Student Project Environmental influences on box blight epidemics

Abstract

Calonectria pseudonaviculata and C. henricotiae are two recently differentiated fungal species responsible for box blight, a disease that threatens the Buxus genus. Infection can be introduced to gardens on new plants and is spread through the use of tools. The fungus survives on stem lesions and fallen leaves when spores are dispersed by rainsplash. In this study, 195 Calonectria UK isolates collected by the Royal Horticultural Society (RHS) Advisory Service were identified to species level. Detached stem assays were performed to assess how long stem and leaf lesions remain infectious, and their sensitivity to fungicides. A survey was also carried out at three National Trust properties on the effect of clipping on box blight distribution and severity. It was found that C. henricotiae was only present in and after 2011. C. henricotiae is more thermotolerant, and the increase in prevalence may be a result of increasing temperature and longer dry spells in the UK. Sporulation could occur multiple times on both stem and leaf lesions in humid conditions, although spore production dropped markedly after six sporulation events. Fungicides were effective at preventing spore production on stem lesions. Long dry spells may also reduce Calonectria’s ability to sporulate, leading to limited box blight spread between plants.