Pear trees often develop a variant of cedar-apple rust simply referred to as cedar rust or hawthorn rust. This rust fungus can damage the fruit of the pear tree, making it cosmetically unappealing and rendering the rusted parts of the fruit inedible. Additionally, the rust attacks the leaves of the tree, which can weaken the plant and leave it vulnerable to other infections. Preventing cedar rust on pear trees will help insure that you have a good crop and a hardy orchard for years to come.
Identify trees that might be threats in the area. Pear rust is part of a group of rusts called juniper-rosaceous rusts. This means that pear rust spends half of its lifecycle on pear trees, and the other half on juniper trees. Identify cedar and juniper trees in the area so that you know if your pear trees are at risk.
Remove infected junipers immediately. Look for large, swollen growths on the branches and stems of the juniper and cedar trees each spring. These trees must be removed to prevent infection. At the very least, remove all galls from the tree using sterile pruning if you want to save the tree itself, but leaving an infected cedar or juniper standing dramatically increases the risk to your pears because it is nearly impossible to find all of the galls on a tree.
Rake all debris out from under the pear trees at the end of every growing season. This will prevent cedar rust from germinating in the plant debris and attacking the tree. Use a rake to clear out the entire area and dispose of the plant material in sealed plastic bags. Do not compost it.
Treat your pear trees with approved, preventative fungicides. You will have to work with a local expert to insure that you are using the appropriate chemicals, since not all cedar rust fungicides are appropriate for fruit trees, nor are all of them legal in all areas of the country.