Potato disease/condition? - Ask Extension
Dear Sir!I grow potatoes near Herman, MN, in my family garden. Attached are some photos of Red Pontiac potatoes with holes/pits in them. I'm not c...
Knowledgebase
Potato disease/condition? #167685
Asked February 22, 2014, 12:57 AM EST
Dear Sir!
I grow potatoes near Herman, MN, in my family garden. Attached are some photos of Red Pontiac potatoes with holes/pits in them. I'm not certain I can discern whether this is a chewing bug problem or some disease problem. One interesting thing is that Yukon Gold potatoes that were in adjacent rows (or even occasionally adjacent plants) did not seem to be affected at all.
If this is disease, is it something in the soil, or peculiar to the potato? What are the chances the seed potatoes I purchased were already "carriers" and then it showed up in my crop?
Thanks for your help!!
I grow potatoes near Herman, MN, in my family garden. Attached are some photos of Red Pontiac potatoes with holes/pits in them. I'm not certain I can discern whether this is a chewing bug problem or some disease problem. One interesting thing is that Yukon Gold potatoes that were in adjacent rows (or even occasionally adjacent plants) did not seem to be affected at all.
If this is disease, is it something in the soil, or peculiar to the potato? What are the chances the seed potatoes I purchased were already "carriers" and then it showed up in my crop?
Thanks for your help!!
Grant County Minnesota
Expert Response
Although I am not a plant pathologist, it appears your potatoes have scab. There are two types of scab.
"Common scab" is bacterial. The lesions are corky, and may be raised or pitted. Common scab is prevalent in potatoes, and is often aggravated by dry soil during the 2-week period after tubers begin to develop.
"Powdery scab" is fungal. The lesions are not corky, but often have blotches of dark spores that might require a magnifying glass to be seen. You can google images for each type to compare with your tubers.
No potato variety is immune to scab, but some may be more resistant than others depending on location and other factors. While you had good luck with your Yukon Gold, one Canadian source indicates this variety is actually more susceptible. So I recommend you contact your local extension office to learn which varieties are recommended in your area, and be sure to buy scab-free seed potatoes. See http://www3.extension.umn.edu/county for extension offices.
Here are some preventative steps you can take to avoid scab:
"Common scab" is bacterial. The lesions are corky, and may be raised or pitted. Common scab is prevalent in potatoes, and is often aggravated by dry soil during the 2-week period after tubers begin to develop.
"Powdery scab" is fungal. The lesions are not corky, but often have blotches of dark spores that might require a magnifying glass to be seen. You can google images for each type to compare with your tubers.
No potato variety is immune to scab, but some may be more resistant than others depending on location and other factors. While you had good luck with your Yukon Gold, one Canadian source indicates this variety is actually more susceptible. So I recommend you contact your local extension office to learn which varieties are recommended in your area, and be sure to buy scab-free seed potatoes. See http://www3.extension.umn.edu/county for extension offices.
Here are some preventative steps you can take to avoid scab:
- Plant resistant cultivars and always start with scab-free seed tubers.
- Rotate with non-host crops. A 3-4 year rotation is recommended.
- Maintain adequate soil moisture during and after flowering when the plants are forming tubers.
- Avoid application of soil amendments that increase soil pH. Add peatmoss if the soil tends to be alkaline.
- Avoid application of animal manures from animals fed infected tubers or stems (chickens, cattle, etc.)
