Sweet Gum Tree Diseases

The American sweet gum tree is also called Liquidambar. It is a popular street tree and is prized for its flashy display of fall foliage. It grows to 75 feet in height and prefers full sun in Zones 5 to 9, which includes all but the very northern and southern parts of the United States. The sweet gum tree grows fairly fast and thrives in different types of soil, including sand and clay. It is one of the 100 most common trees in North America. However, it can be prone to certain diseases, which you, the homeowner, will want to know about.

Planting

Choose an area that is large enough to accommodate a very large tree because this one can become 40 to 45 feet in width and 75 feel tall. The soil in your location must be very deep and well drained. If you live in a dry area, sweet gum might not grow as well as it does in areas that receive moderate amounts of rainfall (20 to 50 inches a year). Purchase your tree from a nursery. Spring is the best time to plant. Be sure to keep it well watered until winter rains take over that task for you, especially if your summers are hot and dry.

Insects

Insects rarely attack the sweet gum tree, but several types of scale insects can affect this type of tree, depending on the location.

Canker and Fungal Diseases

You will know if your sweet gum tree has a canker disease because sunken areas can occur on its trunk, sometimes causing it to weep sap.
Fungal diseases include several types of root rot and blight, depending on the location of the tree in the United States. For example, trees in Texas are susceptible to Phymatotrichum root rot (Texas root rot). Blights might be caused by drought conditions, but little is known about these types of diseases of the sweet gum.
Phytophthora basal rot affects the sweet gum tree and also rhododendrons, certain firs and maples, beeches and dogwoods. This type of rot causes roots to die, which can stunt the tree's growth and cause early fall colors of its leaves.
Wood rot affects many tree species and they include mushroom-like fungi called shelf fungi, which protrude from the sweet gum tree's bark. In severe cases, wood rot can cause a tree to fall over. Be sure to check the trunk for any suspicious growths from time to time.

Disease Control

Canker diseases are bacterial in nature and can kill a sweet gum tree. Although no chemical control exists to combat this type of disease, if you catch the situation when it first occurs, you can cut the cankers from the trunk. Healthy trees are more likely to avoid getting this type of disease, so keep your tree properly watered and be sure to fertilize it regularly.
Basal rot can cause death of the tree if you fail to correct drainage problems, so stop watering your tree if you notice symptoms. Soil fungicides exist, which you can apply according to label instructions.
If you see spotted leaves on your sweet gum tree, don't worry. Just keep raking up the leaves, but destroy them or take them to your landfill instead of using them as mulch around the tree or adding them to your compost pile.
You can help to control wood rot by removing affected branches.

Cautions and Considerations

Although sweet gum is a popular street tree, it has a large root system that often cracks or lifts sidewalks and paved roads. It's wise to plant your tree 8 to 10 feet away from areas such as driveways, which could be negatively affected by this tree's aggressive roots.
The sweet gum is deciduous, meaning it drops its leaves in the fall. Because of its large size, a mature sweet gum can produce very large quantities of leaves, which create a fair amount of work for you to keep cleaned up.
In severe cases of wood rot, consider removing your sweet gum tree to prevent any possible damage to nearby structures should the tree fall.

References

• U.S. Forest Service Fact Sheet
• Arbor Day Foundation Info
• Michigan State University Extension: Disease Info

Resources

• American Phytopathological Society: Fungal Disease Info
• Wood rot info from University of Illinois