Bordeaux Mix

[snuffer]

Hello all, I'm needing some advice. When should bordeaux mix be applied? After a smith period? During a smith period? or when one is expected?

In my area conditions have triggered a full criteria warning. If the same conditions apply tomorrow (and judging by the weather forecast it looks like they will) it will be a full smith period.

Should I spray my potatoes and tomatoes? HELP.

[Two_Sheds]

Current legislation still permits gardeners to use Bordeaux mixture and other traditional copper fungicides to control blight, but the use of copper in commercial pesticides is being reduced annually until withdrawal in 2008.

Products containing copper will be up for review on 31 Dec 2008 but according to DEFRA this could be brought forward if ‘earlier decisions are made or further prescribed extensions are granted’.
Gardeners can also use products containing mancozeb.
Both copper-based products and those containing mancozeb prevent the spores of late blight entering the leaf but do little to control the disease once established.

[Two_Sheds]

"To reduce the need to spray, forecasting the risk of attack has become very important.

In Britain the "temperature-humidity rule" ...is used. When Smith Periods occur, blight tends to develop 15 to 22 days later.
A date is set for the high risk periods and it varies for different regions. These "Beaumont periods" are announced on the radio to give growers time to spray their crops before the disease sets in. This reduces the amount of chemicals used as spraying is only necessary if an attack is imminent.

Clear as mud? Have a look here: Potato Blight - symptoms, causes and treatment

[Snadger]

It must be only certain areas that get blight? I've had my present allotment three years and never had it........neither has anyone else on the site as far as I know!

Wasn't it blight that caused the potato famine in Ireland where loads of people died?

Farmers and allotmenteers who grow spuds in areas prone to blight must be on tenderhooks when it is imminent!

[Flummery]

It was blight that caused the Irish famine Snadger, you're right. The main problem was that there were only a couple of varieties in common use there at the time. In South America where the spud originated, farmers will plant a field up with about 2 dozen varieties, then if some succumb to pestilence of any kind, they will still get a crop from the others. A lesson to us all about biodiversity.

Same thing happened with maize in the USA in the 70s. This is another reason for keeping some of the Heritage varieties in circulation. We never know when we will need their genetic input to breed disease resistance into our modern crops. Once it's gone, it's gone.

(Little personal rant over!)

[kernowyon]

sorry for being a bit dim, but what is a Smith period?

[mrswadders]

blight........

i've never heard any of these warnings, where did you here of them? Can anyone tellme if blight is forecast in northants as I lost most of my spuds and toms last year.........

[zanussi101]

On gardener's question time at the weekend, they talked about a testing kit for blight, see Welcome to Pocket Check
I don't know if it's worth the cost though....

[lumpyjumper]

I am in a full smith's period again down here (second in a fortnight) with the last 5 days meeting the weather criteria for a Smith's period.

If I get some bordeaux mixture do I spray it now, even though it will rain further and might wash off?

I lost all my tomatoes to blight last year so I've signed up to blightwatch this year and it emails me when we Smith's criteria is met.

[rogesse]

I'm dim too - what is a Smith period?

[terrier]

...and what are "Beaumont periods", please???

[SarzWix]

An explanation of 'Smith Periods' etc, plus signing up for Blightwatch alerts can be done here: Fight Against Blight 2008

[snuffer]

Hello again.

Thanks for the replies. Fortunately the smith period did not develop yesterday (to cold for the humudity levels). Follow Sarzwix's link to the blight watch site, that's where all the info. about blight and smith periods can be found. Whilst there sign up for the warning service, you don't have to be a commercial grower.

Just a little historical footnote. Blight caused the loss of the potatoe crop in Ireland but not the death of people through starvation. That was caused by wealthy greedy British landlords who continued to export other foodstuffs from their stolen Irish land instead of feeding the people.

[mrswadders]

cheers for the link. I've signed up, hopefully i can beat it this year - if only it would stop raining so that i can dig the spuds up!!!

[Paulottie]

It must be only certain areas that get blight? I've had my present allotment three years and never had it........neither has anyone else on the site as far as I know!

Wasn't it blight that caused the potato famine in Ireland where loads of people died?

Farmers and allotmenteers who grow spuds in areas prone to blight must be on tenderhooks when it is imminent!

Right on all three counts Snadger. Northeast rarely has problems....There has to be some good side to living in Geordieland

I've got over 150 potato plants and most are now showing signs of blight despite having sprayed. I don't hold out much hope for the maincrops...going to have to cut off haulms to try and stop it washing down. No sign on outdoor Toms yet...lost all but one Tomato last year.

The problem is that it has appeared so early down here the last couple of years...used to be august problem now appearing in June...I'm told there are a couple of different strains.