Potato Disease Diagnosis Help Needed

molloyv · Rank attained: Hazel Tree Joined: 28 Jun 2009 Posts: 7

My earlies (Home Guard) have some sort of disease - see pictures below. When the plants originally came up, two of them went bad (I thought blackleg, so dug them out).

Two other plants have poor growth, yellow leaves and spots. They've been like this for a while but I was reluctant to pull out (as half my earlies would be gone !!!).

I know the earlies are due to be dug up soon anyway but the yellowing and spots have started to spread to my previously healthy early plants. I have maincrop (Sarpo Mira) in the same bed and dont want it to spread to these.

Any advice appreciated.

michael brenock · Posted: Sun Jun 28, 2009 9:01 pm Post subject:

if you pull up the stalk and if it comes up easily and is soft and rotten at the base then you have a bacterial disease called black leg. it spreads earlier in the year but only manifests itself when the plant cannot get water up the stems, it will not spread from one stalk to the next. Mostly spread by seed. The other symptoms the yellowing and black spots are secondary.
michael brenock horticultural advisor (retired)

molloyv · Rank attained: Hazel Tree Joined: 28 Jun 2009 Posts: 7

Thanks Michael. Do you reckon the seed potatoes I used were infected to begin with? And is there anything I can treat with ?

michael brenock · Posted: Mon Jun 29, 2009 12:44 pm Post subject:

either the seed potatoes were infected or the infection came from a previous crop of potatoes in the ground. there is no practical treatment except hygiene and rotation. it does not spread from stalk to stalk during the growing season.
michael brenock horticultural advisor (retired)

molloyv · Rank attained: Hazel Tree Joined: 28 Jun 2009 Posts: 7

Thanks again Michael. First time growing anything in the garden. This time last year it was all grass - so must be the seed potatoes.

Liparis · Posted: Mon Jun 29, 2009 2:19 pm Post subject:

Make sure you lift every tiny spud and dispose of the foliage on a bonfire, just to be safe for next year.
Bill.

molloyv · Rank attained: Hazel Tree Joined: 28 Jun 2009 Posts: 7

Thanks Liparis. I'll be sure to get them all out.

I couldnt wait any longer so this evening I pulled up the spuds from one of the healthy plants. You can see them washed and weighed - approx 840 grams. I had them for dinner and they were without doubt the nicest potatoes I've ever eaten! The vegetable garden is here to stay.

Just curious as regards the yield. There were quite a few small tubers so I presume if I left them a bit longer, I could have easily got a yield of over 1Kg. I know I'll find this out for myself in the next couple of weeks but I wonder do any of you have any opinion on whether taking them out early and small gives a tastier spud or does it make any difference?

As regards the ailing plants, I dug out one tuber and it was a decent size and looked perfectly fine. So fingers crossed.

michael brenock · Posted: Mon Jun 29, 2009 9:34 pm Post subject:

the potatoes look wonderful. The flavour will improve as the potatoes mature.
michael brenock horticultural advisor (retired)

Liparis · Posted: Tue Jun 30, 2009 9:46 am Post subject:

molloyv · Rank attained: Hazel Tree Joined: 28 Jun 2009 Posts: 7

Thanks Michael and Liparis. I'm already looking forward to digging up the next lot Very Happy

. Will take out one of the ailing plants first as suggested.

Organicgrowingpains · Posted: Tue Jun 30, 2009 7:05 pm Post subject:

Another ailing spud story! I dug the first lot of Orla yesterday , not a great yield some were much bigger than others.i used the smaller ones for salad. I would have to say they have a better taste than the Colleens. A lot of them had worm? holes.Are these our earth worms chomping on good pops instead of waste or something else?
I also came across a yellowed tuber in the Kerr's pinks which I pulled out ,that query may have been answered by the above.I did not dig around for any spuds underneath just pulled up the stalks which came out freely.

michael brenock · Posted: Tue Jun 30, 2009 7:54 pm Post subject:

That damage looks very like slug damage to me but it is very severe. There must have been a small black slug within the tuber when you cut it. You may not have planted the seed potatoes deep enough because this looks like damage near soil level.
michael brenock horticultural advisor (retired)

Organicgrowingpains · Posted: Tue Jun 30, 2009 9:08 pm Post subject:

Hi Micheal, thanks for that. The seeds were planted quite deeply, in fact I thought they would never come up! They are next to the grass path and in an area which has not been cultivated for years and had been wild.This was our no dig area which was covered with kitchen waste, manure, cardboard and black plastic. There are only 2 drills of them so hopefully they will not go any further.

Liparis · Posted: Tue Jun 30, 2009 10:56 pm Post subject:

Slug damage it most certainly is, unfortunately you have keeled slugs a very devastating potato pest. Very rarely seen above ground they live and feed in down in the soil. Usually by the time your lifting the spuds the slugs have done the damage and moved on through the soil.
Sign of damage is usualy a round hole in the side of the tuber and when you cut it open you find more extensive damage inside as you have done.
Nematodes would be the answer for these species (Milax genera), perhaps one of our more experienced googlers can help?
Bill.

Organicgrowingpains · Posted: Wed Jul 01, 2009 8:50 am Post subject:

Hi Liparis, I am going to lift some of the other pops this morning to see how they are.I am devasted! Blight last year and keeled slugs this year.I am putting up a photo of where they are planted,taken some weeks ago. From the top, 2 drills of Orla,4Colleen,2Charlotte,1 Home gaurd seed and nearest 1 drill of volunteers.I started digging the Colleens first and they were OK but if these slugs can move fast all of this area of earlies could be destroyed!