Linden trees are deciduous, broadleaf trees that have a full shape and lush foliage. They are often used as accent trees in landscaping and have small, fragrant flowers. Linden trees require little maintenance and are pollution tolerant, but some trees do develop diseases. The best way to help keep your linden tree healthy and happy is to be aware of the signs and symptoms of these infections so that you can react quickly and effectively should your linden tree develop symptoms.
Linden trees that are bothered by scale insects, which ooze a sweet, sticky substance, often develop sooty mold. This black, fungal infection makes the entire tree look dark and can weaken the tree and kill it if the infection is left untreated. Use sterile pruning to remove affected foliage and limbs, disposing of the plant material in large plastic garbage bags or by burning. To eliminate the scale insects, direct a strong stream of water at the tree and wash the entire thing down using the water to remove the bugs. You can also treat the tree with horticultural oils to make it less attractive to these pests.
Linden trees develop cankers, which are swollen, woody bulges, when they contract a bacterial or fungal infection due to an open wound in the tree. Use sterile pruning to remove cankers during cool weather and dispose of the plant material either by burning or by throwing it away in sealed garbage bags. If the cankers have taken over the circumference of a limb, simply remove the entire limb about 5 inches below the canker girdle. Fertilize your tree to help it recover from the "operation."
The first sign of verticillium wilt in a tree is light-colored, dull foliage in the summer. As the disease progresses, it will cause yellowing on the edges of the leaves and ultimately defoliation. If you scrape away the bark, you can see traces of the fungal infection on the wood of the branches, which will be dark, olive-green. While there is no cure for verticillium wilt, if you prune off affected branches and fertilize the tree with a low-nitrogen, high-potassium fertilizer, it may recover. If not, you will ultimately have to remove the plant from the yard to prevent the spread of infection to other plants and trees.