Blight Alert already

[seasprout]

Sorry to be the bringer of naff news, I’ve just received this morning a blight alert e-mail.

I’m in the East Mids and conditions are right for blight.

I’ve swam to the greenhouse and everything looks ok so far.

Keep an eye on your crops peeps.

[Cadalot]

I've not even got my tomatoes to a size they can go out yet !

[Martin H]

I just checked ... my area met the Hutton Criteria twice this week, on Monday and Thursday. Fingers crossed it dries up soon!

For those who've lost the Blightwatch link, it's here: https://blightwatch.co.uk/amateur/

[Penellype]

A couple of years ago the criteria for a blight alert were changed from a Smith period to Hutton criteria. The difference is in the number of hours of humidity above 90% required for an alert.

Smith period: 2 consecutive days with minimum temperature above 10C and 11 hours of 90% humidity.
Hutton criteria: 2 consecutive days with minimum temperature above 10C and 6 hours of 90% humidity.

It doesn't take a genius to work out that the Hutton criteria are going to result in vastly more alerts than the Smith periods.

Having said that, the past week's cold wet weather has resulted in extremely humid conditions most of the time. Therefore those of us who have been "lucky" enough to have night time temperatures hovering around 11C (there is very little variation between day and night temperatures when there is a thick blanket of cloud) will easily meet the 6 hours Hutton humidity criteria and probably the 11 hours Smith criteria too. In my untrained opinion the Hutton criteria are going to result in blight alerts almost every time it rains, and certainly in every warm (and humid) sector of a low pressure system. We didn't get them until later on last year only because it was very dry. If you think about it, what the Hutton criteria are saying is if its warm enough for tomatoes and in any way humid, the conditions are suitable for blight - we have been "saved" from a 3 day Smith period here only by a minimum temperature of 9.9C on the night of the 12th, which illustrates that you need to regard any criteria with a hard barrier as not set in stone.

Don't panic. In order for plants to get blight there has to be blight spores around in the area. Use the alerts to warn you of the possibility of blight and keep more of an eye on things than normal. Remember that it can take a week or 2 for the symptoms to appear after the plant is infected - the worst situation is 2 Hutton periods about 2 weeks apart as this helps any infection to spread. But just because you have had an alert it doesn't mean you will definitely get blight.

There is a map of reported blight incidents here: https://blight.ahdb.org.uk/BlightReport. As with most of these things, they have "improved" it and made it harder to use. If you click on an incident you get more details and if you look at grid mode you get a list of incidents, but with the useful postcode info removed so from the list you have no idea where they are (you can find out the post code by clicking through the individual incidents on the list, which is tedious). The map does give you an idea of where the blight has been found though, which is very useful.

[ameno]

Isn't it a bit early for blight? Even if the climate conditions are right for it, if there are no spores about yet to spread it then nothing can catch it. It doesn't just appear out of nowhere, after all. And it also can't overwinter as spores, only as a living pathogen on a plant, usually potatoes. So that first overwintered generation needs to mature and spawn before any fresh plants this year can catch it

[veggiechicken]

Blight warning today here in South Wales too.

[treepixie]

And one in Reading also this morning

[bramble]

Blight warning here today as well.

[Martin H]

Isn't it a bit early for blight? Even if the climate conditions are right for it, if there are no spores about yet to spread it then nothing can catch it. It doesn't just appear out of nowhere, after all. And it also can't overwinter as spores, only as a living pathogen on a plant, usually potatoes. So that first overwintered generation needs to mature and spawn before any fresh plants this year can catch it

In the East of England (my area) there are only 2 confirmed blight outbreaks as of now, one near Margate and one near Lowestoft, both in outgrade piles. I don't understand why potato farmers can't find a more sanitary way of disposing of outgrade potatoes, but there it is. There's another unconfirmed report near Ipswich. With any luck we'll keep westerly breezes for a while, to keep the spores away from my garden!

[geepee]

Blightwatch warning this morning here .
Gp

[Penellype]

Blightwatch warning this morning here .
Gp

That's really interesting - we have nothing in York as both the minimum temperature and humidity hours are below the trigger levels. I thought Harrogate was colder than York!

[toomanytommytoes]

No blight here yet, but some of my potatoes look to have septoria leaf spot.

[hamamelis]

Isn't it a bit early for blight? Even if the climate conditions are right for it, if there are no spores about yet to spread it then nothing can catch it. It doesn't just appear out of nowhere, after all. And it also can't overwinter as spores, only as a living pathogen on a plant, usually potatoes. So that first overwintered generation needs to mature and spawn before any fresh plants this year can catch it

Sadly, no.

Long story short, blight is native to South America. When it first showed up in Europe, almost certainly on some imported potatoes, only one 'mating type' was brought over.

Blight needs two mating types to mate, so this meant it could only clone itself. It was extremely good at spreading and killing plants with no resistance, so caused huge famines, but it could only clone itself. This meant it changed very slowly, if at all, was dead predictable and could only survive on living plant material. Plant breeders could keep ahead of it without too much trouble.

Unfortunately, in the mid '80s, (probably, it took a while for it to spread and for anyone to work out what had happened), someone accidentally imported potatoes infected with the other mating type to Europe. This second type has now spread basically everywhere, and blight is now able to get jiggy, after over a century of celibacy.

This means that blight's getting less predictable, and is evolving far faster than it used to. This is part of the reason the criteria got changed to be less strict; an increasing number of outbreaks occurred in periods that wouldn't meet the Smith Period criteria.

Blight's being a problem further North than ever before, resisting pesticides faster, overcoming variety resistance and other fun changes. Being able to mate also means it can produce a different kind of spore- one that can actually overwinter in soil and infect plants really early in the season. No-one's quite sure how long they can survive as 'oospores' (as they're called) and still infect a new host, but it's thought to be about 4 years.

If you think blight's more of an issue than it was when you were younger, you ain't wrong. It's not getting much attention outside of scientific literature, but blight is probably going to be more and more of a problem every year, unless we somehow find a way to get rid of it for good.

Guess what I wrote an essay on a few months ago.

[Matt94]

Have any of you used a baking soda spray to prevent/ reduce the spread of blight?

https://migardener.com/prevent-kill-...w-baking-soda/

[toomanytommytoes]

I've used potassium bicarbonate to stop powdery mildew with success. Prefer it over baking soda (sodium bicarbonate) to reduce the risk of sodium building up in the soil.