Cylindrocladium buxicola
A new leaf and twig blight of Buxus

Why: A new blight disease of Buxus species was observed in the 1990s in UK and in New Zealand. The causal agent was identified as a new fungal species Cylindrocladium buxicola. More recently, this disease has been found in other European countries.

Where: In UK, the disease was discovered in a nursery in Hampshire in late 1994. No new records were reported until 1997 when a sudden outbreak of the disease was noticed. Today, the disease is considered as widespread in UK. In New Zealand, the disease was first reported in 1998. Isolates collected from UK and New Zealand were compared, and it was found that they belonged to the same species (C. buxicola) and showed very little variation (suggesting that these derived from one clone). The origin of this new fungus remains unknown, but it is hypothesized that it has been introduced recently to Europe (and then to New Zealand). In autumn 2000, a similar disease of Buxus was observed in private gardens in Belgium, and C. buxicola was identified as the causal agent. Since then, more samples were received from other Belgian sites, nurseries and garden centres, indicating that the disease is spreading.
EPPO region: Belgium (first found in 2000), France, Ireland, Germany (first found in 2004/2005), Netherlands, UK (widespread throughout the country with an increasing incidence).
Oceania: New Zealand.

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On which plants: Buxus sempervirens (especially cv. Suffruticosa), B. microphylla and B. sinica.

Damage: Symptoms of the disease are dark brown spots on the leaves which eventually coalesce to cover the whole leaf, black streaks on the stems and severe defoliation. Black streaks on the stems appear to progress from the bottom to the top of the plants. Apparently, no plant death has been recorded so far. C. buxicola is often found with a second pathogen Pseudonectria rousseliana (anamorph Volutella buxi) causing dieback, but the two diseases also occur independently.

Dissemination: More data is needed on the biology of the fungus. However, if it is similar to other Cylindrocladium species, it may produce resting spores and survive in fallen leaves. These resting spores could be spread by soil, water splashes, animals and gardeners.

Pathway: Plants for planting of Buxus, soil?

Possible risks: Buxus are commonly planted in European gardens (parterres, hedges, topiary work). Data is lacking on possible control methods. Pruning of infected twigs, and destruction of fallen leaves could help to reduce the inoculum. Apparently, no tree death is reported but the disease seriously affects the appearance of Buxus, a plant which is essentially used for ornamental purposes. The introduction of such a new disease could represent a threat to nurseries, parks and gardens.

Source(s)
Brand T (2005) [Occurrence of Cylindrocladium buxicola B. Henricot on boxwood in Northwest-Germany.]. Nachrichtenblatt des Deutschen Pflanzenschutzdienstes 12, 237-240 (in German).
Crepel, C.; Inghelbrecht, S. (2003) First report of blight on Buxus spp. caused by Cylindrocladium buxicola in Belgium. Plant disease, 87(12), p 1539.
EPPO (2007) Panel meeting on Phytosanitary Measures (2007-03-06/09).
Henricot, B.; Culham, A. (2002) Cylindrocladium buxicola, a new species affecting Buxus spp., and its phylogenetic status. Mycologia, 94(6), 980-997.
Henricot, B.; Pérez Sierra, A.; Prior, C. (2000) A new blight disease on Buxus in the UK caused by the fungus Cylindrocladium buxicola. Plant Pathology, 49, p 805.
Henricot B (2006) Box blight rampages onwards. The Plantsman, September, 153-157.
INTERNET
Henricot, B. (2003) Cylindrocladium buxicola, a new fungal species causing blight on Buxus spp. and its phylogenetic status. Poster presented at the 8th International Congress of Plant Pathology, 2003-02-02/07, Christchurch, New Zealand.
http://www.forestresearch.co.nz
Royal Horticultural Society (UK). Research projects: plant pests and diseases.
http://www.rhs.org.uk/research/project_pandd.asp

EPPO RS 2004/123, 2006/204, 2007/045, 2007/107

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