Hackberry mess

[Perry]

I have two hackberry trees in my front yard. This time of year, anything under the hackberry trees are covered in a filthy black stain. Question #1...What *is* the black stuff?. Question #2....is there anything to do to overcome the black stuff? such as a certain food or fertilizer additive. It's awful. I am in the Deep South, southwest of New Orleans. It looks like mildew....but I don't think that's what it is. Perry

[Colbyt]

IMHO it is rotten berries and bird poo from where they came to eat the berries.

My solution was to cut down the trees.