Author Topic: preventing next years blight  (Read 6743 times)

ACE

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preventing next years blight
« on: August 30, 2015, 08:32:38 »
Everyone of us has been wiped out with blighted tomatoes, I am going to bag mine up this morning, what should I do with them. (fires not allowed until winter). Also I have been looking at cleaning the ground, loads of advice from people I don't know on the internet that might just be spouting. This include, mild bleach, digging often to disturb the spores, warming the soil, cooling the soil, mulching, not mulching. I have never had blight before so any 'real' advice where your 'cure' has worked firsthand would be welcome. Crop rotation I know about. It is limiting the spores that I want to find out about if that is even possible. I did read about a baking powder/washing up liquid mix for lawn fungi, I am wondering if it would work on the lottie, seems better than killing all the worms etc with  jeyes or something worse.

BarriedaleNick

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Re: preventing next years blight
« Reply #1 on: August 30, 2015, 09:19:56 »
From what I have read it is pointless to treat the soil or more accurately know one seems to know if infection can occur from soil borne sources.

From the RHS

The pathogen overwinters in rotten potatoes left in the ground or by the sides of fields. However, the great majority of infections in gardens arise from wind-blown sporangia originating in other gardens, allotments and commercial crops.

and

The pathogen can also produce resting spores (oospores) in the plant tissues that can contaminate the soil. Little is known about their survival and their potential as a source of the disease. The investigations into oospores are continuing and more information may be available in a few years. 

Even if oospores are a source of infection it is pretty unlikely that much could be done chemically without damaging the soil.  Spores are generally pretty hardy things.

We always get blight and we are in the middle of London but most years we get a decent crop with a bit of luck and some copper based treatment.  If it is in the middle of the season then I generally just remove the affected plants and spray the rest.  If, as normal, we get it later in the season when it turns wetter, then I just remove the whole lot.  Sometimes I just bag and bin it or if I can get away with a fire then I burn them.  Some say to bury it - at least a foot and half deep or compost it if you have a proper hot heap.  I think good plot hygiene - clearing away plant and fruit debris - is the best thing you can do.  What drives me nuts is seeing rotting blighted plants on a plot where the gardener just leaves them.
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Redalder

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Re: preventing next years blight
« Reply #2 on: August 30, 2015, 10:16:54 »
Not a cure, but as a preventative, I never include tomato or potato shaws in my compost heap/bins. I store them separately and put them in my garden waste collection bin to be picked up by the local authority who compost at a far higher heat than I can manage.

sparrow

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Re: preventing next years blight
« Reply #3 on: August 30, 2015, 11:25:36 »
Also in London - we always get blight, but late in the season so thankfully my spuds are rarely affected. I have a hotbin so will chance the haulms, but not the tomato plants, they go into bags for green waste at the tip, together with my horsetail clippings.

Am likewise immensely annoyed when I see blighted tomatoes and spuds just left on our site. People don't take in that it spreads from plot to plot - they are told but they just don't listen.

Personally I wouldn't worry about blight spores in the soil as long as you're disposing of the plants properly.

ACE

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Re: preventing next years blight
« Reply #4 on: August 30, 2015, 12:27:55 »
Just as I thought, leave well enough alone. We were taking out affected plants, but then the wet spell stopped most people from getting to their plots so now some of you would be having some proper hissy fits at the rows of wilted plants on every plot. Moved mine into bags now so I can walk around the site with a halo.

johhnyco15

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Re: preventing next years blight
« Reply #5 on: August 30, 2015, 16:43:49 »
as yet i say this with everything i have crossed we no blight on our site from toms to main crop pots are all green and healthy :sunny: :sunny: :sunny: :sunny: :sunny: :sunny: :sunny: :sunny: long may it continue sorry to hear about your site ace :BangHead:
johhnyc015  may the plot be with you

ed dibbles

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Re: preventing next years blight
« Reply #6 on: August 30, 2015, 20:29:35 »
After encouraging results from neighbouring plot holders with outdoor tomatoes I shall be trying myself with them next year. I usually grow them undercover even here on the somerset/dorset border. :happy7:

The season has been so cool with periods of rain you would think their tomatoes would have given up and got blighted long before now but the first signs of it are only now appearing after a very acceptable cropping period.

