Collection location: Tahoe National Forest, California, USA [Click for map]
Found on fallen Arbutus menziesii (madrone) leaves near the mushroom expo.
Conidia hyaline & mostly uniseptate.
Conidia range = (21) 22 – 29 (30) x 5.5 – 7 µm
Average conidium = 25.45 × 6.03 µ
Q range = 3.5 – 5.09
Average Q = 4.24
20 conidia measured in H2O.
I’m not sure this species is in ’Westcott’s Plant Disease Handbook’ & I see nothing known from Arbutus at all in Ellis & Ellis.
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sum(score * weight) /
(total weight + 1)
The paper is available online, here.
It pretty much shows the same options as ’Westcott’s Plant Disease Handbook’. Here are some thoughts on the options:
Ascochyta hanseni – With brownish & smaller conidia? http://bit.ly/1e9Gwi0
Cryptostictis arbuti (= Seimatosporium arbuti) – 4-septate conidia? http://bit.ly/1bp5Htv
Didymosporium arbuticola – “Conidia are slime-spores in acervuli; dark, two-celled.” – Westcott’s Plant Disease Handbook
Mycosphaerella arbuticola – Different macro & conidia. http://bit.ly/19d2ttp
Phyllosticta fimbriata – Far smaller conidia. http://bit.ly/K1cFP6
Diplodia maculata – Short Latin description, maybe? http://bit.ly/JbPsd3
There is also Septoria unedonis known from Arbutus unedo, but I don’t have the description (Desmazières, J.B.H.J. 1847. Quatorzième notice sur les plantes cryptogames récemment découvertes en France. 8:9-37). Septoria images I have found online mostly show different kinds of spores though, maybe similar macro at least…
That Diplodia maculata description says it should have brown conidia, also this link corroborates that. http://website.nbm-mnb.ca/...
And the Septoria unedonis description can be seen here on pg. 20, not that it helps very much… http://bibdigital.rjb.csic.es/spa/Libro.php?Libro=2228
I also found this about Septoria, “Most taxonomists adopted a generic concept of Septoria that included fungi forming pycnidial conidiomata with holoblastic, hyaline, smooth-walled conidiogenous cells with sympodial and/or percurrent proliferation and hyaline, smooth, filiform to cylindrical multi-septate conidia (Sutton 1980, Constantinescu 1984, Sutton & Pascoe 1987, 1989, Farr 1991, 1992).”
Bennett, M. and Shaw, D. 2008. Diseases and insect pests of Pacific madrone. OSU Extension Service EC 1619-E
maybe if you can access it there will be reference to this species.