Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2016
Publication Date: 10/5/2016
Citation: Shishkoff, N. 2016. Survival of Calonectria pseudonaviculata in leaves, twigs, and discrete microsclerotia in sand at two moisture levels and five temperatures. Plant Disease. 100:2018-2024. https://doi.org/10.1094/PDIS-09-15-1098-RE.
Interpretive Summary: Boxwood blight is caused by Calonectria pseudonaviculata in the US, where the disease appeared in 2011 and is currently reported from 18 states. The disease worries the boxwood nursery industry, whose yearly wholesale market value is estimated at $103 million. In this study, when infected boxwood tissue was incubated in sand at two moisture levels and at 5 temperatures, sporulation from tissue samples declined to zero after five months at 30 C while sporulation at -10 C ceased by 7 months. At 0, 10, and 20 C, sporulation continued through the 30 months sampled. For discrete microsclerotia grown on cellophane sheets and sampled over time, sporulation did not occur after 2 months at 30 C, or after 7 months at -10 C. At all other temperatures sporulation continued over the 30 months sampled. This suggests that extremes of hot and cold will kill the pathogen in litter but at moderate temperatures it will remain in soil for long periods, making replanting in affected sites difficult.
Technical Abstract: When leaves or twigs of boxwood infected with Calonectria pseudonaviculata were incubated in sand at two moisture levels (carrying capacity at 36% water v:v and sand at 5% water v:v) and at 5 temperatures (-10, 0, 10, 20, and 30 C), sporulation from monthly tissue samples plated on GYET media declined to zero after five months at 30 C and after 7 months at -10 C. At 0, 10, and 20 C, sporulation continued through 30 months. Statistical analysis through 16 months showed a significant effect for temperature in all sample types. For discrete microsclerotia grown on cellophane sheets, sporulation did not occur after 2 months at 30 C, or after7 months at -10 C. At all other temperatures they continued to germinate over the 30 months sampled. Statistical analysis through 16 months showed significant effects for temperature and moisture level.