Is this tomato blight, if not any ideas what it is please?

[Russel Sprout]

Hi

Sorry for another tomato blight thread, but after babying our plants and looking forward to the first ripened tomatoes, we don't want things to go wrong at this stage!

We've got around 20-25 plants in all. They're in a poly tunnel. 4 or so plants are affected, and they are next to each other. So far, apart of a couple of fruits, it is only leaves that are effected. The stems are ok as far as I can see...

If it's not blight, any other ideas as to what it is and what needs to be done?

I've done a fair few photos to help with the diagnosis!

Many thanks

[Russel Sprout]

And some more photos:

[ameno]

No, that's not blight.

It looks like a severe nutrient deficiency. The purple is definitely magnesium, but the pale brown leaf margins and the yellowing are probably something else, perhaps potassium. Or, well, it probably needs everything, to be honest.
Any, give it a good feed up and feed it with a good tomato feed (one which contains magnesium) once a week.

Blight produces large, irregularly shaped dark brown blotches on the leaves and stems, which spread very quickly. The patches are a wet rot, so they rarely is ever dry up or shrivel up, so it's a fair bet that any dry brown patches are not blight.

[nickdub]

I agree, definitely a feed problem not blight - all I'd add to a liquid feed is also to spray with something like seaweed mix as a foliar feed - sometimes the leaves can absorb nutrients faster than the roots - so I'd do both.

PS don't be tempted to make the feed any more concentrated than recommended by the manufacturer, as an overdose can be worse than an underdose.

[Peteyd]

I had a very similar situation last year (about this time too!). As other have said, and more will probably will say, it doesn't look like blight.

Give it a good feed of either a tomato specific feed or liquid seaweed both diluted as per the bottle. I would cut the damaged leaves back though, any damage like that won't heal and it can be a great entry point for a disease.

As a side note, some say you can cut all the leaves off up to the first truss. this will help improve airflow and help in the fight against blight taking hold. These past couple of weeks has been rather hot and very humid (at least it has here!) which is almost perfect conditions for blight.

[mrbadexample]

I get leaves like this quite often - I figure they're just old. They don't seem to make any difference to the fruit.

Yesterday I went round all the tomatoes removing anything old, yellowing or like that. All were low down on the plant & the leaves higher up were fine. Just a bit of tidying up to help with airflow etc as stated above.

Nothing to worry about if you ask me.

[peanut]

I get the same brown marks on my toms in the greenhouse, I think it is caused by condensation on the leaves and then the sun scorching them. I just snip the damaged bits off. It doesn't affect the plants.

[Russel Sprout]

Hi all

Apologies for not coming back to this sooner. I don't know where the days go!

First and foremost, thanks for all the helpful replies

It looks like a severe nutrient deficiency. The purple is definitely magnesium, but the pale brown leaf margins and the yellowing are probably something else, perhaps potassium. Or, well, it probably needs everything, to be honest.
Any, give it a good feed up and feed it with a good tomato feed (one which contains magnesium) once a week..

I use homemade comfrey liquid to feed the tomatoes. Should that have sufficient magnesium and potassium? I always just presumed it was a good all rounder and contained everything needed. If that is the case, then perhaps it's more that I have not been giving them enough? I've been feeding on average about every ten days.

I agree, definitely a feed problem not blight - all I'd add to a liquid feed is also to spray with something like seaweed mix as a foliar feed - sometimes the leaves can absorb nutrients faster than the roots - so I'd do both.

Interesting – I’ve never used foliar feeds so definitely something to look into. I presume it’s best to use them when it is cooler to prevent scorch?

PS don't be tempted to make the feed any more concentrated than recommended by the manufacturer, as an overdose can be worse than an underdose.

I use around 200-250ml of comfrey feed per large watering can. My comfrey feed is the undiluted type; thick and black!

