Phytophthora lateralis: identifying Lawson cypress

Lawson cypress or Leyland cypress?

Brown or bronze foliage may suggest a Phytophthora lateralis infection in Lawson cypress conifers.

Many people find it difficult to distinguish between Lawson cypress (Chamaecyparis lawsoniana) and the similar Leyland cypress (Cupressocyparis leylandii). Both conifer species can develop brown foliage but this may not be a symptom of a P .lateralis infection .

Lawson's cypress tree (Chamaecyparis lawsoniana) infected with Phytophthora lateralis at Balloch Castle Country Park, West Dunbartonshire, ScotlandIn fact, P .lateralis has never been confirmed infecting Leyland cypress. Brown foliage in this species is typically due to cold winter temperatures or aphid attack.

Lawson cypress is typically planted as an ornamental tree. It is an evergreen conifer with flat fern-like foliage, scales rather than needles and small cones that (when present) are about 1cm or less in diameter. Crushed Lawson cypress foliage smells of parsley; a resinous, acrid smell suggests you have a Leyland cypress specimen.

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