Northwest berry Foundation

Management Detail

Redberry Mite

in Blackberries

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Latin name: Acalitus essigi


Reason for Concern:
1) A perennial pest of cultivated and wild blackberries.
2) Impacts Evergreen and Chester blackberries heavily, but other caneberries are susceptible.
3) Fruit/drupelets do not ripen. Isolated infestations can spread to sizable planting portions the following season.
4) Most damaging to late-maturing blackberry cultivars.
5) Prevents proper drupelet maturation as mites inject a toxin while feeding.

Microscopic, 1/50” long with 2 pairs of legs. Adult is wormlike and translucent white. Irregular ripening. Drupelets remain green or bright red on black and fully ripe fruit.

Life Cycle:
Redberry mites feed at drupelet bases, cores and stems, and overwinter in bud scales or deep in buds.

Commercial blackberry growers estimate that redberry mite can cause 10-50% loss in total yields. In a few instances, blackberry growers claim that redberry mite caused up to 100% loss on other late maturing varieties. Since economic damage almost always occurs in the late ripening cultivars Evergreen blackberry and Chester, it is generally not economic to apply preventative sulfur applications on other cultivars.



  • As fruit develops, Examine field for irregular ripening fruit that has brick red drupelets (either several on a fruit, or an entire fruit), that do not fully ripen.
  • Examine suspected fruit under a high powered microscope (greater than 15x magnification) at the base of the drupelets. Adult mites are 1/50” long, with white, wormlike bodies and 2 pairs of legs.
  • If mites are identified as a problem, it is only possible to begin a treatment program for the following year as there is no effective inoculation after symptoms have appeared.

Cultural Controls:

None listed at present.


For information about chemical controls, check with our Pesticide Guide.


photo from University of California

Damage from redberry mite - photographer unknown

photo by T. Peerbolt

photo by T. Peerbolt


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