Brown Rot on Orange Trees

Physical Description

• Brown rot goes by many names, including root rot and collar rot. It leaves dark-brown hardened patches along a tree's trunk, and these patches often crack and release a sticky ooze. If left untreated, the bark can slowly wither and die. Like many plant diseases, brown rot may begin in one spot and gradually spread until it affects the greater part of the tree.

Causes

• Brown rot most commonly grows in moist condition, sometimes taking form after a severe rainstorm or an extended period of wet weather. Brown rot thrives on persistently wet soil and results from the germination of a fungus of the phytophthora species. This fungus lives on soil, which is why the problem usually begins at the root of the tree. Splashing water causes the soil to rise reach higher elevations on the tree, resulting in faster spread and contamination of oranges.

Dangers

• If left untreated, brown rot can cause oranges to become brown or yellow and decay. Eating infected fruits can cause illness, so avoid them. In some cases, the fungus does the majority of its damage to the orange tree internally, compromising and weakening the structural components. So even if a tree appears to be strong, with only a few external instances of disease, it might be dying on the inside.

Management

• Prune an infected tree to remove all visibly affected branches, fruits and bark. Fully ridding a tree will stop the spread of the disease. Remove all branches within 2 feet of the ground and spray the tree in regular intervals with a fungicide approved for use on orange trees. Read the label to determine exactly how often you should spray the tree. Apply the fungicide liberally wherever you find signs of brown rot.