Pear Trellis & Rust Disease

Life Cycle

• While all pears are susceptible to pear trellis rust, not all juniper species are. Those that are not immune act as the pathogen’s host over the winter. Bumps or swellings on the twigs are an indication that the pathogen has taken up residence on the juniper. When the weather begins to warm up, and rain or humidity is present, spores begin forming. The wind picks up the spores and deposits them on the pear tree, which then becomes infected.

Symptoms

• Pear trellis rust initially shows up as a yellow to orange spot on both sides of the tree’s foliage. These spots soon turn red and, by early summer, the spots grow larger and turn a brighter red and orange. By the end of the summer, white growths form on the underside of the leaves and on the fruit, which may dry up and harden. If the disease isn’t controlled, the tree may lose all of its leaves.

Control

• There is currently no chemical control labeled for use on the pear tree for this disease. Cultural control involves removing and burning the galls from nearby junipers. Prune out infected parts of the pear tree and remove mummified fruit from the branches and the soil beneath the tree. Removal of one of the host trees – either the pear or the juniper – is the only way to completely control the disease.

Prevention

• Keep a distance of at least 1,000 feet between junipers and pear trees to prevent them from infecting one another. Inspect the juniper in mid-spring for galls on the branches and shoots and remove them as soon as you see them. Fungicides that contain a combination of pyraclostrogin and boscalid as active ingredients prevent pear trellis rust on ornamental pears.