How to Manage Pests

Pests in Gardens and Landscapes

Dutch Elm Disease—Ophiostoma (= Ceratocystis) ulmi

Dutch elm disease is a fungal disease. Symptoms usually first appear in only one portion of the canopy, resulting in yellow or wilting foliage. The dead leaves curl and turn brown, but remain on branches. Peeling back bark reveals brown to blackish streaks in the wood, which appear as dark concentric rings when infected branches are cut in cross section.

Identification | Life cycle

Solutions

Maintain tree vigor by providing adequate summer irrigation in areas with summer drought. Prune elms only from late fall through winter to avoid creating fresh wounds that attract disease-spreading elm bark beetles, which fly during the spring and summer. Bury or (where permitted) burn freshly cut elm wood. Alternatively, seal elm logs tightly under clear plastic in the sun through the warm season and for at least 7 months, after which they are no longer suitable for beetle breeding. Plant resistant species to avoid the disease. Remove infested elms or, if in areas where quarantine regulations do not require tree removal, prune out infested branches. Symptoms must be limited to one or a few limbs and at least 10 feet of healthy wood must separate the infected wood from the pruning point on the main trunk.

Brown foliage from Dutch elm disease
Brown foliage from Dutch elm disease

Logs sealed under tarp
Logs sealed under tarp to exclude beetles


Statewide IPM Program, Agriculture and Natural Resources, University of California
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