Dormant buds of black currants are swollen into big round balls

Black Currant Gall Mite

Left branch of this photograph has dormant bud infested with black currant gall mites. The right branch is un-infested and is leafing out normally. Photo courtesy of Rex Brennan, Scottish Crop Research Institute.

Infested black currant bud that has been cut in half. The black currant gall mites are the small white worm-like creatures between the bud tissues. Photo courtesy of Rex Brennan, Scottish Crop Research Institute.

Close-up view of an infested black currant bud taken with a scanning electron microscope. The round objects are mite eggs. The worm-like creatures with legs near their head end are the mites. Photo courtesy of Rex Brennan, Scottish Crop Research Institute.

• Causal organism: Cecidophyopsis ribis Westwood, Europe and New Zealand
  NOT FOUND IN NORTH AMERICA
• Crops affected: Black currants.

This mite causes dormant black currant buds to grow into big round balls. An infested dormant bud cut in half will reveal many, many tiny white worm-like creatures (mites) inside of the bud tissue. These mites do not occur in North America. Currant plants from other countries must first go through quarantine inspection and testing to prevent these mites, and the disease that they carry, from entering this country.

These mites can carry a virus called black currant reversion virus. The mites and the virus are deadly to commercial production of black currants in Europe and New Zealand. Both the mites and the disease should be kept out of North America.