Redberry mite

The Redberry mite is only 0.18 mm in size, translucent white and cannot be seen without a magnifying glass.

Also known as:
Blackberry Mite

Door de bramengalmijt aangetaste bramen, foto: CC0 Public Domain

Redberry mite (Acalitus essigi) is only 0.18 mm in size, translucent white and cannot be seen without a magnifying glass. This mite lays eggs in the flowers of the blackberry. The resulting blackberries remain red or green and hard. These blackberries no longer ripen and often overwinter on the branch.
The females of the Redberry mite overwinter hidden in the buds; in March the mites become active and lay eggs in the flowers.
All blackberries can be affected by Redberry mite; however, gall mites prefer late blackberries (Thornless Evergreen, Reuben, Chester Thornless).

Where to find

Control

Remove affected fruit and branches.

Prevention

Cut back fruit-bearing branches early in the fall, especially those that have immature red or green remaining blackberries on them.
This prevents the female bramble mite from overwintering in those branches. This prevents any population from spreading further.