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Sirococcus tsugae

Sirococcus tsugae

Shoot blight

 

Why: Sirococcus tsugae is a recently described fungal species which was first reported by Germany in 2014. During the same period, the fungus was also detected in the United Kingdom. Previously, S. tsugae was only known to occur in North America. This new species was described following studies on isolates previously regarded as Sirococcus conigerus. In these studies, three distinct species could be identified: Sirococcus conigerus (sensu stricto, occurring in Europe and North America on various conifers), Sirococcus tsugae (isolates from Cedrus and Tsuga in Western North America), Sirococcus piceicola (isolates from Picea in Canada and Switzerland). These recent taxonomic changes render the geographical distribution, host range, and biology difficult to ascertain. However, the Panel on Phytosanitary Measures considered that this fungus could usefully be added to the EPPO Alert List, even with a minimal amount of data.

Symptoms
Symptoms
Symptoms
Symptoms of Sirococcus tsugae on Cedrus atlantica
All pictures were kindly provided by Dr Thomas Brand (Landwirtschaftskammer Niedersachsen, DE)

Where: the currently known distribution is as follows, but is probably incomplete.
EPPO region: Germany, United Kingdom. In Germany, S.tsugae was first found in June 2014 in Niedersachsen on 2 Cedrus atlantica mature trees (1 in a private garden in Bad Zwischenahn and 1 a public area in Rastede). In the United Kingdom, the fungus was identified in February 2014 on a C. atlantica tree in a private residence. Further surveys detected S. tsugae in 21 other locations in England, Wales and Scotland.
North America: Canada (British Columbia), USA (Alaska, Georgia, Maine, Oregon, Vermont, Washington).

On which plants: Cedrus spp. (C. atlantica, C. deodara) and Tsuga spp. (T. canadensis, T. heterophylla, T. mertensiana). It is reported that S. tsugae appears to be less aggressive on T. canadensis than on T. heterophylla.

Damage: S. tsugae causes shoot tip blight. The disease is characterised by light brown discoloration of needles, followed by dieback of the affected shoots and partial shedding of needles. Blight affects the distal parts of branches, seldom killing more than 4 cm (1.5 inch) of the shoot tip growth. In some cases, it can affect many shoot tips on a single tree. S. tsugae can attack seedlings, saplings and larger ornamental and forest trees. On seedlings, blighting may render them unmarketable or cause mortality. Primary infection is believed to occur in the spring, probably shortly after new shoot growth starts.

Symptoms
Symptoms of Sirococcus tsugae on Cedrus atlantica
All pictures were kindly provided by Dr Thomas Brand (Landwirtschaftskammer Niedersachsen, DE)

Dissemination: conidia of the fungus are dispersed by rain splashes and it is probable that strong winds can also disperse them over longer distances. Seed transmission has been reported for S. conigerus, but there is no information about possible seed transmission for S. tsugae.

Pathway: plants for planting, cut foliage? seeds? of Cedrus and Tsuga spp. from countries where S. tsugae occurs.

Possible risks: Cedrus and Tsuga species are valuable ornamental trees in the EPPO region, planted for forestry purposes in some countries. Currently, there are no known effective control measures in North America against S. tsugae in forest stands, and information is scarce about possible control methods in nurseries or in parks and gardens (mainly hygiene methods). Although, much incertainty remains concerning the geographical distribution of S. tsugae its biology and its potential impact in the EPPO region, it cannot be excluded that S. tsugae might cause damage to valuable ornamental trees in the public and private gardens and economic losses, in particular for the nursery sector.

Sources
NPPO of Germany (2014-10).
NPPO of the United Kingdom (2015-10).

INTERNET
- DEFRA. Rapid Pest Risk Analysis (PRA) for: Sirococcus tsugae (dated December 2016). https://planthealthportal.defra.gov.uk/assets/pras/2.1-S-tsugae-PRA-v9.pdf
- Forest Research. http://www.forestry.gov.uk/fr/sirococcus
- JKI website. Express PRA on Sirococcus tsugae (in German). http://pflanzengesundheit.jki.bund.de/dokumente/upload/4d8f8_sirococcus-tsugae_pra.pdf
- State of Vermont. Agency of Natural Resources. Forest Insect and Disease conditions in Vermont 2012. http://fpr.vermont.gov/sites/fpr/files/Forest_and_Forestry/Forest_Health/Library/2012conditionsFINAL.pdf
- USDA. Forest Service (2010) Pest Alert. Siroccocus tsugae. Tip blight on Eastern hemlocks. http://na.fs.fed.us/pubs/palerts/tip_blight/tip_blight_lo_res.pdf
Rossmann AY, Castlebury LA, Farr DF, Stanosz GR (2008) Sirococcus conigenus, Sirococcus piceicola sp. nov. and Sirococcus tsugae sp. nov. on conifers: anamorphic fungi in the Gnomoniaceae, Diaporthales. Forest Pathology 38(1), 47-60.
Smith DR, Stanosz GR (2008) PCR primers for identification of Sirococcus conigenus and S. tsugae, and detection of S. conigenus from symptomatic and asymptomatic red pine shoots. Forest Pathology 38(3), 156-168.
Stanosz GR (2012) Sirococcus Shoot Blight. In: USDA Forest Nursery Pests Agricultural Handbook No. 680, 68-70. (available online http://www.rngr.net/publications/forest-nursery-pests/conifer-diseases/sirococcus-shoot-blight/at_download/file)
Stanosz GR, Smith DR, Sullivan JP, Mech AM, Gandhi KJK, Dalusky MJ, Mayfield AE, Fraedrich SW (2013) Expansion in the known geographic distribution and host range of the shoot blight pathogen Sirococcus tsugae. Poster presented at the 24th USDA Interagency Research Forum on Invasive Species (Annapolis, US, 2013-01-08/11), p 95.
Stanosz GR, Smith DR, Sullivan JP, Mech AM, Gandhi KJK, Dalusky MJ, Mayfield AE, Fraedrich SW (2011) Shoot blight caused by Sirococcus tsugae on Eastern hemlock (Tsuga canadensis) in Georgia. Plant Disease 95(5), 612-612.

EPPO RS 2015/076, 2015/193, 2017/061

Panel review date 2017-03
Entry date 2015-04

 

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