• Apple trees have several leaf diseases.apple image by Serguei Liachenko from Fotolia.com
  
  Several different diseases attack apple leaves. Although most of these diseases are harmless in their mild forms, they can pose a danger to the tree or fruit when severe infections exist. The best way to prevent leaf diseases is to take a proactive approach to apple management. A healthy tree is better suited to resisting disease and is the best way to avoid unwanted problems.
  
  

Apple Scab

• Apple scab is a type of apple disease that attacks the leaves and fruit of the tree. First the spots appear as olive green. In a few weeks the spots appear as if a scab has formed over the area. Scab is only a problem when it is severe enough to cause the leaves to drop off. Infection is less likely in drier climates. A fungicide is the best way to control scab, along with removal of infected leaves.
  
  

Cedar Apple Rust

• Cedar apple rust attacks the leaves of apple trees. Small, yellow or orange spots appear on the bottom of leaves, giving the appearance that the leaves are rusting. Little nubs on the bottom of the leaves release spores which distribute the rust. Eliminate the disease by removing the spore nodes and use a sulfur fungicide to destroy the rust before it can spread to other leaves and trees.
  
  

Fire Blight

• Fire blight causes apple leaves to shrivel, curl and turn black as if they were set on fire at some point. Fire blight is caused by bacteria that harbors inside cankers or cut areas of the tree during the winter. In the spring, the blight emerges, damaging the tree. A fire blight infection is rapid, and immediate care is necessary to prevent the destruction of the tree. Remove infected areas immediately and burn. Sanitize removal tools with bleach to prevent the spread of the blight. Spray the tree with streptomycin every four to five days during the blossoming period.
  
  

Powdery Mildew

• Powdery mildew is a fungal disease that attacks the leaves of apple trees. The leaves start to look like they have been dusted with a powdery substance. Spores carry this disease through the wind. The disease winters on fallen leaves and damp areas of ground. The best way to prevent this disease is to gather fallen leaves in the fall. During infection, spray apple trees with a fungicide to remove the problem.
  
  

Frogeye Leaf Spot

• Frogeye leaf spot is a disease that creates brown circles on the leaves with a reddish outline, similar to a frog’s eye. Leaf spot is caused by a fungal infection. The disease is controlled with a fungicide. Remove infected leaves when possible.