Full Smith Period warning

[vixylix]

Just received a full smith period warning for LS28:

There have been 2 days in LS28 where the Smith Criteria was met during the 14 days of data below.

1 Full Smith Periods were recorded.

My potatoes have been in since early April - I've left them in as they are still looking lush and green and lots of new leaves coming through... is it now better to be safe than sorry and pull them up before blight strikes?

Also - finally getting some little tomatoes through on my outdoor tom plants - is there a good way to protect them?

Wouldnt mind except it feels flipping freezing!!

[Nicos]

SK9 and WA15 have warnings too.

[Bill Door]

I've left them in as they are still looking lush and green and lots of new leaves coming through... is it now better to be safe than sorry and pull them up before blight strikes?

Personally i would say don't dig them yet. If you are worried and the potatoes have flowered then I would cut off the green growth to about an inch from the ground and leave the potatoes to grow and harden in the ground. I understand that it can take about 5 days for blight to appear after a Smith period. In that time conditions may have changed and blight does not occur.

Skip the tops if you think they have blight, otherwise bag them and leave them for 12 months them compost them.

Not sure about tomatoes. just keep checking them and if the fruit turns black then skip them and the potato tops.

Good Luck

Bill

[Thelma Sanders]

A Smith period only means the weather is right for blight, it doesn't mean you will certainly get it, if there is no blight in your area, then don't panic.

[Penellype]

I got a warning email too. I was out spraying my outdoor tomatoes with aspirin yesterday in the hope that it might help if blight is around. I've not done this before, but it is worth remembering that last year we had a full smith period 19-20 July and 5 full periods and 2 near misses in September, but my tomatoes didn't start to show signs of blight until October. It all depends whether there are any blight spores about, and as they are far too small to be seen it is impossible to know until signs of the disease appear.

If you notice signs of blight on potato foliage, the worst thing you can do is dig the potatoes up (unless you are going to eat them straight away), as this exposes the tubers to the spores which have fallen off the leaves onto the surface of the soil. Cut off the leaves at the first sign of blight, and leave the potatoes where they are for a couple of weeks before digging. It might not help, but its better than the alternative. For tomatoes, remove any fruit (including green) as soon as the tell-tale dark smudges appear on the stems. If you are lucky some of the fruit might turn red. If you leave it on the plant it will definitely rot.

[Potstubsdustbins]

If I am right one of the criteria for a Smith period is 90% relevant humidity I don't think I have ever registered that on my gauges. It's been in the high 70s occasionally but never 90%.

[Penellype]

You are correct with the 90%. Its been 100% here for most of the last 2 days. The current reading posted by York University weather data (it has finally stopped raining now) is 85.9%.

One thing to consider though is that the blight spores will have no knowledge of the relative humidity of the general area. The microclimate that they happen to be in is far more important. Therefore it may be 70% outside, but if the air around the leaves of your tomatoes has 90% humidity due to wet leaves or soil for example, that will be perfectly fine for the blight spores.

[Snow]

The weather is fairly pro blight at the moment and that is what the Smith period is confirming, but that doesn't mean there is blight.

I personally would not cut my plants back unless I actually see what might be blight or know that it is in the very local area.

[Potstubsdustbins]

I have two humidity monitors one in the GH and one outside. This was a pure accident as they are part of my radio frequency thermometer set up. I have fortunately never suffered with blight (famous last words) and never realised how useful they could be until I joined the vine.

[BUFFS]

If I am right one of the criteria for a Smith period is 90% relevant humidity I don't think I have ever registered that on my gauges. It's been in the high 70s occasionally but never 90%.

you could try living around here as its just stopped raining after about 3 days, non stop, water running down the inside of the greenhouse with the constant damp, my towel out there was wringing when I picked it up and that was under the staging, you could smell the damp and feel it on anything in there, I bet we get 70% in one of our "good" summers, good job we all know how to swim...

[SusieG]

Penellype - as a beginner, I'm new to this potato/Tom blight and didn't know what the Smith warning was!!!
Thanks for all the info!

[Nicos]

Maybe this forecast run of cold nights will hold it back a bit?

[Penellype]

I hope so Nicos, but it is a bit of a conundrum. We want temperatures of 10C+ for tomatoes, but less than 10C to guard against blight. Tricky.

[BUFFS]

Maybe this forecast run of cold nights will hold it back a bit?

we haven't started getting the "warm" nights yet, melons planted in march just gone onto the compost heap as only 12-14ins tall and nights getting colder..

[Penellype]

Don't say that! I'm trying to convince myself that there is still time for melons to ripen, if only the damn flowers would set fruit.