DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY
Flowering stem of Mexican sunflower, Tithonia rotundifolia, infected by grey mould, Botrytis cinerea. The picture shows a flower bud that has failed to open due to an infection of grey mould that has caused the (hollow) flower stalk to collapse. The bracts of the flower are entirely covered by fungal mycelium producing spores (grey/brown, mealy appearance), as is the upper part of the stem. B. cinerea is the anamorph (non-sexual) stage of the widespread and common pathogenic fungus, Botryotinia fuckeliana. It reproduces by asexual spores called conidia, the grey-brown powder visible in this picture. It is a serious pest of many plants, including crops such as strawberries, raspberries, tomatoes and courgettes, and occurs mainly in damp conditions in summer and autumn. T. rotundifolia is a late flowering annual from Mexico, particularly suspectible to grey mould in damp autumn weather.
Model release not required. Property release not required.