As we know blight spores are microscopic, all around and carried on the wind to land on susceptible plants when conditions are right, toms and potatoes particularly. A respected allotment blog suggested that outdoor tomatoes always get blighted sometime in august.

If a full tomato crop is the aim it may make more sense to grow bush, non vining, varieties since they tend to set their crop all at once and earlier. A mix of bush varieties or staggered planting might extend the harvest. Defoliating tomato plants drastically in early august may help with airflow, ripening and blight prevention. Something to think about at least.

Or I could simply grow what I can and accept that the blight will hit a some point. :happy7:

winecap

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Re: preventing next years blight
« Reply #7 on: August 30, 2015, 21:19:25 »
As I understood it, the blight is only known to survive long-term in living tissue, so all my blighted tomato and potato plants from last year went into the compost. We have no blight as yet this year, probably because the weather hasn't suited it. Potatoes have been the best ever, but tomatoes are slow. As for preventing next years blight, I think that's out of my hands. The only thing I try to do is remove all volunteers that come up from a previously blighted crop.

telboy

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Re: preventing next years blight
« Reply #8 on: August 31, 2015, 14:53:05 »
Interesting that we've only had one blight alert this year here in north oxon.. Personally, in past years, I've lost all outdoor toms. so only grow in a greenhouse where, I've found, the protection offers a good chance of a viable crop.
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Robert_Brenchley

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Re: preventing next years blight
« Reply #9 on: September 08, 2015, 20:33:49 »
Compost the material; nothing survives overwinter from toms, so there's nothing to fear. The main thing to watch out for is potato volunteers. If you're going to tolerate them at all, lift every one, and only keep unblemished tubers. If everyone only did this, there would be a lot less on allotment sites. The other thing is seed potatoes. 0.2% of blighted tubers is tolerated. So once again, only plant unblemished tubers. Farmer's outgrade piles won't have much influence on city plots.

The amount of the disease depends on the previous year's weather. In a wet season, the disease multiplies and become s rampant, so lots survives in the tubers. After two wet years, we're likely to have an outbreak around midsummer on my site. After a dry year like last year, most of it will have died out, and it takes a long time to build up again.
« Last Edit: September 08, 2015, 20:38:20 by Robert_Brenchley »

Vinlander

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Re: preventing next years blight
« Reply #10 on: December 30, 2015, 19:42:04 »
I absolutely agree with Robert B - potatoes are the real problem - there's certainly no excuse with tomatoes for using an environmentally unsound means of disposal like fire or plastic bags.

Although nothing beats a hot compost heap, I'd like opinions on whether burying tainted stems and fruits (at very end of season) just below the soil surface might actually be safer than putting almost healthy tomato stems in a lukewarm heap that could possibly overwinter them at a temp they like??

Cheers.
With a microholding you always get too much or bugger-all. (I'm fed up calling it an allotment garden - it just encourages the tidy-police).

The simple/complex split is more & more important: Simple fertilisers Poor, complex ones Good. Simple (old) poisons predictable, others (new) the opposite.

earlypea

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Re: preventing next years blight
« Reply #11 on: December 31, 2015, 13:31:13 »
Although nothing beats a hot compost heap, I'd like opinions on whether burying tainted stems and fruits (at very end of season) just below the soil surface might actually be safer than putting almost healthy tomato stems in a lukewarm heap that could possibly overwinter them at a temp they like??

I did that year before last and since learning more about recent blight strains now very much regret it. 

Seems, scanning through this thread that some people are unaware that blight has mutated.  It's no longer a simple case of it being passed on by living tissue (potatoes).   Before there was only one strain that reproduced asexually (ie. in tubers), now there are multiple strains with reproduce both asexually and sexually.

 'During the last two decades multiple and much more virulent lines of P infestans of both mating types have migrated from their place of origin in Mexico to many other regions.  Asexual spores of P infestans (old blight) live only briefly on living tissue.  They live only long enough to blow on to the next living tomato plant".......sexual propagules of P infestans, called oogonia (new blight) are long-lived, however.  They persist in the soil."  Carole Deppe  The Tao of Vegetable Gardening.

Apologies at the snippets copied from a lengthy and  very good explanation from Carole Deppe, but it gives the vocab to google it.  I have read the same elsewhere in books and on the internet.

If you accept the above, with the conditions on allotments; people leaving stuff rotting for whatever reason, it's always going to persist - I really don't think anything can be done except growing early or resistant varieties in those conditions.  If you have some control over your immediate environment, then I think you stand a chance if you eliminate any infected material very quickly, probably not by composting, but certainly not by burying.

Vinlander

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Re: preventing next years blight
« Reply #12 on: January 01, 2016, 12:25:56 »
I would say we have seen several years with relatively manageable blight - certainly controllable with copper. In a really bad year nothing works.

Does this mean the sexual spores are still rare or does it simply mean we are living in a fools paradise - just waiting for the next bit of real blight weather?

If and when sexual spores take over we will still be entirely at the mercy of bad practice by any and every idiot upwind of us.

Analogous to the position we are in now with failing antibiotics.

Or the position we have always been in with dandelions - not that that's an insoluble problem - the only time Paris was free of rats was when it was under siege - yummy rat-a-tu'e.

Cheers.

With a microholding you always get too much or bugger-all. (I'm fed up calling it an allotment garden - it just encourages the tidy-police).

The simple/complex split is more & more important: Simple fertilisers Poor, complex ones Good. Simple (old) poisons predictable, others (new) the opposite.

galina

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Re: preventing next years blight
« Reply #13 on: January 01, 2016, 13:19:21 »
Earlypea, I have always held with HDRA's advice that blighted tomato/potato stems are fine in the compost bin.  I have however always covered them up simply to prevent active spores blowing.  Guess a covering layer of mowed grass does help rapid decomposition as well as preventing spore distribution.  Your post has stimulated a re-evaluation whether this is the best practice?  Are there differences between the pocket handkerchief sized plots in the UK and the many acres that Carol Deppe has at her disposal?  I have sometimes burnt affected potato and tomato plants, but not systematically, only when I had a burn pile in place already with tree prunings etc, because green tomatoes/potato plants on their own don't burn well.  And in a dalek type bin, covered and with lid, I believe there is no risk.

We have never had unusually bad blight here as a consequence of my disposal.  On the other hand we always end up getting it, usually well after the first reports here.  Even this year we had a tiny bit of blight at the end of October!  Greenhouse grown tomatoes escape it due to drier conditions.

Presumably it is still just as true for the new blight strains, that the spores are blown in on the wind, whatever you do and however well you personally have disposed of your plant waste the previous year, but whether these spores get activated depends on the degree of moisture in the air.  Hence the Smith periods and blight warnings.

If spores do persist in the soil, then why are potatoes/tomatoes not at risk during the months of May and June?  Plenty of time for spore activation due to moisture.  Or should I just not say this out loud, because this could be on the horizon  :BangHead:  Presumably everybody follows a crop rotation scheme.  And everybody is moderately diligent about removing blighted plant material and pulls entire plants once the stems are affected. 

I suspect this means that gardeners simply cannot prevent spores being blown in, short of being surrounded by very tall fences and hedges in an urban garden where nobody else in the vicinity grows tomatoes or potatoes.  And secondly that gardeners can prevent (to a useful degree) spores being activated  - by rain covers, sheltered growing under house eaves, greenhouse/poly growing with good ventilation etc.  And of course growing resistant varieties    :wave:

« Last Edit: January 01, 2016, 13:47:44 by galina »

earlypea

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Re: preventing next years blight
« Reply #14 on: January 03, 2016, 13:29:05 »
Galina - I think the simplest answer to all of it is "I just don't know anymore"

I used to compost quickly, I used to bury.  Like you, I presumed getting rid of the spores blowing around was paramount, but now I just don't know what's best.

