Blackcurrant bushes are generally health blackcurrant powder. However they are sometimes attacked by insects and diseases and this article aims to identify the causes and how to treat them. As far as size goes, birds are definitely the largest pest to affect blackcurrants. They are attracted to the developing fruit and destroy them completely.
The aphids also create a sticky liquid which cover the leaves and attracts other insects and diseases. They rarely kill blackcurrant bushes but can seriously reduce the amount of fruit produced. See our detailed article on identifying and dealing with aphids here. One particular aphid can cause red blisters and marks on the surface of the leaves on all the currant bushes. This particular aphid tend to restrict itself only some of the leaves and although the effect looks dramatic it rarely affects the health of the plants. If you want treat it then do as described for aphids above. Aphids, including the Currant Blister Aphid, are first seen on currant bushes from late April to mid May depending on the climate in your area.
If you do intend to spray them, do it at the very first sign of damage for maximum effect. Big bud mite almost exclusively affects blackcurrant bushes. In late winter, January and February time, when the buds would normally begin to form, they do so but are much larger than normal. Affected buds either fall off or produce distorted growth which fails to produce fruit. Reversion Disease affect blackcurrant bushes almost exclusively.