Sorry! Lets try this again with the correct flair…
It’s a balmy -22c (-8F) today in Alberta and I was staring at my raised beds in their sad frozen state. So of course this is the perfect time to start thinking about spring time & my garden to mentally get through the next few months.
Onto the Questions! I have a 10 foot x 4 foot raised bed that I threw some potato’s in last year. I love growin the spuds! I just find them so satisfying…as the picture shows they ended up with Scabs (oh well) harvest was still good! I had both Yukon Golds & a Red type. Neither were super high quality seed potato’s. So I am pretty sure these were the culprits. I purchased my house in Feb 2025 and the raised beds were from the prior owner & they had only grown flowers in it the year prior. Not sure about years prior…
Now after some reading im wondering if I’ve doomed myself for future potato crops by potentially infecting the soil with the sub-par seed potato’s.
Does anyone have tried and true methods for preventing scabs the next year? Testing PH..? I read something about molasses being mixed with water..? New soil..? Is it even possible!
I know scabs aren’t the end of the world but just one of those things i’d like to amend.
by shytatie
12 Comments
From my understanding it’s a viral disease that is not easily if at all possible to get rid of. Make sure not to use the same seed source next year and plant in another area next season.
I have used powdered sulfur in the past and it does limit the amount of scab but isn’t a silver bullet.
Scabby potatoes look a bit gnarly, but they’re perfectly fine to eat and usually store just fine as well. Just FYI! Scab is a much bigger problem for commercial growers who need pretty crops for sale than for home gardeners who are feeding themselves.
If you want to work on the problem, then mildly-acidic soil is the best short-term option to reduce the extent of scab that you’re seeing. Sulfur is generally good for this purpose and is also an excellent amendment for potato plant health, but do a soil test before you dose anything. You can also lean into thicker-skinned potatoes for a season or two, like Russets, that tend to take less scab damage.
(Molasses sometimes gets brought up in these conversations about potatoes and scab because it sometimes contains minimal amounts of sulfur, but you can just dose sulfur directly for a better effect.)
We got some scabs but we attributed it to that week where we cut off the brown dead tops getting ready to harvest, some things happened and it rained on our grow bags, then when we finally did get around to harvesting them they had scabs. Did your potatoes have very moist soil at the time of harvesting? Maybe you could cover the bed at the end of their life to keep the soil dry? I’m very new to gardening myself.
acidify the soil below 5.2 use seed potatoes that are scab resistant.
Potatoes with scab are edible, just peel off the scabs. Potato scab is caused by a bacterium (you can look up a more detailed description online.) There are several ways to help decrease the likelihood of potato scab. First, rotate your crops if possible. Don’t grow potatoes in the same soil every year. Don’t use fresh manure before planting your sets, the bacteria can be harbored in fresh manure. Keep your soil evenly watered, potato scab likes dry soil. And finally, potato scab likes alkaline soil, so you need to raise the acidity level. Sulfur is one way. Some potatoes are more susceptible, some more resistant. Do some research for your area. In our experience, russets are generally more tolerant, Yukon gold are not. Happy Gardening!
I’ve heard lowering PH, raising moisture levels during tuber formation and rotating crops with things like barley/clover are your best bets.
There are some articles about fighting it on various university ag sites but I think there are several types of scab and your specific soil/climate may factor in.
Your soil needs to have a lower ph. And if you’ve used animal manure compost you will have scab. Try growing in a different area of your garden and have the soil pH checked. Sulphur will help lower ph. Potatoes like ph below 5.5.
Nowt wrong with those potatoes. Good growing!
Potato common scab is a casual fungus which can be soil or seed borne.
Suggest following
A. Rotate your land to grow potatoes 1 year in 5 years on same land
B. Check ph and amend to 5.5 to 6.5 . Sulphur soil treatment
C. Grow preferentially scab resistant varieties
D. Use certified seed .
E. If variety is susceptible to scab, irrigate from tuber initiation to flowering stage, then reduce frequency.
F. Only use well rotted manure in seed bed.
But always keep a strict fungicide spray programme to control late potato blight.
Apparently a crop rotation with
Medicago Sativa or Secale Cereale gets antagonistic Bacteria into the ground who counteract the causing bacteria, whilst having carrots before potatoes is aking it worse…
Edit:
the first plant has the benefit of also having nitrogen accumulating bacteria, thus acting as a renutrification agent if choped and worked into the soil after growing…
What ive done is taken a bag and mixed my seed potatoes with sulfur at planting.
When planted its basically dusted in sulfur.
Ive never had a scab problem doing this.
Don’t amend the soil with manure and use sulfur. When I make a furrow for the seed pieces, I sprinkle sulfur in the furrow between the seed pieces.