Blight — Katy in the garden

Sep 15

Sep 15 Blight

Tomatoes were one of the first vegetables I started growing and I suspect I’m not alone. Of the thousands who took up gardening for the first time during lockdown last year, I’m sure a large proportion found space for a tomato or two on their plot. Homegrown tomatoes are sensational. For the last two years, little Arthur (now 3) has loved the magic of picking baby tomatoes and popping them straight in his mouth. Very few ever reached the kitchen.

So last month, when I came outside one day to find large brown splodges on the leaves of all my plants, my heart broke. Not just for me, or for Arty (we’ve enjoyed tomato harvests before) but for all the first time growers out there who will have seen their healthy plants mysteriously collapse and their beautiful fruit, so close to maturity, fester and rot. Bloody blight.

The classic brown rot of blighted tomato fruit

Late blight, or Phytophthora infestans to be accurate, is a fungus like organism that affects many Solanum species, most notably tomatoes (Solanum lycopersicon) and potatoes (Solanum tuberosum) . Its sporangia (minute capsules full of spores) are carried through the air from plant to plant. In wet conditions (the spores literally have to swim to move around the plant), the spores infect plant tissue, multiply, and go on to release further sporangia into the air. And so blight spreads, from plant to plant, potato to tomato, allotment to back garden, a path of rotting destruction behind it. Still, it feels churlish to complain. The laments of today’s amateur growers is nothing relative to the horrors that blight has in its history.

Phytophora infestans was responsible for the deaths of over a million people in Ireland between 1846 and 1850 when it triggered the Great Potato Famine. Since its introduction in the mid 17th century, the Irish had come to rely on the potato as a means of growing high calories on poor soil. The Irish also relied almost exclusively one variety of potato ‘The Irish Lumper’ which had the strengths of growing well on infertile and waterlogged ground. Unfortunately this meant that there was almost none of the genetic diversity within the Irish crop which usually provides some protection to complete decimation by one disease.

Potato blight has shaped global history and culture. Not only did a large swathe of the Irish population die in the Great Famine, but it was also responsible for a mass exodus of a further 2 million or so Irish people in search of food and a means of supporting themselves between 1845 and 1855. These emigrants travelled in huge numbers to the rest of the UK, North America, Canada and even Australia changing the cultural landscape of the cities where they landed.

And it wasn’t just Ireland that suffered at the hands of blight. It devastated parts of America in the early 1840s before crossing to Belgium in a shipment of seed potatoes and wreaking havoc around Europe. During the First World War a late blight outbreak in Germany led to the death by starvation of 700,000 German civilians.

I suppose none of this helps me with my poor, rotting tomatoes, but I do find understanding blight’s history has helped me come to terms with my own, inconsequential loss. Blight continues to be a massive hurdle to feeding the population and websites such as BlightSpy or BlightWatch use information from professional growers to try to calculate periods of high risk. I’m not quite sure what good this does for amateur growers. In a wet summer it seems inevitable that blight will rear its ugly head and since chemicals that might help mass producers aren’t available (or really desirable!) to us, it’s easy to feel like a sitting duck.

Luckily there are a few things that can help.

First earlies - Tender skinned and early to mature

Potatoes

Plant First Earlies

Late blight only rears its ugly head from mid summer onwards and tends to affect Maincrop potatoes (often large varieties planted in early summer and taking some time to mature). So if you’re not hugely fussy about what type of potato you grow, choosing to grow all your potatoes in the spring (First earlies) is a good start. First earlies are young salad potatoes and mature quickly to be harvested from June. It’s a shame to limit yourself, and first earlies won’t store well, but they’re delicious and tender so it’s not a terrible trade off.

Earthing up

Potato tubers have a much better chance if the plants are well established before blight hits, so starting them in good time can help. Also earthing up (heaping mulch around the base of the plants) can help prevent blight spores reaching the tubers and buys you a bit more time. Once potato leaves show signs of blight, if you chop them all down and wait a few days you should find your potatoes untouched and good to eat in the ground.

Sarpo

There are a few really good blight resistant Maincrop potatoes, the most famous and successful of which are the Sarpo (pronounced Sharpo) varieties. These were developed by the Sarvari family for the Soviets who were looking for reliable, disease resistant, heavy cropping potatoes. Sarpo Mira and Sarpo Axona are the two best known and most widely available.

And for tomatoes…

Under Cover

Structures like a green house or poly tunnel can help keep blight away from tomatoes so if you can grow them indoors then do!

Keep them dry

Indoor tomatoes also do better because they aren’t rained on. Since blight needs water present to infect a plant, dry tomato plants in a greenhouse are often kept safe. Water tomatoes at their base rather than with a sprinkler to prevent splashing the leaves and creating damp conditions. Spacing the plants well and reducing overcrowded and lower leaves can also help to prevent the damp conditions that favour blight.

Start early

Blight is in the air from late June but only really takes off later in the summer. Sowing tomato seeds early gives plants a good chance of maturing before blight hits. Also, small cherry tomatoes ripen earlier so with these you have a better chance of getting at least some harvest.

Blight resistant varieties

Supposedly the varieties ‘Crimson Crush’, ‘Lizzano’ and ‘Mountain Magic’ are all blight resistant, so I’m adding these to my shopping list next year along with ‘Losetto’ and ‘Berry’.

It’s pretty disheartening to lose the lot this year when tomatoes have been such a precious part of our yearly cycle. Mind you, yesterday as I was walking through our neighbourhood I found a front garden full of cherry tomatoes untouched by blight only minutes away. So it just goes to show, some years you’re lucky and some years you’re not, but you should never stop trying!