Pear trellis rust is easily identified by the rust-coloured spots that develop on the pear tree's leaves in early summer. The spots grow larger as the season progresses. By fall, the pear tree will lose many of its leaves. And the spots (on remaining or fallen leaves) develop grey, trellis-like hairy growths which are the fungus' spores. These are easily airborne and will almost certainly infect any pear (or juniper) trees within 100 feet of the host. The best way to get rid of rust on pear fruit trees is to prune away infected tissue. There are no fungicides scheduled for use on pear trellis rust.
Prune any leaves that develop rust-coloured spots. To prevent the spread of the fungus, these leaves must be pruned before mid-August when the fungus' spores begin to develop.
Prune any twigs that develop galls at their bases, a symptom of a severely affected tree.
Gather all pruned material immediately, place it in a plastic bag and throw it away. Do not compost infected plant material. The fungus will still develop even after it is removed from the tree.
Pear trellis fungus is highly contagious. If the pear tree is not pruned soon enough, the infection will spread to nearby trees. Many horticulturalists recommend culling severely infected pear trees to save the neighbouring crop, especially if unaffected juniper or pear trees are cultivated within 100 feet to 1/2 mile of the affected tree.