[mumofstig]

Bayer Garden Fruit & Vegetable Disease Control or  Bordeaux Mixture.

[Baldy]

Thanks JayG - I've decided to zap the foliage - haven't got time/space to sort out storage if I pull them up - and there are only so many potato based meals my family will put up with...
One Tom had a couple of low level leaves that looked suspicious - I rather suspect that the plot toms. are done for...

Cheers,
Balders

[Martifromduram]

Didn't look like magnesium to me, strip out and monitor new growth, magnesium will only appear in new growth as it is an immobile nutrient.

[Salmo]

Didn't look like magnesium to me, strip out and monitor new growth, magnesium will only appear in new growth as it is an immobile nutrient.

Magnesium is mobile in the plant but immobile in the soil.

That is why when treating deficiency symptoms in the leaves it is best to spray the leaves with Epsom salts (magnesium sulphate) rather than applying it to the soil.

Magnesium deficiency always shows first in the older leaves. Because it is mobile in the plant, when there is a shortage the plant is able to transport it to the all important new growth which keeps it green and growing strongly.

High levels of potash can reduce the uptake of magnesium and although it may not be short the deficiency symptoms show up.

Most of the "old leaves" on tomatoes show severe magnesium deficiency, probably due to the high potash fertilizer which it is normat to apply e.g.tomorite.