My outside yucca plants have black spots on their leaves. How do I treat them?
How Do I Get Black Spots Off Yucca Plants’ Leaves
Certified GKH Gardening Expert
It sounds like your yucca has a fungus. Treat the plant with fungicide. I like to use neem oil myself as it is safe for people and pets and also will address any pest issues the plant may have. It's also effective against many pests. Here is more information on it: