A Year of Plant Pathogens

I have recently become very interested in plant pathogens. Here I will document the different species I see in Ireland, organised by month. I hope this site will be a useful resource, both as a reference and to inspire people to take notice of these underappreciated organisms. They are incredibly diverse in form and ecology, and are so ubiquitous that they cannot be ignored. I originally was only recording fungi and oomycetes but have since expanded to all gall-forming organisms.

New species to Ireland (twenty-two fungi, seven oomycetes, a mite, two midges, and a nematode as of 24/10/2024)

30^th March 2024
Ramularia septata on Galanthus cf. nivalis from Orangefield Park.

9^th-10^th April 2024
Mycosphaerellaceae sp. on Escallonia sp. in North Down. Note both Septoria escalloniae and Mycosphaerella escalloniae are known from this host, and can only be distinguished microscopically (I'll get round to it eventually...).

12^th April 2024
Albugo leimonios on Cardamine pratensis in Clement Wilson Park in the Lagan Valley.

12^th April 2024
Entyloma fumariae on Fumaria sp. in the Lagan Valley.

21^st April 2024
Urocystis primulae on Primula vulgaris at Killard Point. Note the white conidia around the anthers and the black spore mass in the ovary.

30^th June 2024
Peronospora fulva on Lathyrus pratensis in Moreland's Meadow, Lagan Valley.

2^nd July 2024
Septoria anthyllidicola on Anthyllis vulneraria in our garden in East Belfast. Note the small, dark pycnidia (fruiting bodies in the leaf tissue) which have burst open to release conidia. This species has not been previously recorded in Britain or Ireland, so it was a particularly exciting find. Septoria has recently been discovered to be far less host-specific than previously thought (Verkley et al., 2013) so it may be lumped into another species.

9^th-10^th July 2024
Pucciniastrum on Soleirolia soleirolii in Acaill, Mayo. This taxon was discovered by Chris Preston in Cambridgeshire. Its identity is unknown - see Preston, C. D., Harries, D. J., & Stringer, R. N. (2023). A newly discovered rust on Soleirolia soleirolii. Field Mycology, 24(1), 13–17.

10^th July 2024
Pucciniastrum guttatum on Sherardia arvensis in an Caol, Acaill, Mayo.

10^th July 2024
Entyloma on Ranunculus baudotii in an Caol, Acaill, Mayo. This is an undescribed Entyloma species in the Entyloma eburneum complex. This group has not been recorded on R. baudotii before so it may be new to science, or it could be the same species as infects other Water Crowfoots. The species on Crowfoots haven't been studied yet so its taxonomy remains unclear.

11^th July 2024
Septoria on Bellis perennis in Bun an Churraigh, Acaill, Mayo. There are two species of Septoria on Bellis perennis according to Unamuno (1942):

Septoria bellidis - spores up to 35μm
Septoria bellidicola - spores 72–104 × 1.5–2.5μm

This one has spores around 50–60μm so it's unclear if it is either. Septoria has been discovered to be far less host-specific than previously thought (Verkley et al., 2013) so no matter what it is, it will probably be lumped into something else eventually.

15^th July 2024
Peronospora sparsa on Rubus fruticosus agg. in Tyrone. Note some authors consider Peronospora on Rubus to be a separate species (P. rubi).

20^th July 2024
Puccinia asperulae-odoratae on Galium odoratum in Black Mountain, Belfast. This is often considered a junior synonym of the widespread P. punctata which has been found in Ireland previously.

22^nd July 2024
Sphaceloma symphoricarpi on Symphoricarpos albus in Tyanee, Derry. The pycnidia are very small, pale brown, and inconspicuous! Thanks to Matthew Rogers for ID.

25^th July 2024
Septoria posoniensis on Chrysosplenium oppositifolium in Cregagh Glen. There are only three previous records on this host, but the spore size matches the description from other Chrysosplenium species.

26^th July 2024
Erysiphe akebiae on Akebia quinata in Botanic Gardens, Belfast. This is probably a recent introduction as there are no British records before 2002.

28^th July 2024
Leptosphaerulina myrtillina on Vaccinium myrtillus in Cottage Farm, Tyrone. This one is definitely extremely common - I remember seeing it in the Mournes before.

1^st August 2024
Claviceps humidiphila on Dactylis glomerata in Belvoir, Lagan Valley. This was recently split from C. purpurea sensu stricto and can be distinguished as it floats in water. Some of the previous Irish records of that species are certainly this one.

1^st August 2024
Sphaerulina gei on Geum urbanum in Belvoir, Lagan Valley.

7^th August 2024
Ramularia episphaeria (=Phacellium episphaerium) on Stellaria palustris near Banbridge, Armagh.

16^th August 2024
Podosphaera phtheirospermi on Euphrasia sp. at Killard Point NNR, Down.

16^th August 2024
Entyloma matricariae on Tripleurospermum maritimum at Killard Point NNR, Down.

27^th August and 13^th September 2024
Cecidophyopsis atrichus on Rabalera holostea (left) and Stellaria graminea (right) in Down. This mite seems to be rather underrecorded.

3^rd September 2024
Dasineura "B" sensu Harris on Filipendula ulmaria in Derry. An undescribed Dasineura gall midge. It is apparently common in Britain. Thanks to sk53 on iNaturalist for ID.

8^th September 2024
Contarinia dipsacearum on Succisa pratensis at Murlough NNR, Down. One or several larvae sit at the base of an unopened flower. The tell-tale sign is that galled flowers are surrounded by open flowers, as if they should also be open. There is only a single other record for this species from Ireland or Britain, from London in 1947. It may turn out to be genuinely rare, though the subtle symptoms means these flower-galling Dasineura are easily overlooked.

13^th September 2024
Subanguina graminophila on Agrostis stolonifera at Lagan Meadows, Belfast. A nematode gall. There are very few global records but it is probably extremely underrecorded. Within a week I found it at two other sites so it is probably widespread and common in Ireland.

16^th September 2024
Bremia taraxaci on Taraxacum agg. in South Armagh.

20^th September 2024
Peronospora trifolii-repentis on Trifolium repens in Ballymorran. This one appears to be genuinely rare. I had been looking for it fairly intensively all year! Then again the symptoms are very subtle and probably easily overlooked, even when searching for it.

11^th October 2024
Pseudophaeophleospora atkinsonii on Veronica (Hebe) salicifolia in a garden in East Belfast. This species is from New Zealand like its host. It has distinctively brown conidia.

23^rd October 2024
Gibbera andromedae on Andromeda polifolia in a lowland raised bog near Randalstown, Antrim.

24^th October 2024
Entyloma ranunculacearum on Ranunculus acris beside a lowland raised bog near Randalstown, Antrim. Another species in the hyperdiverse Entyloma eburneum complex which infects many species of Ranunculus.

16^th November 2024
Peronospora sp. on Veronica (Hebe) speciosa in a garden at Ballyhornan, Down. This is usually recorded as Peronospora grisea but is actually one of the many undescribed species infecting Veronica (Thines & Choi, 2016).

16^th November 2024
Peronospora schachtii on Beta vulgaris subsp. maritima on the Sheepland Coast, Down.

References

Thines, M., & Choi, Y.-J. (2016). Evolution, Diversity, and Taxonomy of the Peronosporaceae, with Focus on the Genus Peronospora. Phytopathology, 106(1), 6–18. https://doi.org/10.1094/PHYTO-05-15-0127-RVW