Juniper: Rust

Biology

Several types of rusts infect junipers. The alternate hosts for most of the rusts are in the rose family, including plants such as hawthorn, cotoneaster, and apple. Infected junipers develop round or elongate galls on the branches. The galls may be greenish-brown, tan, or reddish in color. Twigs above the galls may die back or may form witches’ brooms. In the spring, the galls typically produce reddish fungal fruiting bodies which may appear slimy or gelatinous when wet. The fungus produces spores on the alternate hosts in mid to late summer. Pear trellis rust is also found on ornamental junipers.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• Avoid overhead watering. Moisture is necessary for infection to occur.
• Remove infected leaves on alternate host plants such as apple or hawthorn, or remove suspected alternate hosts in the vicinity of the junipers.
• Prune and destroy galls in junipers before the fruiting period in the spring.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• None recommended