Answer: Tulip tree is susceptible to aphids, which cause sooty mold, and scale insects. It's difficult to control the aphids on such a large tree but insecticidal soap will work against them. As the aphids feed, they excrete a sticky substance called honeydew which turns into sooty mold. Neither will kill the tree but both look unattractive. Scale insects can be controlled with horticultural oil sprays. There are no systemics registered for this tree that would keep theses pests at bay. Wish I had better news for you.
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