[surbie100]

My local weather forecast looks like I will have the first full Smith Period in my area covering Fri & Sat. The FAQ on here only talks about spraying and I do have Bordeaux mix as a back-up but I'd rather avoid using it if I can. (the toms and cape gooseberries are all ripening now)

Will covering plants give my crops an adequate level of protection?

For me this means covering potatoes with clear plastic sheeting (I have lots), taking cape gooseberries & aubergines into the shed for a couple of days and shutting up my plastic growhouses which have the tomatoes in.

Does anyone know how long after the Full Smith the blight spores can last?

Thank you for any help! 

[Nikkithefoot]

A full Smith Period only means that the conditions for blight propagation are exactly right. It does not mean you are going to get it.

Covering with anything that is going to increase the relative humidity in a local area would in my opinion increase the chances of blight rather than prevent it.

Blight is caused by fungal spores, and fungi of all descriptions love warm humid (damp) conditions. Dry airy conditions will cause them to desiccate and die.



 

[JayG]

For the plants to actually succumb to blight, any spores which land on the leaves have to germinate, which requires conditions of warmth and high humidity (hence the "Smith's periods")

It's therefore important to avoid doing anything which will create a microclimate which actually creates those conditions accidentally, so covering with plastic sheet is a bad idea.

Unnecessary wetting of the leaves is therefore also to be avoided, and under cover I try to make sure ventilation is as good as it can be. I take special care to remove leaves growing squashed up against the greenhouse glass where they can trap condensation and stay wet nearly all day long.

The rest is down to chance, in particular whether there are actually any spores around to germinate - the risk tends to increase as the summer progresses; last year was terrible, this year is not bad so far apart from outbreaks in a few areas of the country.

[goodtogrow]

In the past I've dug up tomato plants on the allotment and hung them in the garage for the fruit/berries to ripen.

Fruit which had already turned yellow went on to ripen.  Green ones didn't.

Does anyone else do this, or is it me just being kooky?

Tom

[mumofstig]

A full smith doesn't mean there is blight in the air, just that conditions are right for it to grow, if it is.

Have you got blight near you, that you suspect it is in the air? look at the Blight Map
http://www.potato.org.uk/fight-against-blight/blight-incidents

If you can cover plants with polythene it will protect them a lot, but is not fail safe as it's possible to get blight in polytunnels and greenhouses if it blows in through open doors and vents.

there doesn't seem to be any info about spores in the air, but spores on the soil surface are presumed dead after 2 weeks.

[JayG]

You haven't said whether yours were healthy or blighted plants Goodtogrow. 

If blighted, as far as I know blight starts on the leaves or stems and then moves to the fruits, so I would be wary about trying to ripen them whilst still on the blighted plants, and there is also the risk of adding more spores to you local environment.

Hanging up healthy plants no doubt works OK, although I personally ripen mine in a dish on the kitchen windowsill - sometimes up to 2-3 deep but examining and turning regularly, especially if there are blight suspects in amongst them. I believe the ripening fruits produce ethylene which helps the others to ripen if they are at close quarters, which probably wouldn't apply so much if still attached to the plant in a garage.

[goodtogrow]

They were healthy plants, JayG - I give up on blighted ones.

Agree with the ethylene thing - they say add apples for the same reason - but that must apply to hanging trusses too.

Used to get more success hanging on the plants than off the plants, believing that the dying plant in some way provokes ripening, but I don't profess to understand the science.  There's a parallel with ripening onions, and not removing the stems after digging up.

All of which is very academic 'cos I don't grow toms anymore on account of the regular, and early, blights.  I just don't appreciate Nature's sense of humour, waiting until the toms are almost ready, then killing them!

Best wishes

Tom

[surbie100]

The nearest red dot on the blight maps is 20 miles away, so though it's down as a very severe case, I think I am currently ok.

But my site is by all accounts very blight-prone. If there's a Full Smith, I've been told it's very likely we will get it, and spraying after you get it is obviously too late. I lost all my tomatoes to blight last year.

Given what you've said, the growhouses are drying out today and I'll shut them up tonight pre-rain  - the potatoes will take their chances rather than being covered and I'll think about whether to spray on Sunday.

Thanks all. 

[Salmo]

At this stage of the season I would be inclined to cut the tops off potatoes at the first signs of any blight. They will have bulked up by now and will stay safely in the ground for a few weeks.

Tomatoes are a bigger problem. The only way to protect them is with sprays of either bordeaux mix or Bayers Fr & Veg fungicide.

There is no pre-harvest interval on either packet but I understand that bordeaux is 1 day, but wash them.

[seaside]

This is the help you really want Surbie... don't panic. Look at the weather forecast and look at what is happening next week for most of us.
Blight even now still hasn't really got a head of steam up yet, and I firmly believe there is a cumulative damp effect within the blight spore population and how quickly it spreads. We've had a fine Summer so far, and  this next couple of days is the last wet murk for a little while. Summer is returning next week ... hold your nerve. Trust to providence ... don't join the doom mongers and sprayers. You know you don't want to really

[surbie100]

This is the help you really want Surbie... don't panic.

  I am something of a worrywort!

The forecast has completely changed now so I do feel something of a numpty for getting so het up about it. Mebbe when I've got more than 1 year's growing experience...!! 

I hope your second Summer prediction comes true Seaside.