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Sap-sucking aphids are problematic for currant bushes. In spring, they cause the foliage to become blistered and puckered, as well as discolouring areas, leaving yellowish-green or red patches. The aphids then fly to hedge woundwort, a wildflower, for the rest of the summer, but return to the currants in autumn to lay their eggs. Since the currant crop isn't affected, action isn't essential.
Solution
Organic
If the symptoms were evident last summer, in winter get rid of the eggs by spraying plants with an enzyme wash, which will quickly dissolve them.
Chemical
In spring, spray plants with the systemic insecticide thiacloprid or pyrethrumn to kill the emerging aphids. Don't wait for the symptoms to appear, as there's no point in spraying once the leaves have become puckered.
