracnose resistant variety, such as a London plane tree (fig 7). We would love to send a Plant Health Care Technician to your property to determine how we can best meet all of your tree care needs.
310 Congress Street, Emporia, KS 66801 • 5709 SW 21st St., Suite 108, Topeka, KS 66604