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How to Control Cedar Apple Rust

By G.K. Bayne ; Updated September 21, 2017
Cedar trees along fence row, note small brown galls on limbs.
Alaska range image by MAXFX from Fotolia.com

Cedar apple rust is a fungus that infects apple trees. The rust can defoliate leaves and cover the fruit, making it unmarketable. The fungus is transferred from the eastern red cedar tree. The fungus spore is carried on the wind or through birds from cedar trees that can be located miles away from the apple orchard. While elimination of the cedar tree will aid in reducing the rust on the apple, it may not be feasible. The best method of control is selecting varieties of apples that are rust resistant and spraying.

Locate all eastern red cedar trees that are in close proximity to the apple orchard. Use the chain saw to remove the trees at ground level. While complete elimination may not be possible, removing as much of the fungal source will aid in reducing the transference of the spore to the apple tree.

Consult the local agricultural extension service for a recommended fungicide and an accurate spraying schedule. Apple trees are most susceptible when the temperature range is between 46 degrees F and 75 degrees F. The leaves are vulnerable when they have an age between four days to eight days after emerging. The fruit of the apple tree can be infected when in tight cluster, pink buds, to a full-blooming flower.

Mix the fungicide chemical according to the manufacturer's instructions.

Pour the mixture into the sprayer. Cover the tree’s limbs and lower trunk section with the fungicide. You may wish to spray the ground under the tree if the limbs are close to the soil.

Repeat spraying the apple tree according to the extension service schedule. Typically, spraying can cease once the leaves are of a certain age and the size of the apple is larger than 3/4 of an inch in diameter.


Things You Will Need

  • Chain saw
  • Fungicide chemical
  • Sprayer


  • Consult your local agricultural extension agent for sprays that are recommended for your area. Various fungal spores may be different for areas around the country.
  • Cedar apple rust affects apple trees east of the Rocky Mountain range. This is due to the fact that the eastern red cedar will not extend its growth to areas west of the Rockies.