Grow Your Own Magazine

i've just had to destroy the tomatoes in my greenhouse border, how do i prevent this recurring next year?

It won't be easy, your options are to hope for a hot and sunny summer, spray with a fungicide, keep the greenhouse door shut.

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Mark

Vegetable Kingdom blog

Prehaps grow blight resistant varieties?

Steven

i grew ferline outdoors and even that got it!

i should think we are all hoping for a hot and sunny summer after these last 2!

You can spray with Bordeaux mixture every fortnight. It will help stave it off but won't cure it. Approved by soil association.

Unfortunately I was away during later part of August and have lost 8 rows of spuds and 30 tomato plants. Very irritating.

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Paul

What a shame Moonshadow. My beautiful tomatoes got blighted too. It's a problem I've never had before but this is the plan for next year.
Grow early maturing varieties (I believe blight doesn't arrive until August)
Limit the plants to 1 or 2 trusses and get them early.
I'll spray if I have to - but I don't want to
But I don't want to bin beauties like these again.

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From each according to his ability, to each according to his needs.

Has anyone had a re occurrence of blight in a greenhouse after having it the year before?
Not I mean when blight is all around them, but early on. Because I've never heard of it.
Everyone also talks about diseases building up in greenhouses soil when you grow tomatoes in it, yet Mr Flowerdew said it took his, I think 15 to 20 years to build up.

I only grow tomatoes outdoors & the last couple of years they've been struck by blight because of all the wet weather. It's supposed to be rarer on greenhouse tomatoes because they are largely protected by the glass but as Moonshadow has had it & a few others too it's obviously becoming more widespread. If you don't want to use any sprays ( & they don't always work anyway!) the best you can do is dispose of any affected plant material (not in your compost) & thoroughly clean the greenhouse. The blight spores are not supposed to remain active on the surface of the soil but if you wanted to be doubley safe you could skim off the top couple of inches of the border & replace with fresh compost. I've been told by a couple of experts that it's O.K. to dispose of used grow bags which have had blighted toms. in them in your compost bin as the spores would not survive in the bag. Other things to try are to not get the foliage of your toms. wet when watering as the spores love the damp, wash your hands well if you remove any blighted leaves/toms. etc. as you will carry it to the next plant & try not to leave the greenhouse door open on damp windy days.

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Into every life a little rain must fall.

Could someone please explain how blight spores could then stay in the border soil in a greenhouse. Because I am not believing it.

I'm giving up on my tomatoes next year, this is the third year they've got blight. They're outdoors and I'm against it for that. I think I will leave it for two years and see if the spores are out of the soil.

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Best wishes
Andrewo
Harbinger of Rhubarb tales

That's right, the spores are airborne and can travel from miles away or can survive in the affected plant. I suppose it is possible for diseased tomatoes to drop off the plant and remain undetected in the greenhouse soil. But I would think the tomatoes will rot over winter so it's more likely that the spores are blown in by the wind. It's the same with potato tubers; that's why it is recommended to buy new seed potatoes that are certified disease free each year.

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Mark

Vegetable Kingdom blog

Thanks Capsid, thats what I was thinking.
Also for around 3 years I composted my blighted tomatoes and never had a problem, I only started throwing them away after being repeatedly being told I was doing it wrong. I'm not convinced you can't compost them (properly) either.

Well, the spores come from somewhere, so there must be a place that they overwinter. I don't think they survive very cold conditions in the soil such as our UK winters.

Source: EB0958 Late Blight of Potato and Tomato and Its Control in the Home Garden

ETA: later on in that article, it advises against composting since the pile may not get warm enough to kill the spores.

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Mark

Vegetable Kingdom blog

Interesting, that article says:

"Do not place [infected plant parts] on the compost pile (back yard compost piles may not reach sufficient temperatures to kill specialized survival spores called oospores, if they are present)."

Detective Demeter scours the internet to find what the b***y hell oospres are anyway...

It appears (from what I can make out) that these oospores are "hardy" blight spores which only form if compatible strains of blight infect the same plant and then mate with one another and produce viable progeny. So this will only happen if both of the necessary strains are present, and even then is not certain.

