How to Manage Pests
Pests in Gardens and Landscapes
Alternaria rot—Alternaria citri
Alternaria rot is a fungal disease that affects mainly navel oranges and lemons. Fruit infected with
Alternaria change color prematurely. The decay is softer on lemons than on oranges and develops mostly
during storage. On navel oranges, the disease is also called black rot, and results in dark brown to
black, firm spots or areas at the stylar end or in the navel. If you cut the fruit in half, you can see
the rot extending into the core.
Healthy, good-quality fruit are more resistant to Alternaria rot than stressed or damaged fruits, especially
oranges with split navels. Preventing stress by maintaining a good fertilization and irrigation program
can reduce the incidence of splitting and Alternaria rot.
infects the navel of oranges
rot in the core area