Brussels Sprouts Aphids: Gray Aphids in the Sprouts plus Control

Brussels sprouts aphids are almost always cabbage aphids. UC IPM notes they are greenish gray with a white waxy coating, form dense colonies plus are often found deep within the heads of Brussels sprouts plus cabbage.

The short answer

Cabbage aphids cluster in waxy colonies inside sprouts plus curled leaves. UC IPM advises scouting at least twice a week after transplanting. University of Idaho Extension advises water sprays plus pruning infested leaves when colonies are local. Lady beetles, lacewings, syrphid larvae plus parasitic wasps lower numbers when broad sprays are avoided.

How do you spot cabbage aphids?

UC IPM notes cabbage aphids prefer the youngest leaves plus flowering parts. Winged adults show a black thorax. Idaho advises looking for lady beetles, lacewings, syrphid fly larvae plus aphid mummies while scouting, since mummies show parasitoids are at work. University of Minnesota Extension notes white cast skins on leaves or in honeydew.

Why are aphids hard to clear from sprouts?

UC IPM notes leaves curl around the dense, waxy colonies, so aphids are hard to reach. Infestations on Brussels sprouts can start in seedling beds, it notes. Minnesota notes cabbage aphids can complete up to 15 generations a season because they mature quickly. UC IPM notes the aphid feeds only on plants in the mustard family, including weedy mustards.

Source: UC IPM, University of Idaho Extension plus University of Minnesota Extension.

How do you control aphids on brussels sprouts?

Idaho advises avoiding broad spectrum sprays so natural enemies hold aphid numbers down. It advises hard sprays of water to knock aphids off, plus pruning out infested leaves. It advises seedling covers for young plants plus checking nearby weeds such as mustards before planting. Minnesota advises flowering plants that bloom at different times to draw natural enemies. UC IPM advises hedgerows as their refuge.

University of Illinois Extension notes some gardeners remove the lowest six to eight leaves as sprouts develop, which opens the stalk for scouting.

How to: step by step

1. Clear weedy mustards near the bed before planting.
2. Cover seedlings while young.
3. Scout twice weekly from transplanting.
4. Look inside lower sprouts plus curled leaves.
5. Hose off colonies on sturdy plants.
6. Prune out leaves with local colonies.

Troubleshooting

Gray waxy clusters inside sprouts: cabbage aphids. UC IPM notes they hide deep in heads.

Aphids return fast: many generations. Minnesota notes up to 15 a season.

Few lady beetles: broad spraying. Idaho advises avoiding them.

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Sources

• Cabbage aphid, cole crops, UC Statewide IPM Program (UC ANR)
• Aphids in gardens, University of Idaho Extension
• Aphids in home yards and gardens, University of Minnesota Extension
• Brussels sprouts (home vegetable gardening), University of Illinois Extension