Q: I have a strange white substance growing on two trees in my backyard. Can you help me identify it and tell whether it is a hazard to the trees?

A: The white stuff is pine rosin (hardened sap) exuding from a wound in the trunk. The damage is caused by a disease known as pitch canker. There’s not much you can do about it at this point: no sprays or injections will help.

The tree may be somewhat weakened at the point of infection so my advice is to hire a certified arborist to assess overall tree health.

For a list of arborists, see Georgia Arborist Association