Hi Meredith,

I'm sorry to hear that you have a river birch that is struggling! These are beautiful, but temperamental trees to have in your landscape, since they natively grow beside rivers and streams and most of us don't have that habitat in our yards.

You mentioned that the leaf drop is mostly on one side of the tree. Leaf drop can be caused by several things, but most of those would result in leaves dropping off all over the tree, not just on one side. Do you notice anything unusual about the environment on that side? For example, were plants or trees removed on that side last winter, so that now that side of the river birch gets more direct, hot sunlight? Could one of the stems/trunks have been partially snapped or girdled or had the bark scraped off by deer, so that just that stem is dying back?

You can check the remaining leaves on that tree to look for signs of disease or pest damage. The spiny witch hazel gall aphid is a possibility (see description in this article: https://hgic.clemson.edu/factsheet/river-birch/) but there are not too many other insect pests that affect river birch (it is the most resistant of the birches to the bronze birch borer).  There are a couple of pathogens of river birch, such as those described here: https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/birch/leavesdrop.html.

The lichens are probably incidental. The kind of wood-eating fungi that appear on dead branches are typically black and not-related to lichens. If your healthy river birch also has some lichens on the stems, then I would not think you would need to worry about that at this time. 

I would love to see some photos of the affected tree from each side, so I can see where the die-back is occurring. If you are able to send some pics from a few steps back, perhaps on both sides of the tree, that might be helpful.

Thanks very much,



Meredith,
These pictures make me think of a phenomenon called "birch die back". Here is a description of it from a previous responder:

Birch dieback causes branches, or parts of the branches, to die. It can affect just a cluster of branches or one whole side of a tree. Birch trees have shallow roots, and therein lies the problem. Shallow roots can be damaged by heat. Fallen leaves can protect the roots, so when they are raked up, the roots lose their protection. An early freeze can also kill off branches, as can warm weather in late winter and/or early spring. Light watering or drought conditions will not get enough water to the roots and a poorly drained soil, will not let excess water drain away, causing root damage. This will not only cause dieback, but will leave the tree susceptible to other diseases and bug infections. Preventing dieback is usually accomplished by planting the tree where it will get at least some shade and using an organic mulch. Since your tree is established you should try to shade the roots with mulch.
The leaves look like they are chlorotic. Chlorosis (yellowing) refers to leaves that are light green or yellow--not a healthy, dark green. Often, leaf veins remain dark while the rest of the blade is lighter. Soils that have a high (alkaline) pH level, may cause problems such as nutrient-deficiency chlorosis. You should test your soil pH levels. Birches thrive at 6.5 pH or below. In alkaline soil, minor nutrients are often bound within the soil chemistry, making them unavailable to the tree. Iron or manganese seems to be the most limiting nutrient in a high soil pH.

It should not be too difficult to place some mulch over the root zone of your tree (but not touching the trunk) to help shade the roots. You can keep the plants growing at the base of the tree if you wish, and just mulch around them. It is also a good idea to get a soil test, in order to determine the pH of the soil where the tree is planted. If the soil is alkaline (over 7), then it will be difficult to sustain a river birch in this spot. 

To obtain a soil test, use our soil testing fact sheet at 
https://ohioline.osu.edu/factsheet/hyg-1132. This includes instructions and a list of sites where you can send your sample for testing. If your other river birch is planted in a different part of your yard, you can have the soil there tested separately as well.

I hope these actions help save the remaining stems of your river birch!

Best,

Meredith,
One addendum to my previous response -- make sure that your river birches are safe from mechanical damage from lawn mowers and weed whackers. The bark on birches is especially thin and can easily be damaged, creating an entry point for infection and further stressing trees.

Thank you, this is very helpful. I didn't put new mulch down this year, so this seems like the most likely issue. I'll get that done asap and get a PH test done as well. Thank you!