Topic: There IS life after potato blight strikes

[Kepouros]

In thread after thread I have noticed that people who ask advice when blight strikes are advised to chop down the haulm immediately and save what crop there is, and there are horror stories about blight turning the potato plants into a black rotten mass virtually overnight.

This advice usually results in many potential crops simply being wasted, when much can, in fact, be done to preserve the plants long enough for a reasonable crop to be obtained.

Blight struck my King Edward (maincrop) potatoes 2 weeks ago today.  They will not, of course, produce ANY potatoes for several weeks yet so it would be simply a waste to cut them down.

These are those same plants today





I have so far removed about 30% of the foliage to clean up the plants and sprayed again. You can see that despite the loss of foliage the plants are relatively healthy, and have no stem lesions or rotting stems. A few more blight spots appear on the leaves every day, and these leaves are removed promptly, but at the same time the plants are still growing and will continue to do so, despite regular foliage removal, for several more weeks at the current rate.

This is a practice I have used for several years. I have never lost a crop and I have never yet had a potato rot in storage through blight.

Commercial growers do not, of course, remove affected leaves, but nevertheless usually keep their plants, spraying regularly, until foliar loss approaches 80% before they burn off the haulm with sulphuric acid.

[tim]

Same as I do with Tomatoes.

[Frantic-gardener]

    Hello,  I have a plot on an allotment in South Devon,  (Teignmouth)   All the plot holders here have tomatoe blight.   A lot of the others have sprayed with Bordaux mixture, are there any alternatives to spraying, given that the weather is still very wet down here.  Even on dry days we still have very high humidity. 
I am toying with the idea of re-sowing seeds, as even the plants offered by our local garden center are showing signs of blight.
Thankfully, my potatoe crop is fine and showing no signs of problems.
I would be gratefull for any thoughts or suggestions.

[Mrs Ava]

I reduce the speed of blight attack by growing my tomatos under a roof.  I have a wooden structure, bascially like a pergolla that runs the width of my plot, and is about 6 or 7 foot wide.  On the top I have corrugated plastic sheets.  The plants are then grown under this roof.  This does 3 things, stops the plants getting wet when it rains so the plants are dry and in theory, the blight spored carried in the rain don't land on my plants, slightly reduces the temperature so the toms ripen just a little quicker than those grown outside, and thirdly, gives me another roof from which to collect rain water.  ;D  I believe I saw Bob Flowerdew and an Italian allotmenteer growing toms like this.  If the plants do get struck by blight, it is usually very very late in the season, by which time I have harvested masses of toms and I really don't care by then.  I do spray with bordeaux a couple of times during the peak. but last year I was the only person on our allotment with toms, everyones were wiped out in early July, I was still harvesting in October!

[ruud]

That is the only right thing to do e.j.Tommies dont like water from above,and if it is that the leaves are wet they have to dry .So a roof above there heads is the only right thing to have healthy toms.

[Svengali]

My blight appeared almost overnight, but with constant, torrential rain, there was not much I could do about it. About a week after it appeared, I sprayed with Dithane. I have now had it for about two weeks.
Most of my plants are yellow, some still green. These are second earlys, and I have dug a couple of plants, and found a reasonably good crop.
As I would normally start to dig these spuds now, am I best served by digging all, and hoping they will keep, clearing all the foliage, and digging as required. Leave the foliage on, and hoping?
The weather is fine & dry today, and as I have very sandy soil, digging will not be a problem - but nor would wash-down from the diseased plants.

[Kepouros]

Most of the second earlies are now pretty near maturity, and the yellowing plants suggest that in the case of your own spuds.  If you feel that the satisfactory yield you have had from the two plants you dug is likely to be indicative of the rest of the crop then I would cut down the worst affected ones.

However, it would not be wise to start digging yet.  If you wish to store the harvest for any length of time the tubers need at least a fortnight underground for the skins to set, and you also need to wait 2 - 3 weeks from the time the haulm is cut to allow the blight spores on the soil surface to die off.  If you dig while there still live spores on the soil surface you almost certain that at least some of the tubers will come into contact with them, with the probability of rotting in storage.

 To avoid any mix-up about which tops were cut and when it would certainly be simpler if all the haulms were cut at the same time.  However, if you are confident that the still green plants have a reasonable amount of clean foliage and untainted stems, then by all means give them a bit longer and increase your crop, but keep on removing all infected foliage as it occurs.

[Svengali]

Thanks for that. If the rain holds off again tomorrow, I will start cutting.