My ornamental pear tree, which I think is a Chanticleer, developed black spots on its leaves last year. The tree is about 25 feet tall. What can I do about this as I don’t want to lose the tree? Also, a few of its leaves didn’t fall off last year. Should I be concerned about this?
Leaf spot diseases can weaken trees by interrupting photosynthesis, which is how plants create their food in order to grow and build strong defense systems. Fortunately most leaf spot diseases affect only a small percentage of the tree’s leaves. As conditions that promote the disease decline, new growth is not affected. However, leaf spot diseases should be taken very seriously if leaf loss is moderate to complete defoliation in two or more years.
Most leaf spot diseases are caused by fungi that overwinter in infected leaf debris. Wind and splashing rain carry fungal spores back up into the tree in the spring. Either water on the leaves or very high humidity for 12-24 hours is typically required to start an infection. Leaf spots mature in 1-2 weeks and produce spores that can spread further to nearby susceptible trees. In years with high humidity or a lot of rain, leaf spot can spread throughout the tree canopy.
Ornamental pears such as the Chanticleer are known to get leaf spot, but are considered only moderately susceptible. I’m attaching a link below to a site with pictures of Fabraea leaf spot, a fungus which is known to infect ornamental pear, so you can identify what you are seeing.
In any case, the control is good sanitation – rake and destroy all fallen leaf debris in the fall, prune out any dead black twig tips, deformed buds and any stunted growth. Do not put this debris in a home composter, but place out with garden waste for city/municipality disposal. Be sure to sterilize your pruning sheers after each cut and before moving on to another plant or tree, to make sure you are not causing any more spread.
If the problem continues, I would suggest calling an arborist in your area to determine if there is more in the way of treatment that can be done in order to save the tree.
As to the leaves that are still on the tree, the Chanticleer pear is known to hang on to its leaves until late autumn, so it’s not surprising or unusual that a few have hung on all winter.