Studies on the pathogenicity of Neoerysiphe galeopsidis on Catalpa, Acanthus and Lamium

RHS project team
Dr Béatrice Henricot
Dr Roger Cook, Plant Pathologist consultant
Start date
29/01/2006 14:28:09
End date
01/01/2015 14:28:14

powdery mildew, pathogenicity, Neoerysiphe, Catalpa, Acanthus, Lamium, Althaea

The problem

After the first finding of catalpa powdery mildew caused by Erysiphe elevata at RHS Garden Wisley in 2002, work done over the next three seasons showed that the disease in England can be caused by at least four species. Neoerysiphe galeopsidis was found in June/July on Catalpa, but became overrun by Erysiphe elevata later in the season.

Unlike the other powdery mildew species, N. galeopsidis is found on a wide range of wild and cultivated plants. It was responsible for serious damage to Acanthus at RHS Garden Wisley in 2005.

Work is needed to determine whether N. galeopsidis from Acanthus can infect Catalpa and vice versa, and whether N. galeopsidis from wild plants, e.g. Lamium, can infect either of these hosts.


It seems likely that N. galeopsidis has recently broadened its host range in certain parts of the world. To confirm, the following experiments are planned:

  • Test an isolate of N. galeopsidis ex Catalpa to confirm it can infect Acanthus and vice versa.
  • Test an isolate of N. galeopsidis ex Lamium to see if it can infect Catalpa and Acanthus.
  • Test an isolate of N. galeopsidis ex Acanthus to see if it can infect other hosts of this mildew mentioned in the literature such as Althaea and Crassula.
  • Test isolates of N. galeopsidis ex Acanthus from several areas to see if they have a similar host range.
  • Test the pathogenicity of N. galeopsidis and E. elevata, to other Catalpa species.
Benefits to gardeners

The project will provide information about the host range of Neoerysiphe galeopsidis, which can be applied for the management of the disease.

Advisory information

More on powdery mildew


Cook R T A, Henricot B, Henrici A and Beales P (2006) Morphological and phylogenetic comparisons amongst powdery mildews on Catalpa in UK. Mycological Research 110, 672-685.

Cook R TA, Henricot B and Beales P (2006). First report of Neoerysiphe galeopsidis on Acanthus spinosis in the UK. Plant Pathology 55, 575
Read the report

Cook R T A, Henricot B and Kiss L (2004). First record of Erysiphe elevata on Catalpa bignonioides in the UK. Plant Pathology 53, 807.
Read the report

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