Some common problems with lemon trees are pest damage, citrus cankers, anthracnose and sooty mold fungus. Treatments are available for some of these problems, while the destruction of the lemon tree is necessary when other problems arise.
A bacterial infection which causes yellow lesions on the fruits and leaves of the lemon trees causes citrus cankers. Liquid copper fungicide prevents the condition, but if the tree is already infected, destroying it is the only solution.
Long periods of rain cause anthracnose, a fungal infection that results in stained fruit. Sooty mold fungus results in black leaves, and liquid copper fungicide also treats it.