Sunlight Exposure

• The Chinese evergreen tree prefers to grow in shady environments; when it is grown in full sun exposure, the direct sunlight can cause leaf yellowing. Unfortunately, there is little that can be done about this problem short of creating some shade over the top of the tree of transplanting the tree to a different growing area if it is still young enough to do so.
  
  

Overwatering or Underwatering

• Many tree growers assume yellow leaves are a sign of underwatering or drought stress, and often it is, but ironically overwatering can also cause yellowed leaves in some species of tree such as the Chinese evergreen. To confirm if this is the case will take some experimentation. Back off watering schedule and see if the leaves return to normal colors or if they continue to dry out. If they continue to dry out, increase watering gradually and check the leaves for a return to normal color.
  
  

Bacterial Leaf Spot

• Yellow leaves can also be an early symptom of any of a number of diseases of the Chinese evergreen. Bacterial leaf spot, for instance, a disease caused by the fungus Epipremnum aureum, begins as spots on leaves that are surrounded by conspicuous yellow halos. Treat this disease by pruning away infected parts of the tree and discarding them immediately to prevent the spread of the disease to other, nearby trees. Treat serious infections with an approved insecticide.
  
  

Bacterial Blight

• Bacterial blight affects many different plant species. Yellowing of new leaves is an indication that a tree has been infected by a strain of the disease that acts systemically, damaging the tree from the inside out. Leaves also wilt and defoliate. Another unique symptom of this disease is a mushy area of rot around the tree's stems that takes on an offensive odor. Control methods are the same as those described for bacterial leaf spot.