Chalara fraxinea

Hymenoscyphus fraxineus is the fungus responsible for the disease known as Chalara or ash dieback.  Chalara causes leaf loss, crown dieback and bark lesions in affected trees.  The disease is spread by wind but more likely to be through the movement of diseased ash plants.  A Plant Health Order prohibits all imports and internal movement of ash seeds, plants and trees.

A species-specific molecular testing using (LAMP) using a Genie II machine allows confirmatory testing of chalara disease from foliar, wood and apothecia found on rachis. The kit is has been validated to both EPPO Standard PM 7/98s (EPPO, 2014) and also in-field validation see Table 1 below. The assay can be used in parallel with a COX (cytochrome oxidase gene) assay, which allows for the detection of host plant DNA, which acts as an internal control assay to assist in the interpretation of negative results. Detection can be achieved within 30 minutes from a simple crude extraction performed in a non-laboratory situation.

Table 1 Chalara fraxinea  LAMP assay validation performance characteristics

 

Diagnostic Sensitivity

98%

Diagnostic Specificity

89%