Reversion Virus is a serious disease that affects blackcurrants.
We are still sourcing a photograph for Reversion Virus. We only use real CC-licensed images, never AI. If you have one to share, we would love to hear from you.
What does it look like?
Leaves on a reverted bush can be narrower than on a healthy one, and vigour and fruit yield fall as the disease progresses. The virus exists in two forms, European and Russian; the Russian form also malforms the flowers. Big buds, the swollen round buds that show the mite is present, are most easily seen in late winter.
What causes it
Big bud mite carries the virus from bush to bush, so controlling the mite is part of controlling the disease. Infected planting material also brings it in, which is why certified stock matters.
Is this disease active now?
Big bud is most easily seen in late winter, and the mites emerge in early summer and crawl over the plant in search of new buds. Malformed flowers in the Russian form show at flowering in spring; the decline in vigour and yield builds over the years rather than on a fixed date.
Controlling the big bud mite is part of managing this disease, since the mite is how the virus moves between bushes. See Big Bud Mite →
Why this matters in Scotland
It is rated higher risk than the mite that spreads it, because the mite can be tolerated, picked off or avoided with a resistant variety, while the advice for an infected bush is removal.
Ben Gairn is a Scottish cultivarA plant variety that arose or was bred under cultivation and is kept true by deliberate propagation, rather than a naturally occurring wild species. Full definition → that resists both the European and Russian forms of the virus, so it addresses the disease itself. Ben Hope resists the mite that carries it, which is a different protection.
Controls: what works
Remove infected bushes: dig up and dispose as soon as diagnosed
Remove a reverted bush promptly once it is diagnosed, because left in place it is a source the mite can carry the virus on from. If it is still carrying a crop, lifting it after the fruit has been picked and replanting in autumn with clean stock is the usual timing.
Certified stock: buy plants certified free of reversion and big bud
Buy plants certified as free of big bud, which have been inspected at the nursery and declared free of the mite, and look for FPCS-certified on the label. Starting clean keeps both the virus and its mite vector off a plot that doesn't have them, which matters because removal is the only answer if it arrives.
Resistant varieties: choose Ben Gairn or another resistant cultivar
Ben Gairn is a Scottish cultivar that resists both the European and Russian forms of the virus; Golubka is another. Resistant cultivars are usually derived from Siberian blackcurrant (Ribes nigrum var. sibiricum) or Ribes dikuscha. Ben Hope resists the mite, not the virus.
Control the vector: manage big bud mite populations
Keeping the mite down is the closest thing to prevention. Pick off the affected buds of lightly infested bushes during the winter, and dispose of heavily affected plants after fruiting.
Myths about reversion virus
“Reversion virus just makes the leaves look different, it doesn't cut the crop”
Reversion debilitates plants and reduces fruit yields, so it is not just a cosmetic change. Leaf changes may be the easiest symptom to spot, which is probably why the myth focuses on them, but the yield decline runs alongside them.
What to do: Treat narrowed or distorted leaves, or malformed flowers, as a sign that cropping is at risk. Get it diagnosed, and remove the bush if it is reverted.
2 sources
- RHS: Blackcurrant big bud miteThe mite can transmit reversion, which debilitates plants, resulting in reduced yields of fruit.
- James Hutton Institute: Blackcurrant reversionDescribes the European and Russian forms, with malformed flowers in the Russian form.
“You can prune out the affected shoots and save a blackcurrant bush with reversion virus”
Neither the RHS nor the James Hutton Institute describes pruning as a control for reversion; the measure given for a diagnosed bush is removal of the whole plant. The bud-picking some gardeners remember from blackcurrant care is a big bud mite control for lightly infested plants, a separate problem, not a treatment for the virus the mite can carry.
Our read The confusion likely comes from big bud mite management including a pick-off-and-dispose step for lightly affected buds. That targets the mite's swollen buds, not reversion symptoms.
What to do: Once a bush shows reversion symptoms, don't rely on pruning. Dig it up and dispose of it, then replant with certified virus-free stock.
2 sources
- RHS: Blackcurrant big bud miteAdvises picking off the affected buds of lightly affected plants in winter and disposing of heavily affected plants after the fruit has been picked, replanting with clean stock.
- James Hutton Institute: Blackcurrant reversionLists removal of reverted bushes from plantations as soon as diagnosed, alongside targeting the mite vector and resistant cultivars.
“Once you've bought certified virus-free blackcurrant stock, that bush is protected from reversion virus for good”
Certified stock is inspected and declared free of both big bud mite and reversion at the point of sale, which is a real and useful guarantee, but it's a guarantee about that moment, not about every year afterward. Big bud mite is the vector that carries reversion, and a mite population can still establish itself in a garden after planting, carrying the virus in from elsewhere. Neither source presents certified stock as removing the need for ongoing mite control.
Our read Certified stock and mite control are listed as separate measures rather than certified stock being treated as sufficient, which suggests a clean start doesn't remove later risk. No source tests this.
What to do: Start with certified stock, but keep checking for big bud mite year to year rather than treating the certification as a one-time fix. If big buds show up nearby, reversion risk returns even on a bush that started clean.
2 sources
- RHS: Blackcurrant big bud miteAdvises buying stock plants certified as free of big bud, inspected on the nursery and declared free of the mite, alongside separate mite-control advice.
- James Hutton Institute: Blackcurrant reversionSays control of reversion is focused on the mite vector.
“Reversion virus can spread to a healthy blackcurrant bush through the soil or touching roots, not just via the mite”
Big bud mite is the vector named for reversion, and neither the RHS nor the James Hutton Institute describes a soil or root-contact route. Nothing found tests soil or roots directly, so this is unproven rather than ruled out. The mite is the thing to watch for.
Our read Absence of a described soil route is not proof that none exists, so the practical advice follows the mite, the only vector named.
What to do: Check healthy bushes for big bud, the sign of the mite, rather than digging them up just because they grow near an infected one.
1 source
- James Hutton Institute: Blackcurrant reversionSays control is focused on the mite vector and describes no soil-borne or contact route.
Frequently asked questions
What should I do first if I find reversion virus in my garden?
The first thing to try: Remove infected bushes. Then: Certified stock.
Is there a spray that works?
No. There are no amateur chemical treatments available for reversion virus. The controls that work are cultural: the measures listed above.
When should I watch for reversion virus?
Big bud is most easily seen in late winter, and the mites emerge in early summer and crawl over the plant in search of new buds. Malformed flowers in the Russian form show at flowering in spring; the decline in vigour and yield builds over the years rather than on a fixed date.
Sources
Show the 3 sources
- RHS1: reversion transmitted by the mite and reducing fruit yields; mites emerging in early summer; certified stock inspected and declared free of the mite; disposing of heavily affected plants after fruiting and replanting in autumn with clean stock; picking off affected buds in winter; big bud most easily seen in late winter; Ben Hope as the mite-resistant cultivar
- James Hutton Institute2: the European and Russian forms and the Russian form's malformed flowers; control aimed at the mite vector; removal of reverted bushes as soon as diagnosed; sulphur sprays aimed at the mite; Ben Gairn and Golubka resistant to both forms, resistant cultivars usually derived from Ribes nigrum var. sibiricum or Ribes dikuscha, from the Hutton blackcurrant breeding work
- RHS1: buying plants certified virus-free and looking for FPCS-certified on the label