Heuchera disease: which one?

Papi Jo

The most vigorous of my heucheras, H. 'Chocolate Ruffles' are still vigorous this season, except that upon looking closely for a few days I see worrying signs on the foliage. For now I have just deleted all the affected leaves, but it continues and I hope I will not have to tear everything away.
For the moment none of my other varieties of heucheras are concerned.
On the internet, there are several mentions of diseases of the heucheras: "The heucheras fear rot in soil that is too humid, the adult vine weevil perforate the foliage while their larvae attack the roots." OK, I've already had vine weevil attacks, but this is not the case.
Rust is also mentioned for heucheras here:

https://www.gardenfocused.co.uk/plants/ ... a-rust.php

or on the RHS website here: https://www.rhs.org.uk/advice/profile?pid=774

but the images do not seem to match, I do not have pustules, but areas that make me think of a virus (mosaic type).
I do not think it is burns (sun or frost) either.
Have you ever noticed this problem on your heucheras? Can some one identify the disease? and a treatment?

nultyphilip224

@Papi Jo ,..looks like something moist was dropped on the foliage and the sun then scorched it,..as you say a few diseases have cropped up with Heuchera's and Heucherella's,..so far i have not had any signs of disease,..nor i might add on my Hollyhocks,..the latter i am testing with a Neem Oil Mix.

I spray all my Heuchera Plants and all my other plants,..nothing amiss.

The mix has so far prevented all known mites and insects that eat foliage in my own garden,..the advantage is that its a Natural Oil,..Organic,..have a read in the link below,..it might well be the answer to helping you stem the disease if it be one,..either way it will be of use in the garden anyway.

https://www.thespruce.com/using-neem-oil-as-an-organic-insecticide-2132579

Papi Jo

Thanks for that tip, @nultyphilip224. However, I'd rather identify the exact nature of the problem before applying any solution.

Currently I am just removing the affected leaves and watching for any development. I'll post any further developments in this discussion.

Papi Jo

It's happened again! Same cultivar, Heuchera x 'Chocolate Ruffles'. Some pics taken this morning.

Diseased leaf - close-up

Front: normal leaf on the left / diseased leaf on the right

Reverse: normal leaf on the left / diseased leaf on the right

Diseased leaf seen in contre-jour

AnniD

Any use @Papi Jo ?
https://web.extension.illinois.edu/focus/index.cfm?problem=diseases-of-iheucherai-sp-coral-bells

Papi Jo

Thanks for the reference, @AnniD .

jameshtracey

I am the IPM manager at a large nursery that produces a large amount of Heuchera and I have yet to send that particular problem to the provincial diagnostics lab for proper identification but I have seen it. As Heuchera tends to be a shade loving plant I have treated it as abiotic, likely sunscorch. To be certain, it is unlikely fungal as the pattern of "infection" does not cross the veins for the most part. So if it is pathenogenic, it would likely be bacterial or viral. In either case the only true solution is removing the affected leaves.

Papi Jo

Thanks for your message, @jameshtracey

I do know that Heuchera do not like the sun in general (depending on the cultivar). As you and others have said it could be sun-scorch. Anyway, the problem does not seem to spread and removing the affected leaves is the solution I have used last year (and will do this time too).