Topic: Tomato blight and potatoes

[stevic]

Hi all, this is my first post, so let's get down to the nitty gritty.

Last year on the allotment three of the four types of tomatoes I grew outdoors were affected by blight, these were Super Marmande (badly affected), Ailsa Craig (pretty badly affected) and Golden Sunrise (hardly affected), the Gardeners Delight were not affected at all, they were grown in a different part of the plot.  Several of my fellow allotmenters suffered the same problem, some lost all their tomato crop.

This is where I need some advice; I was preparing some trenches for potatoes today at the spot where last seasons infected tomatoes had been growing.  I have dug in a load of compost, but a thought has just crossed my mind: it may not be such a good idea to grow spuds where there was a crop of blight infected tomatoes growing last year.

Question one: what is the liklihood of the potatoes being infected by blight?

Question two: if there is a liklihood of infection, what should I grow on this part of the allotment?

All the infected plants were burnt last season.

I'm pretty new to this allotment game and last year was my first season, so please keep any answers really simple ('cos I am  :)) and I await your expert answers.

[katynewbie]

???

Am by no means an expert, and know very little, but think that there is a problem with spuds and toms and the same diseases. So I agree...stop right there!!

An expert will be along in a minute to give all the proper answers!!

 ;)

[Merry Tiller]

Blight is an airborne disease, if it's about you'll get it wherever you plant your spuds

[philcooper]

It is the same disease, Phytopthera infestans, (it translates as infectious plant killer).

It requires live plant material on which to live.

So if you removed and burnt all the infected material - 10 out of 10!!

It is not a good idea to grow plants of the same family (and spuds and toms are both in the same family - hence their susceptibility to the same disease) in the same place year on year so if you can plant the spuds somewhere else. If this is not possible they do not share too many of the same diseases and, as I said the blight will have gone away by now.

Blight is a fungus and is spread by spores in the wind or by aphids which have fed on diseased plants (and are then blown by the wind)

If you do get blight on spuds or toms, cut the foliage down immediately, remove and burn it.

That will take care of the toms but the spuds, if for storage should not be lifted for 3 weeks. This allows any spores on the surface to die, otherwise there is a dager of the spores getting onto the tubers and causing tuber blight - not nice

Regards

Phil

[Robert_Brenchley]

I got blight on my toms last year, but it didn't affect the spuds for some reason. Maybe the toms were more susceptible. I'm growing them in different places this year and hoping to avoid a recurrence.

[Motherwoman]

The earlier you grow your spuds the less chance of getting blight and if you can construct a sort of half poly-tunnel over your toms on the windward side you can delay the arrival of blight spores on your toms.The best variety I had last year was a heritage variety called Spanish Globe and I had one Roma survive with no blight at all when the others all went down,I saved the seed and will see how they get on this year.

[Busby]

My suggestion Stevic, would be that you make a plan every year of what was grown on each bed and just don't grow the same thing on the same spot for another three years. Except tomatoes - they can be grown on the same spot for years but it does help to add fresh earth each spring. Tomatoes musn't be near potatoes and you cannot plant potatoes where tomatoes were.

I have discovered that certain kinds of tomatoes are pretty resistant to blight, whether in a greenhouse or outside. So it's best to make a note of each sort. A friend of mine has just told me that if you line the tomato trench with stinging nettles all blight can be avoided - something which I am going to try.

You will also need to disinfect tomato poles and sticks before using the the next time - the best way to do this is to leave them outside for a few weeks in late winter.

[Robert_Brenchley]

I'm growing nine different varieties this year and it's going to be interesting to see what happens if I do get blight. They're going to be all over the place though, wherever I can squeeze a few in, so I'm not sure plastic covers are going to work. I'll try though. This is where we need a forum like this; with all the emphasis on greenhouse toms, there probably hasn't been much effort put into find which varieties will actually withstand disease outside.

[Merry Tiller]

Tried Ferline?

[Robert_Brenchley]

No, but as long as it's not an F1 it might be one to try next year.

[stevic]

Thanks for the replies.  There are some points made that are most interesting.  The Gardeners Delight were not infected with blight probably because they were upwind (prevailing wind direction) of the spuds, the other three varieties being downwind from the said spuds.

[Merry Tiller]

No, but as long as it's not an F1 it might be one to try next year.

I'm afraid it is indeed an F1, but it stands up to blight for weeks longer than anything else I've tried

[Robert_Brenchley]

I had a feeling it was. There must be normal varieties out there that will stand it.

[misterphil]

1 quick comment - try spraying with bordeaux mixture (allowed organically, apparently) before, during and after the blight season.

2) I'll post next week when I go back to school re an alert service for blight conditions from the potato growers association. Blight occurs in high moisture/heat conditions, and they monitor conditions across the country and email allerts ... but to my school email, which I can't access at home...

Cheers

Dave

[cliff_the_gardener]

Stevic,
A lot of good advice on avoiding blight.
Two points to highlight -
1.  Crop rotation spuds and toms are same family so fit into the same part of your rotation.
2.  Blight is an airborne fungal disease.  Removal and distruction infected material is impotant.  If diseased material is left on the ground then the spores will germinate next year and infect via water splash.

Be watchful, and act when you see signs on either Potatoes or Toms.  Also remember that there are two types of blight - late (the irish famine) and early blight.  Early is less of a problem but can affect outdoor toms and knock them.
If you are organic then Boreaux mixture, if not Dithane 945

Clifford

[Robert_Brenchley]

The first year I had my plot I had an outbreak of early blight; I lost all my spuds and my toms. It may not be so prevalent, but it's just as devastating when it hits, and because it's early, there's little chance of salvaging anything at all.

[cliff_the_gardener]

Unusual for early blight to kill off spuds - the tops may be affected but tubers are out the ground and eaten whereas late blight makes the tubers rotten on storage.

[philcooper]

Early and Late Blight are US terms

Early blight, Alternaria solani is not common in the UK.

We have Late Blight, Phytphera infestans, which can come early in the season!

Plants can survive EB but not LB, the 2 pictures below of the left show EB on tomatoes and the (black) marks on potato leaves,


The picture on the right shows the early symptons of LB on potato leaves (brown); tomato foliage, stems and fruit go black and die within a couple of days.

The damage to potato haulms is known as leaf blight. If the spores of LB get on to tubers then this can result in tuber blight, this is what makes the tubers rot.

So if you see leaf blight symptoms, cut off the effected foliage and burn it.

If you intend to store the potatoes, do not lift them for 3 weeks, this allows any LB spores that may be on the soil surface to die (they can't live without a live plant host). If you are not going to store the spuds, you don't need to worry.

To reduce the risk of LB, spray with a Bordeaux Mixture liquid every fortnight (or after rain) when you know that there is a risk of LB

Phil

[cliff_the_gardener]

Sorry to differ Phil, but Early blight is more of a problem now - I have had it identified on my potatoes by RHS Wisley.
Two years ago most of my earlies were hit - I didn't understand why - so sent samples off.

[philcooper]

Cliff,

Sorry Cliff, you are right EB, is common but, until global warming heats us up a bit more it is of "Little economic importance under UK conditions" quote from the British Potato Council, it advises no specific action to be taken (does the RHS differ?).

Late blight, which, as I said, can come early (July onwards) is the one to watch for and causes what is commonly know as leaf blight and is treated by removal of the haulms.

It also causes tuber blight if the spores get onto the tubers, either by digging up the tubers whilst there are still spores around or, in very wet condition, by the spores being washed down the stems and onto the tubers.

Phil