this is blight isn't it - help!!!

[newboy74]

Please help!!!! - hope you can see the pictures.

The black spot looks very much like blight to me - is it? Its on a Main crop Desiree plant.
Most of my other plants are carlingford second earlies which have flowered and a few leaves have turned yellow but no black spots.

I plan to cut all the green down to ground level and leave the potatoes in the earth to harden for a week - is this advisable?

please help!

[Two_Sheds]

http://www.growfruitandveg.co.uk/gra...ght_33866.html

That's one we made earlier

[rustylady]

That spot doesn't look black to me. Is it the only one?

I would just remove that leaf and bag it or burn it and keep a close eye on the rest of the plants.

[newboy74]

Thank you both - still panic stricken




these are off two othe desiree main crop seed potatoes. I'm tempted to cut everything down including second earlies which have no signs of black spots. If I do will my second earlies keep ok in the soil for a week or two?

[Two_Sheds]

I'd just be taking off the affected leaves for now, and keep a careful eye for more

[newboy74]

oh two sheds, if only I could, I'm going to the mother in laws for four days tomorrow and all I'll be thinking of is getting home to check on my potatoes. I'll have a good look at them before I go i guess. actually - think i'll dig up all the main crops and leave the second earlies alone as they don't seem to be affected thanks

[Two_Sheds]

Well if that's not a good excuse for missing a trip to MiL's I don't know what is

[newboy74]

........... : )

[rustylady]

Have a read of this:

The way to stop blight spreading is to have hot, dry days. Infection is dependent on warm, wet weather, and since the conditions for blight infection are so specific and well understood, periods of high risk can be predicted with some accuracy.

The humidity around plants is increased by watering, and this can accelerate the spread of blight. If watering is necessary it is better to do it from beneath to avoid wetting the leaves.

The conditions under which blight infections can be expected are known as a "Smith Period". This is a 48 hour period in which the minimum temperature is 10°C or more and the relative humidity exceeds 90% for at least 11 hours during the first 24 hours and for at least 11 hours again during the final 24 hours.

Taken from this link Potatoes,DIVERSITY,english,heirloom,varieties,Blight Warnings & Smith Periods

[newboy74]

yes , it shouldn't happen in this weather, I took your earlier advice and held off the watering - mostly. I noticed you said in another post you don't water well established plants at all- sounds sensible in retrospect. Its funny though because I haven't watered the main crop potatoes at all and they are the ones that seem affected. may be its proximity. I'm going to cut them down and leave the second earlies to get on with it. no more watering at all, mind you the midlands seems due for rain next week. Thanks

[rustylady]

Well, it's up to you I suppose.

If you do cut the foliage down be careful to bag it up, not leave it lying around in case it is blight.

[newboy74]

ok, I've cut 70% down now so there is no going back, probably a deadly combination of inexperience, panic, time on my hands and too many early ales on a hot afternoon. its probably just the plant dying back but I have bagged it all up. thanks for all of your advice. hope the badgers don't get the spuds whilst i am away. This growing lark is intense.

[Two_Sheds]

If you do cut the foliage down be careful to bag it up, not leave it lying around in case it is blight.

... but then it can safely go on the compost heap (bury it under other stuff) because [drum roll please] ... blight spores only survive on living tissue, not on dead leaves, so it will die in the compost heap

its probably just the plant dying back

No it's not: die back looks just yellow & pale: no black spots usually

[newboy74]

Thanks Two Sheds, I'm hoping it's this:

"Potato early blight (Target spot) symptoms may be mistaken for late blight. Early blight, Alternaria solani, however generally occurs earlier in the season (July) and spreads under warmer and drier conditions than late blight. The distinctive smaller dark brown spots, somewhat angular with concentric rings, are bounded by the leaf veins. Early blight rarely causes significant loss of yield and no treatment is necessary". (Factsheet about potato blight)

nevertheless, I'm not taking any chances and will treat it like late blight as advised.

[Potstubsdustbins]

Check under the leaves if it is blight they will have a whitish mould fringe around the spot.

Potty