Forest Pathology (2012) 42, 397-404

F.S. Peters, C.L. Holweg, D. Rigling and B. Metzler (2012)
Chestnut blight in south-western Germany: multiple introductions of Cryphonectria parasitica and slow hypovirus spread
Forest Pathology 42 (5), 397-404
Abstract: Cryphonectria parasitica was discovered in the sweet chestnut forests of south-western Germany in 1992. Two main areas affected by chestnut blight were discerned, one to the east and one to the west of the Rhine valley. The occurrence of the fungal pathogen with respect to vegetative compatibility (vc) type and hypovirulence was analysed by sampling chestnut blight cankers between 1992 and 2010. Among 368 C. parasitica isolates sampled in south-western Germany, 9 different vc types were found. East of the Rhine valley, EU-2 is the most widespread vc type. In addition, two isolated forest areas infected with C. parasitica of the vc types EU-14 and EU-28 were detected. West of the Rhine valley, C. parasitica of the vc type EU-65 was repeatedly isolated from an infection focus, the spread of which was successfully suppressed for several years by sanitation measures. Since 2003, additional outbreaks of C. parasitica belonging to the vc types EU-2 and EU-5 were detected in the vicinity. Several other vc types (EU-1, EU-12, EU-33 and one vc type incompatible with any of the 74 European testers) were identified on isolated trees mainly in urban areas across the study area and were subsequently eradicated. The spatial and temporal distribution of the different vc types indicates at least nine different introductory events of C. parasitica into south-western Germany. Natural hypovirulence was only found in the infection area in Baden-Württemberg. A total of four hypovirulent isolates of the vc type EU-2 were obtained, one in 1992 and three in recent years. The four hypoviruses were genetically closely related and belonged to the Spanish/German subtype of Cryphonectria hypovirus 1. As the different vc types in south-western Germany occur mostly in spatially separated, single stands, the introduction of hypovirulence as biological control is expected to be effective.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Daniel Rigling, Berthold Metzler

Research topic(s) for pests/diseases/weeds:
surveys/sampling/distribution
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
surveys/distribution/isolation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Cryphonectria parasitica	Chestnut (Castanea)	Germany
Cryphonectria parasitica hypoviruses (antagonist)	Cryphonectria parasitica	Chestnut (Castanea)	Germany