Thursday, 22 July 2010

Blight is Busting Out All Over

The recent prolonged spell of wet weather has meant that potato blight has devastated our potatoes and outdoor tomatoes. Again. It's singularly dispiriting to look at the mark of the beast all over that formerly healthy foliage and it's hard not to feel that some sort of divine retribution is involved. Since this picture was taken, things have got a whole lot worse. I could wax lyrical about suppurating sores, expanding lesions and stem collapse, but I'll spare you the gory details.

Cornwall does seem to be an evolving centre for Phytophthora diversity - I suppose our moist, mild and humid climate is responsible for that. Potato blight (Phytophthora infestans) has been around for a long time, although it has recently undergone rapid evolution due to the rampant coupling of the original A1 strain with A2, which arrived in 1978. This unholy union produces oodles of oospores, the tough walled, overwintering products of sexual reproduction. These germinate to give all sorts of charming new variants, ready to attack previously "blight resistant" varieties. I'm hoping that Tom Wagner and his worldwide web of collaborators will be able to develop some new varieties of both potatoes and tomatoes to deal with this challenge.

We also have Phytophthora ramorum, the ominously-named Sudden Oak Death, which, ironically, has mainly been killing rhododendrons. Lately it has jumped hosts and is now attacking Japanese larch (Larix kaempferi), an important forestry tree hereabouts. On a recent train ride along the edge of Bodmin Moor, I could easily see the damage - trees with brown crowns, releasing millions of highly infective spores. Some 250 hectares of Japanese larch are due to be felled in this region, in an attempt to contain the spread of the disease. If it's anything like potato blight, I expect that it's already too late. And let's not forget - we have our very own Cornish Phytophthora - P. kernoviae, first described from the Truro area in 2003. Its favorite host is, at present, the rhododendron, which is plentiful, in both the wild form (Rhododendron ponticum) and numerous ornamental varieties. It also likes beech and magnolias. Owners of historic Cornish gardens must be quaking in their boots.

The Peruvian Purple potatoes were the first to go - we'll lift them a bit later. I was more interested in trying Rote Emma. This is a pink-skinned, pink fleshed variety that was given to me by Ulrike Paradine. I know very little about it, other than it tastes delicious. Unfortunately the slugs seem to agree, so an early harvest might not be such a bad thing. Thanks, Phytophthora.

Here are some Rote Emmas fresh out of the ground. Blight-blasted foliage removed for the sake of propriety.










Here they are after a bit of a wash, with a cut tuber to show the flesh colour. I expect they're full of healthy antioxidants.














And last but not least, boiled, with a pat of artery-clogging Cornish butter. Comfort eating at a time of crisis.

6 comments:

Robert said...

According to an article in 'Organic Way', which I recieved yesterday, 90% of the blight currently in Britain is a mutated strain called 'Blue 13'.

It appeared in 2005, it's more virulent than earlier strains, and it attacks a lot of the varieties which had some resistance to earlier strains. If this is right, it explains why the diease has become so virulent over the last few years.

IAP said...

A sad sight. It makes me slightly more grateful for our drought-stricken conditions here in the south-east. Still no sign of blight (or rain).
Maybe you could cheer us all up by writing some fiction - a post about Sudden Couchgrass Death, and Bindweed blight for example.

Nice-looking potatoes tho'.

Jeremy said...

Do you remember that idea about inserting a copper wire through the stem of the plant, in advance of blight? Maybe next year you could do that. Unless, of course, you're worried about the traces of copper.

orrflo said...

Sorry to read you have some much problems with phytophtora, it can really have an enormous impact on harvests of tomatoes and potatoes. Over here it has been so amazingly dry, no blight, but this drought did have other consequences: I lost about 80% of my mashuas and perhaps more of the ullucus, I must check the ocas, I let them be overgrown by weeds, so damage is not that big (at a first glance it seems to be less).
There seem to be quite a lot of phytophtora infestans strains, there is a completely other one in the US/Canada, who is said to be more devastating (if that's possible..) compared to the strains in Europe. As far as I have read the latest reports, we only have the A1 over here, but these things can move very quickly, and if it starts raining we'll see what happens. Some potatoes didn't even start growing because of this drought, I still have 'early' Doré potatoes that should start growing. The Andigenum tubers did grow a lot better compared to other (European bred) potatoes, they were vigourous and flowered happily.
I tried the copper-wire method many times, but results were just no good, plants did get the blight as quickly as non-copper-wired plants.

Hannah said...

Awww so sorry to hear about your crops. How disappointing. The blightwatch website keeps telling me it's in my area but so far we seem ok.
The red potatoes look absolutely fantastic.

Rhizowen said...

Hi robert

Blue13 is also metalaxyl resistant - it's a nasty blighter - literally.

IAP - bindweed blight - now that would be useful.

Jeremy - for some reason I've never got round to trying that. Perhaps next year. I t would probably help to repel slugs too. Alternatively I could just go up the road to some of the old copper mines and collect material from the spoil heaps and dust the foliage. The combination of copper and arsenic might do the trick.

Hi Frank
I'm beginning to realise that our respective climates are quite different. Hope you get some rain soon (but not too much).

Hi Hannah
Hope your garden escapes the blight for a while longer. There's nothing quite like it to ruin a stroll round the garden.

Related Posts with Thumbnails