Magnolia Tree Root Damage

Stressed magnolia trees are more susceptible to diseases, pests and root conditions.

Magnolia trees are ornamental trees that are grown in warm southern regions for the showy flowers they provide. This deciduous, semi-evergreen tree is available in 80 different species, the most common of which are the southern magnolia, star magnolia, and sweetbay magnolia. Although generally healthy, the root system of this tree has been known to be damaged by magnolia root borers, girdling and fungus rot.

Magnolia Root Borer

The magnolia root borer (Euzophera magnolialis) is more common in trees which have become stressed. As this pest attacks the root of the tree, the tree will start to show a decline in health. The pupate form of this insect lives under the bark. The larvae feed on the root system of the magnolia tree, preventing the tree from being able to absorb the necessary nutrients from the soil.

Root Borer Control

Unfortunately, there is no proven solution for control, but some insecticides available at local garden centers have been effective. When applying any insecticide, follow manufacturer instructions carefully.

Root Girdle

Magnolia roots can be damaged simply by their growth habit. As they grow, magnolia roots tend to circle their own trunk or root ball. This happens most commonly at the top of the root ball, where the lowest portion of the trunk is located. If transplanting a magnolia tree, it is important to inspect the root system for any girdling and if this condition is present, cut any of the offending roots prior to planting the tree. The magnolia tree features a root system that is much more extensive than the average tree, making it much easier to transplant container-grown magnolias than field-grown magnolia trees.

Varnish Fungus Rot

Varnish fungus rot (Ganoderma licidum) is a fungal disease that attacks the root system and severely damages the health of the tree. Infected trees feature 14-inch conks that cover the base of the magnolia tree's trunk. As the disease progresses, the health of the tree deteriorates and the conks can extend up the trunk to the 15-foot mark. Just three to five years after initial infection, the life of the tree can be compromised. Because trees which have been stressed due to drought conditions and open wounds are more susceptible, try to maintain healthy trees to make them less likely to contract this fungal disease.

Promote Healthy Growth

Magnolia trees grow well when planted in warm climates in USDA Hardiness Zones 7 through 10. Within these zones, magnolia trees should be planted in acidic or slightly alkaline soils where they receive partial sunlight. To promote healthy root growth, make sure the tree is planted in an area where there is plenty of room and soil for proper root expansion.

References

• University of Florida: Southern Magnolia
• Clemson University: Magnolia
• University of California: Wood Decay Fungi in Landscape Trees
• University of Florida: Southern Magnolia