A trial participant from southern Vancouver Island contacted us about yellowing on the leaves of her potatoes:
“Some of my plants are not looking so good. I wonder if you can tell by looking at the photos what the problem might be. I wonder if I have not been watering them deeply enough and therefore there is a drought problem around the roots.”
Russet potato showing yellowing on leaves
There is not much unusual about your potatoes.
Yellowing is widespread in mine I think because of early drought and potatoes basically moving in to the late maturity stage because of some warm temperatures a few weeks ago.
Cariboo potato showing yellowing on leaves.
I think I see some flea beetle damage (little shot holes in the leaves). Also very typical and much to be done, I think they do not have a huge impact on yield.
The touch of brown on the leaf spots may indicate blight, not surprising because it has been so wet lately. I have some German yellow potatoes that show this much more severely. You can cut off the blight bits, but avoid having leaves wet (hard to do with this rain). I think I will harvest my German Yellows to avoid having the blight spread. You can probably still give deep watering and bulk up the tubers, However water below the leaf crown.
Information on Leaf Yellowing in Potatoes
Yellowing of the leaves in potato plants is a natural indication that the plants are reaching maturity. By this stage, the tubers are close to their full size, but will continue to add density and cure as the leaves die back.
If they occur early in the season, yellow leaves may be telling a different story.
A lack of nitrogen
may cause the leaf to become pale – rather anemic looking. Amending the soil by adding some nitrogen may allow the potatoes to recover.
Fusarium wilt and verticillium wilt
can also cause leaf yellowing, starting with older, lower leaves. Both are made worse by stress from too much or too little rainfall. Both diseases are mainly soil-borne, and may be moved to new areas from infected seed potatoes or from soil. Strict crop rotation is important to prevent build-up of pathogens in the soil. If you suspect these and other diseases, don’t save seed potatoes from this crop.
Early and late blight
diseases cause dark spots on leaves which may be surrounded by yellow ‘haloes’.