• Lemon plants are small evergreen trees.lemons and lemon tree image by jc from Fotolia.com
  
  Lemon plants are small evergreen trees that can be grown indoors as houseplants or outside in warmer climates. They can suffer from common diseases that also affect the roots, leaves and branches of other citrus plants, such as orange and lime. Annual pruning can help stop the spread of diseases and should be carried out before the lemon plant blooms. When pruning, remove any dead, diseased or broken branches by cutting just above the collar with some pruning clippers or lopping shears. The collar is the swollen part of the branch near the trunk. Also remove branches that are rubbing against each other as they can create open wounds that also spread disease.
  
  

Greasy Rot

• This appears as yellow-brown, black or brown spots on foliage and looks similar to small blisters. The spots appear two to nine months after infection, followed by the lemon plant shedding its leaves.
  
  

Citrus Canker

• Lesions forming on the fruits, stems and leaves of a lemon plant are a sign that it has been affected by citrus canker. The disease can cause the lemon to shed its leaves and drop its fruit early, and it sometimes leads to the death of the specimen.
  
  

Root Rot

• If the lemon plant has yellow leaves and is shedding its foliage, this is a sign of root rot. This disease is caused by waterlogged soil or by leaving the plant to stand in water if it has been kept as a houseplant.