Reversion Virus is a serious disease that affects blackcurrants in Scotland. Here is what it looks like, the conditions it needs, and the controls that actually work.
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What does it look like?
Leaves become narrower and distorted compared with a healthy bush, growth increasingly looking like a wild blackcurrant rather than the cultivated variety it should be, which is where the disease gets its name. Vigour and fruit yield decline as it progresses, and with the Russian strain specifically, flowers become visibly malformed.
What causes it
This virus doesn't spread on its own: it needs big bud mite to carry it from an infected plant to a healthy one, with no other transmission route known. A garden already dealing with a big bud mite population has an active transmission risk running; a garden without the mite has essentially none.
Is this disease active now?
Flowering time in spring is when the clearest sign of Russian-strain infections, malformed flowers, is visible. The general decline in vigour and yield both strains cause builds through the whole growing season rather than showing on a fixed date.
Everything on that page about controlling the mite is worth reading as part of managing this disease too, since it's the only route the virus has to move between bushes. See Big Bud Mite →
Why this matters in Scotland
This is rated higher risk than the mite that spreads it, because a mite population responds to predictable methods, hand-removal, hygiene, resistant varieties, while an infected bush has no method that reverses it once the virus is there.
Ben Gairn is the Scottish-bred answer to that gap: a blackcurrant variety with real Scottish breeding provenance, resistant to reversion itself rather than just to the mite. Big bud mite, the only known vector, already has its own resistant variety on this site in Ben Hope; choosing a variety resistant to both covers the whole problem at planting time rather than half of it.
Controls: what actually works
All the methods below are backed by real evidence, not just repeated folklore.
Remove infected bushes: dig up and dispose as soon as diagnosed
A diagnosed bush won't recover, and left in place it keeps acting as a source the mite can carry the virus on from. Removing it promptly limits how far an existing infection can spread rather than leaving it to decline where it stands.
Certified stock: buy plants certified free of reversion and big bud
Starting clean avoids bringing either the virus or its mite vector onto a plot that doesn't have them yet, which matters more here than with most diseases since there's genuinely no cure to fall back on if it arrives.
Resistant varieties: choose Ben Gairn or another resistant 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 →
Ben Gairn's resistance is bred from wild relatives in Ribes, the currant and gooseberry genus, and covers both known strains of the virus, European and Russian, rather than just one.
Control the vector: manage big bud mite populations
The winter hand-removal, certified stock and resistant-variety controls covered on this site's Big Bud Mite page are just as much a part of managing this disease as anything listed here, since cutting off the mite population is the closest thing to a preventive measure this disease has.
Myths about reversion virus
4 common claims about reversion virus, checked: 3 busted1 disputed0 untested0 hold up
“You can prune out the affected shoots and save a blackcurrant bush with reversion virus”
Reversion virus is systemic in the bush, not confined to the shoots showing narrowed leaves, so cutting those stems out doesn't remove the infection. Neither institutional source describes pruning as a control for reversion once it's diagnosed; both point to removing the whole plant instead. 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 also carry.
Our read The confusion likely comes from big bud mite management genuinely including a pick-off-and-dispose step for lightly affected buds. That's real, but it targets the mite's galls, not reversion symptoms, and RHS keeps the two responses distinct: bud-picking for light mite infestation, whole-plant disposal for reversion.
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 miteRecommends disposing of heavily affected plants entirely and replanting with clean stock, while bud-picking is offered only as a mite control for lightly affected plants, not as a treatment for reversion.
- James Hutton Institute: Blackcurrant reversionLists removal of reverted bushes from the plantation as soon as diagnosed as the control measure, with no mention of pruning out affected growth as an alternative.
“Reversion virus just makes the leaves look different, it doesn't actually cut the crop”
Both sources tie reversion directly to reduced fruit yield, not just a cosmetic leaf change. The narrowed, distorted leaves are the easiest symptom to spot and give the disease its name, which is probably why the myth focuses on them, but the yield decline runs alongside that, not instead of it.
What to do: Treat visible leaf distortion as a sign the bush's cropping is already declining, not a purely cosmetic issue to tolerate. Diagnose and remove the bush rather than waiting to see if fruiting holds up.
2 sources
- RHS: Blackcurrant big bud miteStates that reversion debilitates plants, resulting in reduced yields of fruit.
- James Hutton Institute: Blackcurrant reversionDescribes reversion through its effect on buds and flower malformation as part of a disease that reduces plant vigour, alongside the leaf symptoms.
“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 means of transmission from an infected plant to a healthy one, with no other route documented. That matters practically: a healthy bush planted near an infected one isn't automatically at risk through the soil, root contact, or pruning tools the way some virus diseases spread. The mite is the thing to watch for, not general proximity.
What to do: Don't dig up or isolate healthy bushes just because they're growing near an infected one. Focus on checking for big bud mite galls instead, since that's the actual transmission risk.
1 source
- James Hutton Institute: Blackcurrant reversionStates big bud mite as the vector transmitting the virus between plants, without describing any soil-borne or contact route.
“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. Reversion has no known transmission route except big bud mite, and a mite population can still establish itself in a garden after planting, carrying the virus in from elsewhere. Neither source frames certified stock as removing the need for ongoing vector control.
Our read Both sources list certified stock and vector control as separate, ongoing measures rather than certified stock alone being treated as sufficient, which reads as an implicit acknowledgment that a clean start doesn't remove later risk.
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 mite galls show up nearby, that's when reversion risk returns even on a bush that started clean.
2 sources
- RHS: Blackcurrant big bud miteRecommends buying stock plants certified free of big bud and reversion, inspected and declared free of the mite at the nursery, alongside separate ongoing mite-control advice.
- James Hutton Institute: Blackcurrant reversionIdentifies big bud mite as the means by which reversion spreads from an infected plant to a healthy one, with no other transmission route described.
Frequently asked questions
What should I do first if I find reversion virus in my garden?
Start with remove infected bushes. After that, certified stock. Work through the rest in order of how well-evidenced they are if the first two aren’t enough on their own.
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 are reversion virus most active in Scotland?
Check the seasonal activity section above. Scottish timings can run a few weeks behind the UK-generic figures.
Sources
3 sources, recorded with what each was used for
- RHS1: the debilitating effect and yield reduction caused by reversion, certified stock free of big bud and reversion
- James Hutton Institute2: the two virus strains and the Russian strain's flower malformation, transmission by big bud mite, removing infected bushes, Ben Gairn's resistance to both strains bred from wild Ribes relatives
- RHS1: FPCS certification as the named scheme for virus-free blackcurrant stock