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.
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