First report of honeysuckle leaf blight (Insolibasidium deformans) on honeysuckle (Lonicera spp.) in the UK

P.A. Beales^1*, J. Scrace², R.T.A. Cook³, A.V. Barnes¹ and C.R. Lane¹

¹ Central Science Laboratory (CSL), Sand Hutton, York, YO41 1LZ, UK
² Freelance plant pathologist, 25 Maslan Crescent, Tibberton, Shropshire TF10 8PB, UK
³ Consultant plant pathologist, 30 Galtres Avenue, York YO31 1JT, UK

*p.beales@csl.gov.uk

Accepted for publication 12/02/04

Honeysuckle belongs to a popular genus of ornamental shrubs (many of which are climbers), grown mainly for their fragrant flowers. Over the last few years, many species and varieties of honeysuckle have become affected by a pathogen newly introduced into the UK: the basidiomycete Insolibasidium deformans, which causes honeysuckle leaf blight. The disease was first observed in the UK in early summer 2000 on a containerised plant of Lonicera pileata. Since then, the disease has become more widespread in the UK on Lonicera spp., especially in the south of England. Symptoms are first seen in the spring as interveinal chlorotic lesions on newly emerged leaves. As these lesions develop, they become yellow/brown and turn silvery as they dry out (Fig. 1). 

Figure 1: Yellow/brown necrotic lesions and silvery appearance to dried lesions on upper leaf surface

A curling or twisting of entire leaves is often seen and affected leaves often drop prematurely. Stems appear to remain symptomless. A white bloom consisting of basidia and basidiospores is evident on the undersurface of infected leaves (Fig. 2). Basidia observed on UK samples were four celled, cylindrical, curved (4–6 x 20–35 µm) with short cylindrical, slightly curved, hyaline, apiculate basidiospores (5–7 x 9–13 µm) that conformed to I. deformans (Oberwinkler & Bandoni, 1984). Pathogenicity was tested by dusting healthy plants of L. pileata and L. nitida with basidiospores from an infected plant. Uninoculated plants were used as controls. Typical interveinal chlorotic symptoms were observed after a few weeks on L. pileata, but not on L. nitida. No symptoms were found on the control plants.

Figure 2: White bloom of basidia and basidiospores Insolibasidium deformans on lower leaf surface.

Honeysuckle leaf blight has previously been recorded on Lonicera in at least fourteen north-eastern and north-central states of the USA and from Canada (Riffle et al. 1986). This is the first report of the disease in the UK and the pathogen is now considered to be established here.

References

Oberwinkler F, Bandoni R, 1984. Herpobasidium and allied genera. Transactions of the British Mycological Society 83, 639-658.

Riffle JW, Watkins JF, 1986. Honeysuckle leaf blight. In: Riffle JW, Peterson GW, tech. coords. Diseases of tress in the Great Plains. General Technical Report RM-129. Rocky Mountain Forest and Range Experiment Station, 26-29.

The British Society for Plant Pathology