Advice

Raspberry leaf and bud mite (Phyllocoptes gracilis)

Plants affected

Raspberry

Symptoms

Pale yellow rounded blotches develop on the upper leaf surface from late May onwards. The undersides of these discoloured areas are slightly darker green than the rest of the leaf. By mid-summer the foliage may be extensively blotched and leaves at the shoot tips become misshapen.

No significant reduction in cane height or fruiting occurs, unlike virus infections with which the mite damage can be confused. Yellow blotches caused by viruses are more angular and associated with the leaf veins.

Biology

The microscopic mites overwinter beneath the bud scales and move onto the undersides of the leaves in late spring. They feed by sucking sap and cause the yellow blotching. Heavy infestations may cause some malformation and uneven ripening of fruits; otherwise this pest is not as damaging as the leaf symptoms might suggest.

Control

No pesticides are available to gardeners against this mite, so infestations have to be tolerated.

Some raspberries are more susceptible than others. 'Glen Ample', 'Glen Shee', 'Malling Jewel' and 'Malling Enterprise' are highly susceptible; cultivars little affected by the mite are 'Glen Lyon', 'Glen Rosa', 'Glen Prosen', 'Glen Magna', 'Tulameen', 'Julia', 'Leo', 'Galante' and 'Terrie Louise'.