Mulberry Leaf Spot
Mulberry leaf spot is caused by a type of fungi that attacks the leaves of the tree. Fruitless mulberry trees are particularly susceptible to it. Mulberry leaf spot can be identified by the leaves growing somewhat malformed, yellowed, and having black spots. Mulberry leaf spot can be treated with fungicide. Even without treatment, fruitless mulberry trees can normally survive this disease. The important thing to remember is that you will need to clean up and dispose of all the fallen leaves in the fall or winter. The mulberry leaf spot fungi overwinter on the fallen leaves and in the spring, the rain will splash the fungi back onto the tree, which re-infects it for the next year. Removing and destroying the fallen leaves will help prevent this.
Not Enough Water
Fruitless mulberry trees grow rapidly and their root systems can grow to a massive size. What this means is that what may have been enough water one year will not be enough water the next. When the tree does not get enough water, the mulberry gets yellow leaves. A mulberry tree may be particularly prone to this during periods of drought when the leaves will be transpiring water faster than the roots can take it up. The best course of action is too water the tree deeply about once a week. Watering deeply is better for the tree than multiple shallow waterings. A deep watering will get the water down into the root system so that more of the roots will be able to take water up at the same rate as the leaves transpire it.
Cotton Root Rot
Cotton root rot is another fungus that can cause a mulberry to have yellow leaves. Cotton root rot is characterized by yellowing leaves followed by wilting. The leaves will not fall off the plant though. Unfortunately, by the time the symptoms of cotton root rot are seen, the tree has most likely been damaged beyond repair and will most likely die within a year. Calling an arborist to look at the situation is advised due to the fact that cotton root rot will continue to spread in the soil and kill other surrounding plants and trees. Hopefully your mulberry tree will recover from whatever problem is causing the mulberry tree leaves to turn yellow. Fruitless mulberry trees are amazingly resilient and yours should bounce back in no time at all.
