Late Blight comes to Henfaes - very late

At last we have blight in our plots at Henfaes.  It usually arrives in late June or early July but this year the weather was unusually cold and it was dry here in June.  Temperatures went as low as 5C on several nights in June, July and August. It may be a low-temperature pathogen (stops growing over 25C) but growth is very slow at 5C.

Maris Peer was infected on stems as shown above. Quite often the node becomes infected as rain tends to lodge in the leaf axil.  But you can also see internode infection.  Multiple stem infections suggest that the mother seed tuber was carrying a latent infection from last year. The mycelium grows up the inside of the stem and erupts in places.  There was also quite a bit of stem apex infection as below.

Sometimes plots of Maris Peer resist infection as the variety carries the R1 and R2 resistance genes and if the gene products recognise the strain of blight then the big resistance guns are rolled out. Maris Peer obviously does not recognise this current strain of P. infestans.

Late blight comes to north Wales - late.

I can't remember when blight was this late showing its evil intent around here.  We have had quite a few Smith Periods of blight-conducive weather especially down on Pen Llŷn, the Llŷn Peninsula, where the humidity is higher and the nights warmer.  At Henfaes Research Centre on the north coast we have had cold nights, falling below 6C on several occasions recently.  This certainly slows the spread of the blight a lot. So it is not a big surprise that the first outbreak in north Wales is from Pen Llŷn.

I have been checking my normal hot spots - weedy crops and allotment sites where it usually turns up first but all crops have been healthy until now.  I guess there must be a lot more blight around now and it will show up and become widespread only too soon.  The Potato Council map shows the national picture.  It is obvious that few outbreaks of the disease have been noted (only 12 by the end of July) which is much like 2013 and a lot less than the average at this time of year.

I was hoping to assess our new blight-resistant tomato, Crimson Crush, but the plants I set out in the field are pathetic - they stopped growing and the foliage is showing the blue colour due to cold-induced potash deficiency.  I am hoping that the weather improves and the plants recover. However, fruit that was set before planting them out has ripened so it seems to be an early variety but not cold resistant!

Plant Sarpo varieties now

The trouble with second cropping is that the shoots emerge at a time when late blight is likely to be at its peak. But if varieties have useful resistance, they can struggle through a blight attack and give a good crop of new potatoes in late September/October.

Planting in large containers is a good idea as the plants can be moved to a sheltered location or into a cold greenhouse/polytunnel if the weather turns nasty or frosty.

Seed bought in the Spring for normal cropping can be kept through the early summer in trays or egg boxes exposed to the light.  You can keep them in a cool windowsill indoors or outdoors, again somewhere cool. Watch out for aphids on the sprouts and for hungry rodents.

Seed that is stored this way is physiologically old and that means the plants produced may lack vigour and have a shorter growth period before producing a crop of tubers. It means that maincrop varieties will form a crop within 100 days instead of the usual 120 or 130 days. You can read all about seed age in Steve Johnson's Bulletin (Univ. Maine).  He also explains how you can cut seed into pieces before planting.

I have been planting a batch of Sarpo varieties in containers periodically over the summer and am planting a new batch now.  I prefer to drop single seed tubers into small (1 litre) pots of compost just to start them off.  They should emerge from the compost in a couple of weeks when they can be moved to a larger container.  I use 35 litre pots and set two plants in each.  Plant fairly deeply to avoid greening of new potatoes that poke through the surface of the compost.
One litre pots with one seed potato in each

Repotting the rooted up seed into 35L pots. Dave here is a volunteer and great supporter of Sarvari Research Trust

Pots should be carefully watered - don't let the pots dry out and don't waterlog the compost or you will induce rots.

Experts like Dan Unsworth have refined pot-growing of spuds over the years.  His YouTube videos are really entertaining and show how you can produce very heavy yields of Sarpo potatoes using a variety of composts including his own from his compost heap. He gets 13.4lbs of spuds from a 35L pot in this video. I like his horse whinnying in the background of some of his films.

So far, so good. The Blight pathogen is slumbering

So far this has been a lousy summer - at least here in N. Wales. Yet there have been very few reports of blight in potato crops in UK.  So far, according to the Potato Council (now called AHDB Potatoes) website there is blight in 4 crops in Scotland, 4 in England and just 1 in Wales.  Undoubtedly, there must be more than this as lots of outbreaks remain unreported.

What is clear is that the amount of blight reported is a whole lot less than in any other year recently. Usually, by this time, blight has been seen most areas of the country and some crops are severely infected. Why can this be?

We certainly have had lots of dry weather that does not suit the pathogen and this has been combined with cold nights. Blight does not multiply and spread in these conditions.  However some districts have had Smith Periods (warm and moist), conducive to blight but the organism has not been around to take advantage and growers there have been lucky so far.

But we should not be complacent. We still have August and September left in the growing season and plenty of opportunity for blight to appear in force to cause havoc particularly in the maturing tubers. If the new potatoes get infected, they will not store and could start to rot soon after harvest. You can check on the incidence of blight in your area and the recent weather conditions here

A good method for controlling blight in a susceptible variety is to treat the crop with a liquid containing phosphite (phosphonate).  A product like Phi-Diamond produced by Emerald Crop Science showed good control when we used it in 2013. It controlled foliage blight and treated crops gave a good yield advantage. Phosphite is thought to act by stimulating the natural resistance mechanisms in the potato and is a benign chemical compared with other biocidal chemicals and a whole lot safer to use than the heavy metal poison that is copper.

The Taste of New Potatoes

It is that time of year again.  If you got off to a good start with your potato planting this spring, you should now have new potatoes waiting to be dug up and savoured. Do you think it worthwhile to grow earlies for a treat in June or do you think it a waste of time and space, maybe because you think new potatoes are not very special to eat?

