Pine – Fusiform Rust
Q: My wife noticed this on one of our pine trees. Do you have any idea what it is and how to treat it?
A: The knots and orange powder are signs of fusiform rust disease. The orange spores will be blown by the wind to nearby oak tree leaves, where they will mature for a year. The developed spores infect young pine shoots or wounds on a limb or trunk.
There are no fungicides available to treat fusiform rust. Your best course of action is to remove the infected limbs.
Orange powder coming from the trunk of a pine tree indicates an infection there. The trunk will be weakened at that point and the whole tree will need to be removed in the future.