Pest
Big bud mite
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Watch for | Watch for in January | Watch for in February | Watch for in March | Watch for in April | Watch for in May | Watch for in November | Watch for in December |
What it is
Big bud mite is an eriophyid mite far too small to see without a lens. Thousands live inside a single blackcurrant bud. The direct damage is lost buds and weaker crops, but the more serious problem is that the mite carries blackcurrant reversion virus, which slowly ruins a bush.
Symptoms
After leaf fall, infested buds stand out as swollen, rounded and pale, like tiny cabbages or peas, while healthy buds are narrow and pointed. In spring these buds dry up instead of opening, so shoots have bare gaps. Bushes infected with reversion have leaves with fewer lobes and fewer main veins, flowers that look brighter and more hairless, and cropping that declines year on year.
Cause
Mites breed inside the buds through autumn and winter. In spring, around flowering time, they leave the dying buds and crawl or are carried by wind, insects and birds to new buds, often on neighbouring bushes. Each mite moving between plants can spread reversion if it has fed on an infected bush.
Control
Check bushes between November and February and pick off every swollen bud, putting them in the bin rather than the compost. On a lightly affected bush this can keep numbers down. If most buds are swollen, or the leaves show signs of reversion, dig the bush up and dispose of it; there is no cure for the virus. Chemical control is not available to home gardeners in a useful form.
Prevention
Buy certified, virus-free bushes from a reputable nursery and plant them away from old or neglected currants. 'Ben Hope' was bred with resistance to the mite and is worth choosing where the pest is common. Avoid taking cuttings from bushes with any swollen buds. Replace ageing bushes every ten to fifteen years.
Plants often affected
Could it be something else?
These problems share some of the same symptoms. Compare them, or run the symptom checker with these signs ticked.
Months to keep an eye out: January, February, March, April, May, November and December.
Sources
Identification and life-cycle details were checked against the references below. Text and advice are our own. See our editorial policy.