Hello,

River Birch (Betula nigra), a handsome specimen tree, is usually found in the wild along stream banks and in swampy bottomlands. It will survive drier soils but prefers moist, fertile, acid soil, with a pH of 6.5 or lower. Although it is heat tolerant, it is not drought tolerant so in dry years, may require supplemental water. It will shed interior leaves if the soil is too dry.

It is not affected by many insect or diseases. However, aphids are common on newer succulent growth. Also, too much rain may result in leaf spot. Read more about River Birch here: https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=277830

However, there may be environmental factors that are affecting the trees, such as new construction, or grade changes near the area.

The second picture shows a tree which appears to be planted too deep. That means that I cannot see the crown of the tree above the soil line, it seems to go straight into the soil. The crown is where the tree flares at the root and the flare should be above the ground level. A tree that is planted too deep may suffer from root rot which can cause the decline of the tree. Read about the proper way to plant a tree here: https://www.treesaregood.org/Portals/0/TreesAreGood_New%20Tree%20Planting_0621.pdf

And here: https://www.arborday.org/trees/planting/

If the tree is planted too deep, I suggest that you carefully pull the mulch and soil back from the trunk.

Often trees show the same symptoms when it is too dry or too wet. You can assess the moisture by sticking your finger in the soil up to the knuckle—if the soil is cool and moist, it is fine if not, it needs more water. Most trees in the landscape require 1 inch of water per week. If you discover that the soil is dry, put a hose over the root area at a slow drip a couple of times a week if there is no rain. By placing an empty tuna can in the garden to catch the rain, you can measure the amount of rain the trees receive.

When a tree needs water, it is stressed. Unfortunately, a stressed tree attracts insects which feed on the weakened tree. Dying leaves may be caused by an aphid attack. A healthy tree is able to fight off attacks by insects and disease.

The only way that you can decide on the proper management of the trees is to have them assessed by a certified arborist. Go to: www.treesaregood.org, the website of the International Society of Arboriculture to find an arborist in your area.

Thank you for contacting Ask Extension.