If oospores are produced, they can survive away from the infected material (which other spres can't) and might be able to survive temperatures from -20 up to 43 degrees C. A compost heap or bin would normally exceed that temperature, I believe, at least if it is looked after "properly" - I think they can get up to around 60 degrees - although I guess if you just have a smallish pile in the corner which you never turn then it may well not get that hot?

Late Blight Workshop Paper - Fry
Phytophthora infestans

From all this, I would conclude that composting blighted material MIGHT cause reinfection the following year, but only if the right kind (or rather the wrong kind!) of oospores happen to have been produced and only if your compost heap does not heat up sufficiently for them to be killed... As others have suggested, it seems much more likely, if you get it, that this will be from airbourne spores, presumably from the bloke down the road who left his blighted tubers in the ground and allowed the spores to overwinter there... Grr.

(Anyway, it makes me a feel a whole *heap* better (geddit) about binning my tomatoes as I was only about 80% sure that they didn't have blight...)

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Warning: I have a dangerous tendency to act like I know what I'm talking about.

Looking at the blightwatch maps, blight always seem to be first near the sea, either from abroad or because temps are higher there?

I don't get it, if you bin them, then they just end up on the council run landfill. Is it me?

I think the spores can get blown from abroad

I think this means the green bin for garden waste recycling, the council composters reach a very high temperature and will kill spores.

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Mark

Vegetable Kingdom blog

I don't have a council green bin for composting, nor do alot of people. I would have a large bet that most of the blighted tomatoes go into the normal bin.
What does this mean? It means, the more I write about this, the more I am convincing myself the chances of it being passed on in your garden from year to year is minuscule.

Ive got blight on my outdoor tomatoes but none on the ones in the greenhouse or the one pot in the conservatory. Now I am worried about putting the rotten plants in the council bags for passing on these spores. Would it be better to burn them?

missycass - if the council bags are for council composting then there should not be a problem as the large-scale composting they do will easily get hot enough to kill even the oospores.

From what I was looking at yesterday I think even a decent home-composting system should get hot enough (my dalek certainly does) and anyway I get the impression that the formation of oospores (the hardy ones) is pretty unusual - and the normal ones would certainly not survive composting as they need to be on plant material and the plant material itself would be rotting down.

Based on what I've seen so far, I'm of the same view as Womble. I am and always have been a great believer in the power of composting to kill nasties.

e.g. - weblife.org: Humanure Handbook: Chapter 3: Compost Miracles
(If you've never read this then prepared to be amazed!)

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Warning: I have a dangerous tendency to act like I know what I'm talking about.

Well, from my research, the spores can and do indeed survive the compost heap - the key is that they survive on infected plant material. Not everything in a heap rots equally, nor at the same temperature. You would have to have some serious monitored system to ensure all nasties had gone. Most amateur gardeners do not get hot heaps purely because they cannot get enough waste together at once.

The soil and compost issue is different, however - if you remove all the plant material, spores cannot survive. It has been found that spores blow in rather than remain in the soil to re-infect the next year's crop. Some spores do metamorphose, but not so much in UK, I believe.

Basically, you need to be responsible as a grower for yours and everyone else's future crops - you need to dispose of your blighted material carefully - by burning or sending to an appropriate green waste facility - or the problem will continue.

In theory - ok, it's not ever going to happen - if everyone burnt the infected stuff at the same time, we'd kill off all the spores! It's not quite as simple as that, but you see the point. In the UK, re-infection is usually put down to discarded potato crops - huge amounts of blighted tubers which lie uncovered through the winter. I can't say whether this is an excuse (ie. let's blame the farmers! or a reality)

When it comes to highly infectious plant diseases, just like human ones - hygiene is the key.

Hmm - some of my plants got blight, but others about 3 feet away didn't!

My beef tomatoes got it so badly I've had to dig them up and black bag them - going to take to tip and put in green waste so they can deal with them properly! The rest of them (gardeners delight, Ildi and golden sunrise) appear to be fine so far (fingers crossed). I did feed them recently, and they're all out in the open in a really sunny spot - the beef tomatoes are the only ones not sheltered by a huge tree, so I think that might have been the deciding factor...

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Do not meddle in the affairs of dragons, for you are crunchy and taste good with ketchup.

you poor thing! it's heart-breaking to throw them away. better luck next year!