Observation 198732: Phragmidium Link

on stems of California Blackberry, many of which were flowering.
Possibly P. violaceum? with those somewhat angular spores and lack of any other
distinctive structures (at least above the stem surface).


Proposed Names

47% (2)
Recognized by sight
28% (1)
Recognized by sight: Rust known on Rubus ursinus in California.
Used references: Arthur 1934
28% (1)
Recognized by sight: Rust known on Rubus ursinus in California.
Used references: Arthur 1934 (Kunkelia nitens in the literature)

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= Observer’s choice
= Current consensus


Add Comment
With rose rusts
By: Byrain
2015-02-14 12:41:07 CST (-0500)

Teliospores appear after the urediospores and can even be found at the same time like obs 96900. I imagine its likely the same here, but many rusts have teliospores only on entirely different hosts. Arthur 1934 is a really good reference for rusts, even now, but without teliospores you will be left hoping that the host index doesn’t return too many options. I will e-mail you some more specific references for rusts on Rosaceae.

Edit: Either I’m misremembering what pdfs I had or my Rosaceae rust literature is only useful for roses…

I was unable to find
By: Christian (Christian Schwarz)
2015-02-14 11:57:33 CST (-0500)

any other distinctive structures – maybe these colonies are too mature?
Do they produce telio/uredio spores at different times?

Given that these are likely commercially important, there should be a good reference somewhere online. Does anyone have any leads?

Other options on Rubus.
By: Byrain
2015-02-14 11:53:27 CST (-0500)

From Westcott’s Plant Disease Handbook under Rubus.

“RUST, Late. Pucciniastrum americanum (II, III), Northeast to ID, IL, NC,
OH; 0, I on spruce.
RUST, Leaf. Phragmidium rubi-idaei (0, I, II, III), northeastern and central
states to CO; Pacific Northwest.
RUST, Orange. Gymnoconia peckiana (0, I, III), on black raspberry, North-
east to MN, Pacific Northwest; Kunkelia nitens (I), IL, IN, MI, OH.
RUST, Yellow. Kuehneola uredinis (0, I, II, III), IL, PA, DE to WI.”

Also, teliospores go a long way for Phragmidium, urediospores without electron microscopy seems rather hopeless. (How many germ pores do they have?)