Pear leaf gall Gymnosporangium sabinae on juniper
Harry Green & James Wade
Pear leaf gall (Fig. 1.), caused by Gymnosporangium sabinae, was first reported in Worcestershire around 2005 (Green 2006, Green 2007, Umpelby 2007). At the time Green (2006)) wrote as follows:
“The disease is caused by the rust fungus Gymnosporangium sabinae (= G. fuscum), which requires two hosts, pear and juniper, to complete its life cycle. Spores produced from the fungal growths on pears are airborne and infect junipers; spores produced from the fungus-induced swellings on juniper stems are airborne, travelling up to 6km, then re-infect pears. The life cycles of Rust fungi are complex. A useful description is given by Spooner & Roberts (2005)”. The alternate host is apparently Juniperus sabina, an evergreen garden shrub sometimes called Buffalo Juniper, which grows to around 3 m in height and two metres across although other juniper species may be used.
Since 2005 the leaf gall has often been noticed on pear leaves throughout the Worcestershire varying in abundance from year to year. In March 2013 James Wade sent me (HG) photographs of the fungus on the alternate host, a garden juniper, taken in April 2012 near Hanley Swan (SO8043), Figs. 2 & 3, with the comment that they showed both the fungus fruiting bodies and the strange cankers or swellings that they leave behind. This is apparently the first record of Gymnosporangium sabinae on juniper in Worcestershire.
The gall on pear is reported to occur on fruit as well as leaves although the former has not been reported in Worcestershire. We should be glad to see pictures of the gall on fruit and also to receive further records from juniper. It would be helpful if the species of juniper could be identified.
Green, H. 2006, Pear leaf gall caused by the rust fungus Gymnosporangium sabinae. Worcestershire Record. 21:49.
Green, H. 2007. Pear leaf gall caused by the rust fungus Gymnosporangium sabinae Worcestershire Record. 22:33
Spooner, B. & Roberts, P. 2005. Fungi. Harper Collins New Naturalist Library number 96
Umpelby, R. 2007. Pear Rust. Worcestershire Record. 22:34
Fig.1. Gymnosporangium sabinae on pear leaves. Rosemary Winnall
Fig. 2. Gymnosporangium sabinae on juniper. James Wade
Fig. 3. Gymnosporangium sabinae on juniper. James Wade