I was reminded of the controversy over new potatoes after reading bits in the RHS journal THE GARDEN. One article was all about how the farmers of Jersey produce their winter/spring crops of Jersey Royals. A letter from a reader then responded and said that Jersey Royals no longer have a special flavour and challenged the growers to tell her why.

This opens a can of worms.  Let's get one thing straight first.  New potatoes as sold in the supermarkets are usually not that new.  They could be several months old and have been cold stored and maybe treated with CIPC to stop sprouting. The usual method is to grow an early variety until the little potatoes are the required size then to kill off the foliage with herbicide and leave the tubers to thicken their skins for 3 weeks before harvest.  These are not new potatoes and will not taste like new potatoes. At other times, the baby potatoes are graded from a mature crop.  The grader can take out the fraction 25 - 35mm and sell these smalls at an inflated price as baby potatoes.

But occasionally you see fresh potatoes with loose, flaky skins in the supermarkets.  Now these have been harvested by digging up green plants with a harvester (Greentops). The skins are soft and are partly removed by the machinery. The whole skin can be easily rubbed or scraped off (hence the term 'scrapers' to describe these). If they are boiled or steamed immediately, they could have a really special taste.  But often these loose-skinned potatoes don't get eaten for several days or even weeks and may be badly stored and may develop green chlorophyll just under the skin if exposed to light.  These are very unlikely to taste special.

Some varieties produce tasty new potatoes and other don't. Is there any truth in this?  Most growers agree that variety makes a difference.  In the olden days (when I was a boy) Ayrshire potatoes were touted as being super-delicious in June.  The variety favoured there was Epicure, a potato that matures to become quite floury.  The Irish still like the old variety, British Queen, that is also quite floury. Maris Peer is now a popular variety widely used to produce 'new potatoes' for supermarkets. New varieties are popular for a few years then are superceeded by yet newer ones. Some of the gardener's favourites are still grown in gardens up and down the country (e.g. Sharp's Express and Duke of York etc).  Some claim that the old French varieties like Ratte, Belle de Fontenay or BF15 are more tasty that home-bred varieties. I think some blind taste tests are warranted here.

And what about Jersey Royals? Well these are properly named 'International Kidney' and have been grown on the island for a very long time. International Kidney is a maincrop variety that has 'evolved' on Jersey to produce tasty earlies. This evolution is thought to be due to infection with a virus that changes the variety to one with earlier maturity.  When the variety is cleaned of its virus, it goes back to being a maincrop. Another fact about Jerseys is that farmers around the coastline that had access to large amounts of seaweed (kelp etc)  washed in by strorms naturally used this free fertilizers.  This probably yielded a spud with a superior flavour. I hear that few if any growers are still using seaweed as a fertilizer.  This alone might be why JRs do not taste as good these days as they used to do.

My recommendations for producing good flavour in earlies are:
Harvest while the potatoes are still small, scrape the skin off and boil/steam as soon as possible.
Let cooked potatoes cool as the flavour is at its best in warm not hot spuds.
Choose a variety known for its flavour. We think that Sarpo variety 'Kifli' is particularly tasty.
Experiment with the soil/compost you use e.g. add seaweed to one plot and keep a control plot without seaweed. And remember, you can plant early varieties from time to time until mid August and still get a useful crop of delicious new potatoes.  You can even take a maincrop variety like 'Sarpo Mira' or Sarpo 'Axona' and plant it in July to get proper new potatoes in September/October. Second cropping like this is best when a late-blight resister is used because susceptable varieties can often be blitzed as soon as they emerge from the soil.

HRH The Princess Royal came to see us today!

Anne, the Princess Royal, helicoptered in to Henfaes Research Centre today to talk to SRT and to agricultural researchers in the School of Environment Natural Resources and Geography (SENRGY). She was accompanied by The Lord Lieutenant for Gwynedd  the Vice Chancellor of Bangor University and The High Sheriff.

HRH was most interested in our work and admired our Sarpo varieties.  She accepted a sample of certified seed of Axona and Blue Danube.  She was particularly keen to try Blue Danube. Katherine Steele, SENRGY, told HRH about our collaborative work with Burpee on late-blight resistance in tomatoes

Guests included representatives of the Welsh Government, DEFRA, NERC and Snowdonia National Park.

I was too busy to take photos except the ones below.
Helicopter circles the farm


Welsh Government Minister visits the Trust

@WG_FinanceMin ister and Leader of the Assembly, Jane Hutt, came to Henfaes Research Centre on Thursday with the CE of WEFO (Welsh European Funding Office) to find out how KESS (Knowledge, Economy Skills Studentships) have benefitted SRT and Bangor University. 

Our students, James Stroud and Natalie Chivers, told her about their projects. James said how he had used molecular markers to identify late-blight resistance genes in tomato and different strains of Phytophthora infestans. Collaboration with Burpee Europe and Dr Katherine Steele, Bangor University, has culminated in the selection of a new cultivar of tomato, Crimson Crush, with excellent blight resistance for outdoor growing in UK. Natalie explained how her project will find out how far fields of flowering potatoes benefit pollinating and predatory insects. Another KESS studentship to Simon White is using molecular probes to identify blight resistance genes that can be bred into new Sarpo potato varieties.

Guests were pleased to receive gifts of certified seed potatoes resistant to blight. The Minister said she would give some to her colleague, Deputy Minister for Food and Farming, Rebecca Evans AM

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L to R: Damian O'Brien (CE WEFO); David Shaw (SRT) Minister Jane Hutt, Natalie Chivers; James Stroud and Katherine Steele.

James and Natalie with posters