8

We have a row of 3 different heirloom potato varieties, 50 originally, of which we've lost about 15 to a problem we'd like to identify.

The following photos show the start of the issue, through to a completely wilted and near dead plant over the course of about 3 to 7 days.

1 2 3

Neighbouring healthy plants don't appear to have the issue, which seems randomly placed along the row...

Some more info, hopefully helpful:

  • Our region, north of the North Island of New Zealand, is currently experiencing very dry conditions. We've kept the plants well hydrated around every 3rd day, and while we have lost a couple to lack of water the result of that is more obvious (they dry up and die much faster and as a complete plant and the issue above often appears to affect half of the plant initially).
  • The potatoes were planted later in the season than normally. The same varieties at another location nearby, but planted earlier, are thriving.
  • No obvious caterpillars or insects on the plant or damage to the base.
  • They've been fed liquid seaweed twice (as per recommended concentrations and duration between feeds).
  • We've mounded once so far.
  • We garden organically.

Any identification of the cause, tips for next year and/or remedy for this year greatly appreciated.

EDIT: We dug up some of the plants yesterday, the badly affected ones had slimey sacks left of their tubers, and interestingly none presented with a black insides. We also pulled out some that were only just on the turn, but their tubers appeared quite fine.

Graham Chiu
  • 23,044
  • 5
  • 36
  • 92
Lamar Latrell
  • 243
  • 3
  • 7
  • what do the roots of the dead plants look like? – Graham Chiu Jan 03 '18 at 23:27
  • Blackleg looks to be a possibility, judging by the colour of the stems,which get darker towards the base. Dig a plant up and check the tubers - if they're soft and rotting, its probably black leg. – Bamboo Jan 04 '18 at 00:21
  • @GrahamChiu, haven't looked yet, but will do next time we're up at the farm. – Lamar Latrell Jan 04 '18 at 00:46
  • @Bamboo, Ok, thanks for that, I just looked at blackleg online and it does look very familiar! Will be interesting to see the state of the tubers next time we're up there. Some of the seed potatoes did look a little worse for wear... – Lamar Latrell Jan 04 '18 at 00:48
  • 3
    If its blackleg,you need to get those plants out and burn or dispose of them asap - and rotate other crops in the area where its been this year, don't grow potatoes there again next year – Bamboo Jan 04 '18 at 00:57
  • Bamboo...don't plant any of the solanacaea family in or near that soil, right? I've been hearing rotation is across the board two year no plant. I love pots. They really help enlarge the garden. Is Black Leg a blight? Never heard of Black Leg. What about removing the plants, roots as much surrounding soil as possible then using a propane torch, to fry the soil? I am reaching a bit too far...grins! I'll just quietly slip away to go look this stuff up.... – stormy Jan 04 '18 at 09:02
  • @Lamar Latrelle Were your seed potatoes certified? First season? I would contact your supplier or nursery. The company would love to know and would give you new seed potatoes to boot! I would plant potatoes in potting soil and 10 gallon pots with a vertical cage and do the straw thing. Keep garden soil out of your pots, keep your pots away from the area of these with disease. Pots help make this rotation thing with Solanaceae, the Brassica family easier actually extending the size of your garden. Rotation is very very important. – stormy Jan 04 '18 at 09:14
  • @stormy Nope - blackleg (if caused by Pectobacterium) is specific to potatoes and sometimes kale type crops, not other solanums – Bamboo Jan 04 '18 at 15:52
  • So this crosses over solanaceae with brassicas? Always use certified seed potatoes...I've got to go spend some time looking up BlackLeg to see if it is something I might even know. Grins. Thanks, Bamboo. Bacteria versus fungal...hummm. – stormy Jan 06 '18 at 02:02
  • @LamarLatrell Please more information; were these certified seed potatoes? What was planted in that soil last year? What does Organic Gardening mean to you? This definition is messing up an awful lot of gardeners. Remember, any thing we humans do with the out of doors world is artificial. Period. We humans are responsible for the health of the plants most certainly our edibles and that takes basic botany. Organic is a humongous word. Natural and Organic are two words that are over used and misunderstood. Not your fault. Calling fertilizer plant food is wrong. – stormy Jan 06 '18 at 02:11
  • We dug up some of the plants yesterday, the badly affected ones had slimey sacks left of their tubers, and interestingly none presented with a black insides. We also pulled out some that were only just on the turn, but their tubers appeared quite fine... – Lamar Latrell Jan 06 '18 at 05:26

1 Answers1

1

caliche clay raised beds first season

pumice soil after 2 seasons new greenhouse built over

Raised beds. No matter the soil. Forget about sides. This is all done at the beginning with a simple shovel. Piles of decomposed organic matter nearby to throw into the bed you are double digging. Clay, loam, sand or pumice...this is the only way to go. See the trenches? That really improves drainage and control of where you want extra water to go. Cleaning the trenches out twice a year throws more soil on your bed that is also twice per year covered with 2" of decomposed organic matter. The causes a live soil continually being mixed, aerated and fed with decomposed organic matter.

I always add fertilizer. Each bed of plants, each type of plant needs very specific additions of fertilizer. Minuscule additions but critical. I also know the pH of the soil; the garden beds and pot soils. Potatoes love very acidic soil. Those are potatoes in the second picture. Tomatoes are in pots. There will be no tomatoes, potatoes or peppers or egg plant planted in those beds for two years. Pots really enlarge your garden. The control over soil in pots sure make this rotation stuff easier. If you want a great potato harvest you will need to check the pH and make sure your soil has 'tilth', friablity, fluffed...or your tubers won't be happy and well formed. I never dig my raised beds after the first time. Just cleaning the trenches out helps to recycle the soil, feed the soil (lots of decomposed matter washes off the top where decomposed organic matter should be applied AFTER the plants are up from seed or starts), should never grow in decomposed organic matter alone. Soil has to be incorporated.

Black Leg disease

This is as bad as diseases get and are quite normal when gardeners try using non certified seed potatoes. Frustrating for sure. Without hands on examination with my little microscope it would be safe to assume you've got bad bacteria or bad fungus in that soil. I would not even try to plant potatoes or tomatoes or peppers or kale or broccoli or cauliflower...in that soil for at least 2 years.

Hope this helps. These raised beds make a world of difference with success growing any plants. Healthy plants are able to resist disease and insect problems. I think this would help you out an awful lot...done just once. It just takes one bad bacteria or one bad fungal spore to undo all of your work. We all have to learn this lesson for ourselves. I've h.r of mistakes to learn this stuff.

One other thing you must do is remove all the plant material and tubers! Whether they are rotting or not they will be harboring this bacteria. Or fungus. Do not leave a single potato tuber if you can possibly manage. Easiest to start double digging, pull out tubers and make some good plant beds for next year. You do not want to use a rototiller for your clay soil. Just the shovel, turn over each shovel full, chop chop a bit, pile up as you dig down at least a foot if not 18 inches. Depends on your soil, environment and your plant association...

stormy
  • 40,098
  • 3
  • 31
  • 75