A Tale of Two Fungi – Leaf blight on Pachysandra

Karen Rane, NPDN National Data Committee
 
The NPDN National Data Committee reviews and edits pest names in the dictionaries associated with the National Data Repository to make sure we are using the most current and correct names for the pests we report.
We occasionally find errors in the listings, such as incorrect synonym names, and we correct them when they are discovered. We’d like to bring your attention to one such correction, involving a common fungal disease found on ground cover plant pachysandra (Pachysandra terminalis).

Did you know there are two fungi reported to cause leaf blight of pachysandra? Volutella pachysandrae was described in the early 20^th century as an opportunistic pathogen on P. terminalis. However, as described by Yang et al in the publication entitled “A Diagnostic Guide for Volutella Blight Affecting Buxaceae” (Plant Health Progress, 2021, Vol 22:578-590), V. pachysandrae has not been found in the US since the 1970’s.

Instead, the fungus that currently causes leaf and stem blight (sometimes called Volutella blight) on pachysandra is actually Coccinonectria pachysandricola (anamorph Volutella pachysandricola). The original entries for Volutella species on pachysandra in the NDR Pest Dictionary had incorrect synonyms assigned to them, adding to the confusion in reporting this disease. The entries have now been corrected.

Because both V. pachysandrae and C. pachysandricola (ana. V. pachysandricola) are legitimately published names, both are retained in the Pest Dictionary. The two fungi can be easily distinguished by the size of the conidia – C. pachysandricola conidia measure 14-20 um, while V. pachysandrae conidia are much smaller (2-6 um) (Yang et al, 2021). We’re asking diagnosticians to make sure they choose Coccinonectria pachysandricola as the pathogen causing leaf and stem blight on pachysandra when uploading records of this disease into the National Repository (unless the conidia measurements match V. pachysandrae).


Leaf blight of pachysandra caused by Coccinonectria pachysandricola.
Photos: D. Clement, Univ. of Maryland.


Leaf blight on pachysandra, caused by Coccinonectria pachysandricola.
Photo: D. Clement, University of Maryland.