Potato blight?

[Thongmas]

Hi guys I seem to be having no luck at the moment. Could anyone tell me if this is potato blight? These are my main crop spuds which still have a fair way to go, thank you!

[ameno]

No, that's not blight. Or rather, it's not the one you need to worry about.

There are actually two potato diseases called "blight".
Late blight is the one you need to worry about - it causes large, irregular patches of dark grey-brown damage and spreads very quickly, also attacking the stems and the tubers underground.
What you have there looks to be early blight, actually a completely unrelated disease. It causes small circular brown dead patches on leaves, and that's pretty much it. It will not spread to the stems or tubers. In a very bad year it can potentially defoliate a plant and therefore cause a reduction in yield, but that's the worst it ever gets. And early blight thrives more in hot, dry conditions, so it doesn't really take hold that much in this country (unlike late blight, which likes merely warm and damp conditions).

[Thongmas]

Thank you very much. Had me down today thinking everything was going south. Much appreciated for the positive news and help!

[Thongmas]

Bit of an update. It seems some of them are doing quite bad in comparison to almost a couple of weeks back.
Would you guys recommend me do anything with these as they are? Started them outdoors in buckets on the 7th May

[ameno]

Remove any yellow leaves and bin them, but otherwise they seem more or less fine.

Bear in mind that in this hot weather potatoes in pots will need twice daily watering, at least half a gallon each watering.
And don't use a rose, just pour it from the can straight onto the soil. Getting the leaves wet will encourage disease (not to mention it wastes the water, as it's on the leaves and not the soil).

[Thongmas]

I took your advice and I've upped the watering and pouring straight from the can without the rose but unfortunately they seem to have slowed down growth unless I'm imaging it and the blight is only getting worse as shown on the pic.

Would you say only take the yellow leaves off or take any off with the black spots? Thank you

[ameno]

The plants are probably just dying naturally. If they were early potatoes, or even second early, then if you planted them on the 7th of May then they are probably ready now, anyway.
Potatoes don't like excessive heat, anyway, so that may be hastening their demise a little, but I think this was probably around the time they would have started dying back regardless.

I would just leave the leaves on at this point. If you remove all of the infected ones from that plant it won't have any left. That's still only early blight, anyway, so it's not anything to worry too much about (early blight does prefer hot, dry conditions, which is why it has been spreading more quickly just recently).

[Thongmas]

Thanks for the info. These are main crop sarpo mira and it's the first time I've done main crop spuds but I was under the impression these can take around 120 days to mature and they've only been in around 70 or so.

[ameno]

Well, just keep them watered, maybe feed them every couple weeks, and see how they do. Wait until the leaves die back properly before harvesting.

Maincrop aren't really well suited to growing in containers, to be honest. They need more space and more water than they are likely to be able to get in pots.

[Thongmas]

Much appreciated for that.
Would you recommend me taking off the sickly looking yellow leaves and leaving the green leaves with black spots on until they eventually turn yellow also?
I'll definitely put main crop in the ground next time though, cheers.

[ameno]

Leave the leaves until the start fully dying (turning brown all over, more than just the brown spots) before you remove them. Even then, you probably don't really actually need to remove them. You could just leave them, it probably won't make an difference either way.