Why Is My Elm Tree Dying?

Are the leaves browning on the branches?

Did the browning started at the lower branches and is affecting only a part of the tree?

Are there any small, winged insects on your elm tree?

Are there any small, dark brown to black beetles visible in late spring to early summer?

Dutch elm disease usually starts on lower branches, and may appear random, affecting only part of the tree and leaving another part unscathed. The disease is caused by a fungus spread by elm bark beetles. There is no cure for Dutch elm disease but the tree may respond if prune off all affected branches. This is a treatment that extends the life of the tree for several years if caught early and done properly.

Elm phloem necrosis or Elm yellows is a disease that affects the entire crown at once. Elm phloem necrosis is spread by white-banded leafhoppers. There is no cure for elm phloem disease. Infected trees should be taken down as soon as possible.

Several leafhopper species spread elm yellows disease, but the white-banded leafhopper (Scaphoideus luteolus) is by far the worst culprit. These small, winged insects feed on infected elm phloem, picking up the pathogens when they suck out the fluids. The disease organisms incubate inside of a leafhopper for about three weeks before moving into the insect's salivary glands.

Two different beetle bark species transfer Dutch elm disease pathogens among trees: the native elm bark beetle (Hylurgopinus rufipes) and the European elm bark beetle (Scolytus mutistriatus). Adult females of both species dig tiny egg galleries in dead and dying wood. The larvae overwinter in the galleries, emerging as small, dark brown to black adult beetles in late spring to early summer. Newly emerged beetles fly a short distance to find new feeding sites, carrying the fungal spores with them and infecting healthy elm trees.

Elms prefer full sun or partial shade and moist, well-drained fertile soil. They adapt to wet or dry soil as well. They make good street trees because they tolerate urban conditions, but keep in mind than planting an elm tree near sidewalks can lead to cracks and raised areas.