Anyone know what this is on Rhubarb leaves?

[Kaymo]

Hi,
Would anyone be able to advise me what these patches are on Rhubarb leaves and if there is a way to treat it?

Bought the plant about 2 years ago in a local garden centre, and the discolouration on the leaves became apparent shortly after planting. The leaves eventually shrivelled away, and I thought the plant had died, but it has come back again the last two years, although with the same issue. I've never had any Rhubarb from it. Tried removing the affected leaves but then it appears on other leaves so wondering if I just need to dig it out and throw away.

Thanks

 

[RandomGrinch]

It could be rust - which is caused by a fungus...

Pests and Diseases of Rhubarb - GardenFocused.co.uk

From crown rot to leaf damage, we help you identify problems that may affect your rhubarb plant and suggest how to cure those problems.

gardenfocused.co.uk

I've had problems with rust on fuchsia, which are also susceptible.
If you do remove the leaves, don't put them out for composting.

 

[JohnD]

I've grown rhubarb, and don't recognise it.

Have a look at the underside of the leaf for clues. There is also some insect damage.

Could anything have dripped on it?

If you're spraying, you could give it a try with insecticide and fungicide. You won't be getting a food crop off it I think.

 

[Kaymo]

Thanks both. I've been removing the affected leaves and putting in the regular bin, but it keeps coming back. Nothing would have dripped on it, and as it reappears each year I am presuming its a fungus type thing.

From the Rhubarb pests and diseases link, provided by RandomGrinch, I agree it looks like a fungus, and I wondering if the fungus is remaining in the soils or surrounding vegetation and just reinfecting it each year. Its probably not worth buying fungicides for one plant so maybe I should just see how it goes this year and if it goes the same way as previous years then I could either bin it, or dig up the crown and move it to another part of the garden.

 

[JohnD]

if you mulch the ground, it will prevent disease spores splashing up in heavy rain

 

[Kaymo]

if you mulch the ground, it will prevent disease spores splashing up in heavy rain

Thanks. That's easy enough to do so worth a try.

 

[StephenStephen]

Personally, if my rhubarb looked like that I wouldn't worry, and I wouldn't be removing leaves or throwing random chemicals around. Rhubarb likes a lot of food and water, so manure and then mulch on that will help it thrive, even with a few blotches on the leaves.

...and sending rhubarb leaves to landfill or incineration is frankly ludicrous, fungus is everywhere!

: https://www.gardeningknowhow.com/edible/vegetables/rhubarb/can-compost-rhubarb-leaves.htm

 

[JohnD]

BTW, are they getting enough sunlight? The stems of rhubarb are shaded by the leaves, and go red, IIRC they will go green in strong sun.

If I have it right, the colour in the patches may resemble the colour of the stems, and perhaps for the same reason. In the pics the patches don't seem to be dying, so maybe it isn't disease.

I've never had those patches, so I'm just guessing.

 

[StephenStephen]

Personally, if my rhubarb looked like that I wouldn't worry, and I wouldn't be removing leaves or throwing random chemicals around. Rhubarb likes a lot of food and water, so manure and then mulch on that will help it thrive, even with a few blotches on the leaves.

...and sending rhubarb leaves to landfill or incineration is frankly ludicrous, fungus is everywhere!

: https://www.gardeningknowhow.com/edible/vegetables/rhubarb/can-compost-rhubarb-leaves.htm

Sorry for my tone, I'm (ironically) having a general panic about what seems to be increasing general fear about rich natural organic complexity...

You might find your rhubarb does better if you stop cutting the leaves off...

 

[Odds]

Could it be deficient in nutrients?
Feed them.

 

[Kaymo]

Personally, if my rhubarb looked like that I wouldn't worry, and I wouldn't be removing leaves or throwing random chemicals around. Rhubarb likes a lot of food and water, so manure and then mulch on that will help it thrive, even with a few blotches on the leaves.

...and sending rhubarb leaves to landfill or incineration is frankly ludicrous, fungus is everywhere!

Hi Stephen,
I'm not sending leaves randomly to landfill. I put a couple of leaves in the regular bin rather than the green bin last year in case it was a disease, I didn't want to be sending it to someone else. This is not an over reaction to a few blotches this year, they have spread and the plant has died back the last two years in a row.

 

[Kaymo]

BTW, are they getting enough sunlight? The stems of rhubarb are shaded by the leaves, and go red, IIRC they will go green in strong sun.

If I have it right, the colour in the patches may resemble the colour of the stems, and perhaps for the same reason. In the pics the patches don't seem to be dying, so maybe it isn't disease.

I've never had those patches, so I'm just guessing.

Plenty of sunlight where they are. In previous years the leaves have died. I am now second guessing whether it is the same issue as previous years, maybe I should just leave it and see if the same thing happens again.

 

[Kaymo]

Could it be deficient in nutrients?
Feed them.

Its possible, but as per my earlier posts the same thing has happened the last two years and the leaves then stalks have eventually died. I haven't been feeding them before, but there isn't really any competition close to them, and in the same area there are chives which are thriving.

Maybe I can try feeding them and just leaving them to see if any different this year.

 

[Kaymo]

Sorry for my tone, I'm (ironically) having a general panic about what seems to be increasing general fear about rich natural organic complexity...

No worries. That's not me. I would have ignored the patches but for the fact that it's been three years now and every year the leaves eventually die.

You might find your rhubarb does better if you stop cutting the leaves off...

I didn't cut anything off the first year or the second. I removed one leaf when I saw the patches again this year to see if I could stop it spreading.

 

[jj4091]

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