Rust plagues many flowers and trees besides pear trees. It is a fungal disorder that is spread by spores and is airborne. Rust appears as orange powdery pimples on the undersides of leaves. Each pimple or pustule is laden with millions of microscopic spores. The disease causes poor fruit quality and the top of the leaves to have yellow spots. The disease spreads by wind and splashing water. The spores are activated by rain and moisture or overhead watering.
Rake all the dead leaves around the tree and dispose of them. Rust is airborne and leaf matter can spread the disease even after the leaves hit the ground.
Use pruning shears to cut away infected leaves and stems.
Water the tree at the base of the plant. Overhead spraying by sprinklers can spread the disease through splashing.
Spray the tree with fungicide before the tree blooms containing the chemical DMI: Myclobutanil. Follow the directions on the label before spraying a second application. This chemical has been approved for home landscapes. To be effective all leaves have to be sprayed top and bottom.
Read the directions for any fungicide very carefully. Never spray when pet or animals are near by. Never spray on a windy day.