Insects

• Aphids can appear on your live oak in the spring. They feed on new growth and cause affected leaves to curl. Aphids also produce honey dew, which can encourage the growth of fungus. The tent caterpillar also feeds on the leaves, causing extensive leave drop. Scale insects have also been known to infect live oak trees. If left untreated, these insects can seriously damage your tree. At the first sign of infection, treat with an insecticidal soap or a insecticide.
  
  

Oak Root Fungus

• This disease comes from fungus and mold resulting from over-watering or shallow water tables. The live oak tree's natural conditions are warm summers, and this disease is more common in irrigated landscapes. When the roots are infected, the trunk stops growing and a flat side appears on the trunk of the tree. This fungus can cause the leaves to fall or in extreme infection, the entire canopy of the tree can turn brown. The top of the tree may lose its leaves, or the entire canopy thins. Use fungicides to eliminate this fungus, but with severe infections, it may be necessary to remove the tree.
  
  

Powdery Mildew

• This condition is more common in humid locations such as along the coastline. Powdery mildew affects new growth on the tree and cause malformed twigs that splinter. Leaves appear white or yellow and are malformed. Frequent irrigation increases the likeliness of powdery mildew infections. This disease can kill your tree. At the first sign of infection, treat your tree with a fungicide.
  
  

Anthracnose

• Anthracnose is a fungal disease common along the coast in the live oaks in southern California. Rainfall activates the Anthracnose spores in dead twigs and begins to affect new leaves, spreading from the lower branches up. Leaves discolor and then fall. Warm, wet weather encourages this disease. It will clear by itself in dry weather but sprays of thiophanate-methyl have been known to retard this disease.
  
  

Mistletoe

• Although a well-known and much loved Christmas tradition, mistletoe is a parasitic plant that feeds on trees such as the live oak. Mistletoe grows high in the canopy of the trees and can cause branches to die. Female mistletoe plants produce white berries which attract birds. The birds eat the berries and subsequently spread the mistletoe to new trees. Although the mistletoe drains nutrients from the tree, it shouldn't kill it. However, if your tree is already infected by a disease or insect infestation, mistletoe could stunt your tree's growth. Mistletoe is difficult to eradicate. Removal of all infected branches as soon as the mistletoe appears is recommended but in larger branches, you can remove the mistletoe by cutting it from the branch and then wrapping the area with heavy black plastic to stop re-growth
  
  

Wood Decay

• Usually caused by a heart rot fungus, wood decay usually starts at the base of the trunk. Although not all mushrooms indicate wood decay, large mushrooms can form around the base of the tree or on the tree trunk. Another indication of wood decay is the presence of the the Ambrosia beetle. Many fungi can cause the wood of the live oak to rot. Treatment with insecticide and fungicide may preserve your tree, but in severe infestations, the live oak tree must be removed to avoid damage to surrounding plants or structures.