People say last year was relatively blight-free, but not for us.  Some plots were totally hammered and others were relatively free.  It was a very odd year for it.

Last year's conditions were strange though - incredibly dry (here) through June and July and then although August was wet it was much cooler than optimal (Smith period) temperatures.

Maybe the soil isn't warm enough for us to get blight from soil born spores in May/June (as your question).  I mean that is early in the season - things are just getting going and like the sea, the earth takes time to warm up, does it not?  Maybe the soil born spores need high temperatures?

What I've always found odd, is that my mother always gets blight in her back garden.  No-one grows vegetables round here.  It must be from her tomatoes the year before.  I cannot see any other way.  And she has to-date always used the same pots because I was unaware of soil born spores.

And.....the first blight I saw last year was produced by a guy two plots away who had some very ugly and stunted tomatoes in 2014 which died very early of blight and he planted tomatoes again in the same piece of soil last year.  He had definitely got rid of the plant matter.  Another plot-holder made him.

Like I say, I just don't know.  I'd like to read more, but I'm going to Australia  :glasses9: in a few days to see tomatoes growing blight-free ....bit busy.



Vinlander

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Re: preventing next years blight
« Reply #15 on: January 04, 2016, 11:14:18 »
What I've always found odd, is that my mother always gets blight in her back garden.  No-one grows vegetables round here.  It must be from her tomatoes the year before.  I cannot see any other way.  And she has to-date always used the same pots because I was unaware of soil born spores.

Overwintering sexual spores are definitely a new thing, so if your Ma has had the problem this long it seems extremely unlikely that tomatoes are to blame. It only takes a few tiny volunteer potatoes barely hanging on to life at the back of a shady bed (I had this once) to guarantee she becomes the source of all the blight in the area. 

That raises a thought - I suspect the Sarpos are even more likely to become symptomless carriers? (or mildly raddled ones). I love collecting that kind of downside-risk Urban Myth!

Actually the most likely explanation (especially if nobody else grows veg) is that she has an abandoned area full of volunteers somewhere upwind of her (or a badly mismanaged outgrade pile if she is within range of farms) - also the configuration of the buildings around her garden could make a vortex or something that would operate as a kind of settling-pool for the spores. There are just too many variables to be sure...

As William of Occam said - "do not multiply causes" or in modern parlance keep it simple - especially true of the "first cause" because what happens afterwards is sooooo unpredictable.

Cheers.
With a microholding you always get too much or bugger-all. (I'm fed up calling it an allotment garden - it just encourages the tidy-police).

The simple/complex split is more & more important: Simple fertilisers Poor, complex ones Good. Simple (old) poisons predictable, others (new) the opposite.

leaningshed

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Re: preventing next years blight
« Reply #16 on: January 04, 2016, 12:54:11 »
Don't know if anyone has come across this before but James Wong advocates spraying tomato plants with aspirin to help with combating late blight - maybe worth a try?

The following is what he has to say on his web site:

Unbelievably, spraying a dilute solution of aspirin onto your tomato plants (we are talking half a soluble tablet per litre of water) is capable of causing their sugar content to soar one and a half times and boost their Vitamin C content 50%.
 
This treatment can even make your plants more resistant to cold, drought and (not that we'll ever need it in the UK) heat stress too. According to one trial this can even result in a 47% less incidence of late blight, the scourge of tomato growers,
 
This works as aspirin is a close chemical copy of the plant stress hormone, salicylic acid, which turns on the genes that regulate their defence systems.
 
The more stress a plant 'thinks' it is under, the more sugars are redirected to the developing fruit in a bid to make them irresistable to passing animals. Plants do this to ensure their seeds have the maximum chance of being dispersed to save the next generation, but it conveniently makes for tastier salad too!

 

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