As a side note, some say you can cut all the leaves off up to the first truss. this will help improve airflow and help in the fight against blight taking hold. These past couple of weeks has been rather hot and very humid (at least it has here!) which is almost perfect conditions for blight.

Yes, we’ve been doing that – removing all leaves up to the first truss. It helps with watering too.

I get the same brown marks on my toms in the greenhouse, I think it is caused by condensation on the leaves and then the sun scorching them. I just snip the damaged bits off. It doesn't affect the plants.

We get condensation in th PT too. And in all honesty perhaps we've been a bit slapdash when watering in the past and the lower leaves may have got wet. Possibly the low fruit too. So removing the lower leaves has helped with that.

…….

Well, it's been ten days since I first posted, and looking at the toms this morning we noticed more that have problem in the upper sections of the plants. Unlike before, there is now some discolouration on the stems too. We've snipped these bits off - photos below. Not sure if this is something different or a continuation of the same problem.

Thanks again to everyone for the great replies.

[Russel Sprout]

[Penellype]

That looks like blight to me I'm afraid.

[ameno]

That, however, is definitely blight.

[Russel Sprout]

OH NO!

OK, we're on it to remove anything that looks slightly affected from the poly tunnel. The healthy looking plants that remain in the polytunnel - is it only a matter of time now? Or might they get away with it? Is there anything we can do to prevent the spread?

Out of interest - and so we can learn for the future - one of the original photos was this:



When you compare it with the two photos above showing the cuttings on the concrete, what makes those blight and this one not?

Another photo taken just now... Is this the start of blight? :-




And on this plant, all is looking well aside form this leaf:





Confession time... We did have some potatoes growing from last years tubers. Possibly even the year before's! They came up, and - us being very busy and none the wiser - we thought we'd leave them in. We suspect they got blight recently and am starting to wonder if this is where it's come from.

I've got some more photos - including a couple of the remains of the potato plants - but though rather than upload them here I'd bung them on Google Drive for anyone to take a peek.

Many thanks for all the help. I'll get there one day!

https://drive.google.com/drive/folde...Ax?usp=sharing

[Nicos]

D'oh...sorry to hear that. I think we all wait with baited breath to see when/if we get blight.

If I recall correctly it takes 2weeks for an affected plant to show symptoms, so it's more than likely already affected any other plants nearby.
At first sign pull off the green fruit but don't leave them too long to ripen on the windowsill as they too are more than likely to start going brown -and the flavour is yuk and taints everything.
Cook them down green so as not to waste them if that's the case.

[Russel Sprout]

We're quite fond of green tomato chutney, so I guess it isn't all bad! Thanks for the tips. So Nicos - do you agree with the others that it definitely looks like blight? It's just that I asked elsewhere at the same time and the jury is out with the guys there as to whether it is blight or Botrytis.

Cheers

[ameno]

I don't think any of those other photos are blight. They look like the same nutrient deficiency from before.

What makes the blight infection recognisable from those other brown leaves is the colour (it's markedly darker brown, whereas the other crispy brown leaves are more beige), the fact that it's also on the stems (a dead giveaway) and, if you watched it over a few days, the rate of spread. Blight spreads very quickly. Also, blight-infected leaves generally stay soft and limp, rather than going dry and crispy, although in hot weather like we've been having even blighted patches will go crispy, so that's not such a reliable test.

If I recall correctly it takes 2weeks for an affected plant to show symptoms, so it's more than likely already affected any other plants nearby.
.

Outdoors it will certainly spread very quickly. It can be contained somewhat better undercover if you catch it early enough, as the blight spores require a wet leaf or stem surface in order to germinate, so if you cut out all infected material and make sure you do no allow the leaves to get wet, it should greatly slow its spread (although you likely won't outright stop it).

On the subject of infected fruits, the flavour is tainted as soon as the infection begins, but the browning only comes later, so you need to spot the early signs of infected fruit. They develop an uneven skin surface with small dimples, and a sort of swirly pattern on the skin, often with a very slight yellow tint.