Spring Sickness Research

'Spring sickness' has been a puzzling disease of cultivated daylilies in gardens in North America and Europe. Its symptoms tend to manifest as active growth begins. The new leaves become distorted, often with 'ragged' edges and holes, as well as yellowing. This affects plant vigour and in severe cases the entire fan can die back. However, identifying the cause has remained difficult - with explanations ranging from fluctuating environmental conditions to damage by bulb mites.

Investigations of 'spring sickness' financially supported by the BHHS and led by Dr. Robert Grant-Downton with plant pathologists Dr. Molly Dewey at the Department of Plant Sciences, Oxford University and Prof. Jan van Kan at Wageningen University have identified a new Botrytis (grey mould) species that appears to be responsible. The work is now published in the journal PLoS One.

his species, now formally described as Botrytis deweyae to honour Dr. Dewey's work on Botrytis, was difficult to identify as it tends not to show easily distinguishable features, such as spores. Its initial identification was made using molecular techniques. This finding is fitting as the spring foliage of various monocotyledons can be affected by specialist Botrytis pathogens such as in tulip fire (caused by Botrytis tulipae) and Narcissus smoulder (caused by Botrytis narcissicola).
A daylily leaf affected by spring sickness
©Robert Grant-Downton
The surface of a culture of Botrytis deweyae showing the production of dark (melanised) resting bodies called sclerotia
©Robert Grant-Downton
A light micrograph of sporulating Botrytis deweyae in pure culture
©Robert Grant-Downton