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All problems at once on blackcurrants? #870436

Asked May 28, 2024, 1:52 PM EDT

Hi! I am living in Stockholm, Sweden but I used to be a Maryland residents for couple of years until 2023 so I can’t think of a better place to ask. My blackcurrants (cultivars are Risarp and Öjebyn, planted in containers and successfully overwintered in a shelter) seem to have all problems at the same time and I have no idea why. I am in USDA zone 7a equivalent. I see different kinds of pathological morphologies appear on the same plant, same stem, while the new leaves keep sprouting and seem fine. For one day, it looks like reversion disease. For another day, it looks like fungi… It is at the same time that these pathology occurred that some of my other plants on the balcony, that were just budding fine, started to mysteriously die. A P. nipponica that was about to bloom suddenly stopped growing and died, together with a ginkgo stem. I thought of a generalist pathogen, but that has to be such a wild generalist… meanwhile my American blueberries, a p.serrulata, and a S. vulgaris, all in the vicinities, are perfectly fine. I am so incredibly confused. I’d greatly appreciate some pointers!

Howard County Maryland

Expert Response

Thank you for the compliment, but we are not familiar with currant ailments outside of the Maryland region, much less in Sweden. Container-grown plants tend to be more stressed than those in the ground (we realize you may not have the option to grow in the ground), and that can be an underlying factor for a variety of opportunistic pests or pathogens. The yellowing leaf pictured looks like normal senescence of older growth (especially if the plant is running low on nitrogen, which easily leaches out of containers due to the more frequent watering), though we don't know what caused the slight amount of puckering on other leaves. (A late spring cold snap as foliage or buds were still expanding weeks ago might be responsible.) Sap-feeding insects like aphids (even if gone now) or leafhoppers can also distort foliage.

You are correct that it's unlikely a single pathogen is responsible for symptoms across multiple unrelated species. Those pathogens that do have wide host ranges tend to target plants already under stress (even if they are not yet manifesting obvious symptoms of stress), such as from under-watering, over-watering, or injury from temperature fluctuations (frosts or high heat).

We do not know if Sweden has the equivalent of an Extension service to ask, but any resource to help home gardeners would be where we suggest going for more information. Perhaps a local University has a plant pathology or horticulture department that takes questions from residents.

Miri

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