Big bud mite (Cecidophyopsis ribis)
Also known as Gall mite, this microscopic (1/4 mm long) white mite lays its eggs in buds from June until spring. Many thousands of mites can infest each bud. As they suck sap from the developing leaves, they cause the bud to change shape and swell, sometimes forming galls. By the spring, the buds may be dry and leaves fail to emerge.
From April until July, the mites emerge from infected buds and then spread to surrounding buds and plants, often transported by passing insects, by wind or even rainsplash. The blackcurrant's relatives, gooseberries and redcurrants are also affected but without the chatacteistic big buds.
Yields may be reduced but far more important than it's direct effects is the fact that the mite transmits reversion virus.
- Enlarged buds from late summer:
- spherical appearance unlike the normal pointed appearance of buds
- up to twice the size of normal buds by autumn
- most visible when leaves have fallen in the autumn
- Buds may turn into galls
- In spring buds fail to open or leaves are stunted
Prevention & control
- Buy certified diseas-free plants
- Grow resistant varieties e.g. 'Ben Hope'
- Remove and burn enlarged buds in winter/early spring before mites emerge to spread
- Cut out and burn severly infested stems, removing badly affected plants completely