• Date palms are susceptible to the fungal disease Graphiola leaf spot.Perry Mastrovito/Creatas/Getty Images
  
  Florida has a warm, damp climate that is excellent for the cultivation of tropical plants and vegetables, but these conditions also encourage the growth of fungus. Fungal diseases take resources from the plants that they need to grow, and in severe cases, can damage or kill the plants. If you notice black fungus on your plants, identification is the first step toward solving the problem.
  
  

Black Rot

• Black rot is a fungal disease that affects the sweet potato in Florida. The fungus responsible spreads from the infected root into the sprouts. It first appears as a black lesion near the potato, then spreads up the plant, causing girdling, which in turn causes the leaves to yellow and the sprouts to die. The fungal spots are black, circular and slightly sunken, with short, bristle-like structures close to the center of the lesion. Black rot is controlled by fumigation prior to planting the sweet potatoes and by dipping the potatoes into a seed treatment fungicide before they are planted.
  
  

Black Sooty Mold

• Black sooty mold is a black fungus that appears as a black stain or powdery covering on the leaves and stem of plants. While this black fungus is not itself harmful, it interferes with the plant's ability to absorb light and water. In turn, this leads to slow growth of the plant and an overall reduction of vigor. It grows when the plant is infected with insects such as Florida wax scales, aphids and mealybugs that produce honeydew, which feeds the black sooty mold. Black sooty mold can be wiped from the plant, but it will recur until the insects are gone.
  
  

Graphiola Leaf Spot

• Graphiola leaf spot is a fungal disease that is also called false smut. In Florida, it affects the Canary Island date palm and the date palm. It produces tiny, black-fungal bodies shaped like cups. The effects of this black fungus are primarily cosmetic and only a serious infection will cause nutrient deficiencies in the tree. Graphiola leaf spot is controlled through the removal of the affected leaves and through fungicides.