I noticed today that the lower leaves of most of my Pink Fir Apples
potatoes are turning yellowish, and some with black spots.

Is it to early for blight? Last year all our tomatoes succumbed to
blight but I seem to remember that it was later in the summer. I'll be
very unhappy if it is blight, as I have about 160 potato plants in,
and I can't bear the thought of losing them all.

It's my first year of growing potatoes so I'm not sure what's
happening. Any advice would be very welcome.

Will

In article , will
writes
I noticed today that the lower leaves of most of my Pink Fir Apples
potatoes are turning yellowish, and some with black spots.

Is it to early for blight? Last year all our tomatoes succumbed to
blight but I seem to remember that it was later in the summer. I'll be
very unhappy if it is blight, as I have about 160 potato plants in,
and I can't bear the thought of losing them all.

It's my first year of growing potatoes so I'm not sure what's
happening. Any advice would be very welcome.

I'm afraid that it does sound like blight, the microscopic fungal
disease phytophtora infestans - that can occur at any time of the
growing season. Get a second opinion on it fairly quickly and if blight
is confirmed, bite the bullet and have the lot out immediately. Blight
is a contagious disease, the spores of which can live in the soil, so it
is possible that the infection has been transferred from your last
year's tomato problem. If there are any unaffected tubers, you could
consider those to be edible, but all rotten tubers and the haulms should
be incinerated. The soil where they grew should not be used for any
member of the solanum family (potato, tomato, capsicum, aubergine, cape
gooseberry etc.) for 3-4 years. It can be used for other plant families,
but it would be better left to fallow for this summer, then a green
manure sown in it and turned in at autumn time. It would then be ready
for planting next spring.

Bordeaux mixture is sometimes used to tackle potato blight. It does the
job of stopping disease spreading in the plants very effectively, but it
cannot cure already rotted tubers and it leaves fungal spores to re-
infect other crops. It can also leave copper based anti-fungicidal
residues on tubers to be eaten. For those reasons, it is not recommended
for use on growing crops in organic systems.
--
Alan & Joan Gould - North Lincs.