Pests That Attack Black Currants
- Imported currant worms are spotted caterpillar-like worms that grow to a length of 3 inches. They feed on black currant foliage and can completely defoliate a plant. The adults are small sawflies. Each year, adult females produce two generations of young, the first in spring and the second in late summer. Look for the eggs on the undersides of the leaves, along the veins. Control imported currant worms by removing and destroying infested leaves. Use insecticides containing malathion or rotenone as soon as you notice the larvae.
- Currant fruit flies lay their eggs inside developing black currant fruit. Fruit with red spots surrounded by dark areas contain the small, white fruit fly maggots. Remove and destroy infested fruit on the bush as well as the currants that fall to the ground. Apply insecticides containing malathion or rotenone as soon as the fruit begins to develop, making two applications 10 days apart.
- Currant borers and stem grinders are worm-like larvae that feed on the pith inside black currant stems. The adult currant borer is a blue-black moth with clear wings and yellow markings. The adult stem girdler is a sawfly. Sickly growth and dying canes indicate that the larvae are feeding inside the canes. Since the destructive larvae of these insects live inside the stems, contact insecticides are ineffective. Cut off the canes about 8 inches below the damage and burn them.
- Currant aphids and fourlined bugs feed by sucking sap from a black currant plant. While the tiny green aphid sits in one place most of its life, the yellow- and black-striped fourlined bug is active, running and flying around the plant. Both of these insects cause distorted and discolored foliage, and when they are abundant, the plant fails to thrive. Use insecticidal soaps or dormant sprays against aphids, and insecticides containing malathion against fourlined bugs.
San Jose scale is a tiny, disc-shaped sucking insect that feeds by sucking sap from the canes. These insects stay in one place their entire adult life. They are covered with a hard shell that is impermeable to insecticides. Dormant oil sprays are the best method of control.