Citrus Canker

• Citrus canker is a serious, fatal and highly contagious bacterial infection. Yellow halolike lesions will appear all over, on the fruit, leaves and twigs. The bacteria is easily spread from one tree to another by the wind, insects, birds, humans and by using the same pruners on multiple trees without sanitizing them. In most cases, infected trees have to be destroyed to stop the spread, but a preventative is available in the form of sprays that contain a liquid copper fungicide.
  
  

Melanose

• Melanose is a fungus that attacks mostly young grapefruits, but other citrus fruit can be affected. It causes a scab on the rind that does not affect the fruit itself. The diseases is worse if the tree is 10 years of age or older. It lives in dead wood, so pruning is a very effective control, as is using a liquid copper fungicide.
  
  

Greasy Spot

• Greasy spot is another fungus. It is harder to spot because it forms yellow/brown blisters on the bottom side of the leaves. It can cause leaf loss and can infect fruit, particularly the grapefruit rind. The disease is spread by spores, so picking up and disposing of any fallen leaves, as long as it is done on a regular basis, can help. Again, spraying with a liquid copper fungicide in June and July and a second time in August or September will help to protect any new growth.
  
  

Sooty Mold

• Sooty mold is also a fungal infection that causes the leaves to turn black. It is caused by the secretions from whiteflies, aphids and mealybugs. The best course of action is to control the insects and to not let the infection get started. Make sure to spray both sides of the leaves and check after 2 weeks to see if it needs to be repeated. If infection does occur, spray with liquid copper fungicide and again check at the 2-week mark.
  
  

Root Rot

• Root rot is causes by a fungus that lives in the soil. Dark brown patches will appear on the trunk of the tree and will start to ooze. As the disease progresses, the bark will dry out, crack and eventually die. It can also cause the fruit to turn brown and decay and the leaves to turn yellow and die back. Remove all of the fallen leaves and prune off all of the lower branches within 2 feet of the ground. Spray with a fungicide as soon as the disease is detected and then again the following spring.