Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2016
Publication Date: 1/14/2016
Citation: Shishkoff, N. 2016. Survival of microsclerotia of Calonectria pseudonaviculata and C. henricotiae exposed to sanitizers. Plant Health Progress. 17:13-17. doi:10.1094/PHP-RS-15-0038.
Interpretive Summary: Boxwood blight is caused by two fungi: Calonectria pseudonaviculata and C. henricotiae. The disease was first seen in Britain and New Zealand in the 1990s, spreading throughout Europe thereafter. In the US, the disease appeared in 2011 and is currently reported from 18 states. The pathogen was named C. pseudonaviculata, but some populations differed enough to be considered a new species, C. henricotiae. So far only C. pseudonaviculata is known in the US. The disease worries the boxwood industry, whose yearly wholesale market value is estimated at $103 million, not only because it can kill or disfigure boxwood, but because infested litter contains fungal structures called microsclerotia that persist in soil for long periods, making replanting boxwood in affected sites difficult. In this study, microsclerotia of C. pseudonaviculata were treated with eight commercially available sanitizers to discover effective methods to clean up nurseries. Ethanol (70%) proved most effective, killing microsclerotia in less than 5 min. The most effective sanitizers were then used in tests of microsclerotia of both species, where those of C. henricotiae were found to be more sensitive regardless of size. Since other research has found differences in fungicide sensitivity and thermotolerance between the two species, the findings suggest that the species should be considered as separate threats to boxwood and their differences elucidated.
Technical Abstract: Persistent resting structures (microsclerotia) of Calonectria pseudonaviculata (causal agent of boxwood blight disease) were treated with eight commercially available sanitizers (Zerotol 2.0, Oxidate, Sanidate, X3, Greenshield and Lysol Concentrate at maximum label rates, plus 70% ethanol and 0.6% sodium hypochlorite) to discover effective methods of disinfestation of nursery beds and benches. Ethanol proved most effective, killing microsclerotia in less than 5 min. Zerotol, 10% bleach, and 70% ethanol were used in comparison tests of microsclerotia of C. pseudonaviculata and C. henricotiae (a second species of blight pathogen not yet found in the US) where microsclerotia of C. henricotiae were found to be more sensitive regardless of size.