Blackcurrant big bud mites are microscopic, much less than 1mm in length. They live inside dormant buds and suck sap from the embryonic leaves. Affected buds become abnormally swollen and rounded. The mite can also spread reversion disease.

• Symptoms of the mites are most easily seen in late winter, when affected buds become abnormally swollen and rounded
• Healthy buds are pointed and longer than broad
• Affected buds often dry up, producing no leaves in spring, or stunted foliage and few or no flowers

Non-pesticide control

• Affected plants can continue to crop well for several years and so some presence of the mite can be tolerated
• Dispose of heavily affected plants after the fruit has been picked and replant in autumn with clean new stock
• Purchase stock plants certified as free of big bud and reversion, these will have been inspected on the nursery and declared free of the mite
• One mite-resistant cultivar, ‘Ben Hope’, is available
• The affected buds of lightly infested plants can be picked off during the winter and disposed of away from blackcurrant plants

Pesticide control

No pesticides are available to home gardeners for the control of blackcurrant big bud mite.

• A blackcurrant bud can host hundreds of mites, which feed by sucking sap from the embryonic leaves
• The mites emerge in early summer and crawl over the plant in search of new buds
• They can be blown by the wind onto other blackcurrant plants
• The mite can also transmit a virus-like mycoplasma disease known as reversion. This debilitates plants, resulting in reduced yields of fruit