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Spermogonia, aecia and uredinia absent. Telia amphigenous, on indefinite spots, scattered or confluent, hemispherical, pulvinate, compact, erumpent, dark chestnut-brown. Teliospores oblong to clavate, rounded above, apex not thickened, rounded or attenuate below, 55-90 x 20-35 µm, up to 100 µm long, walls 2.0-2.5 µm thick, brown, upper cell with apical germ pore, lower cell with superior germ pore;pedicels hyaline, persistent, very long, up to 160 µm.

Recoginition

Both sides of the newest leaves of Buxus plants should be inspected for black pustules containing large, thick-walled, two-celled stalked spores. On plants without pustules, the newest leaves should be examined for spots accompanied by a thickening of the leaves.
Similarities to Other Species/Conditions
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No other rust fungi are reported on Buxus species. The asexual fungus Macrophoma candollei [ Dothiorella candollei ] also causes leaf spots on boxwood (Buxus sempervirens). Its small black pycnidia develop on the undersides of leaves, but the disease begins and is more severe on the oldest of the bush’s foliage, rather than on the newest leaves. The pycnidia produce tendrils, often called cirrhi, of single-celled spores (Batdorf, 1995).

Related invasive species

  • Puccinia buxi

Related Farm Practice

  • Data collection
  • Development
  • Attenuation
Impact

P. buxi is an autoecious microcyclic rust, completing its life cycle with two spore forms on one host. It is native to parts of Europe and Asia. An introduction to the USA, is evidence that it can be invasive with respect to other temperate countries, particularly because its hosts in the genus Buxus are often propagated vegetatively and may carry latent infections. Boxwoods have long been popular as ornamentals, therefore the rust’s current absence from North America and temperate regions of the southern hemisphere is puzzling;in the earliest introductions of the host, the pathogen would probably have been ignored or overlooked. Conditions of boxwood cultivation may discourage the rust’s growth and survival.

Has Cabi datasheet ID
45752
Symptons

Black telia develop on indefinite spots on thickened areas of the leaves (Grove, 1913). Smith et al. (1988) report hypertrophy and dieback of new growth caused by this rust.

Hosts

The rust has been reported from Buxus sempervirens (boxwood) and Buxus microphylla (littleleaf boxwood), commonly grown ornamentals, as well as from the Asian species, Buxus sinica (Chinese boxwood), a cold-hardy species from Korea (Batdorf, 1995).

Oss tagged
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