Advice for the Home Gardener from the Contra Costa Master Gardener Help Desk
Client's Brussels Sprouts “Problem”
Response and Advice from the CCMG Help Desk:
Thanks for the GREAT picture! You have an "aphid" infestation. Brussels sprouts are in the Brassica family, and this is a very common ailment for that family of vegetables. Most plants can tolerate some aphid infestation but yours has reached a moderate level so you will want to take action.
- Often a forceful spray of water directly on the aphids will knock them off, once they have fallen to the ground most will not be able to climb back up on the plant. Use the water jet option first as it is the least invasive.
- The second action you could employ would be to use a water-soap solution, this would be an insecticidal soap available at any nursery. They are sold in ready to use formulas and in concentrates which must be mixed with water before use. Make sure to follow the directions on the package if you purchase a concentrate.
- For more stubborn infestations you can use a Neem Oil application. Again use the water jet first and then treat any remaining aphids with the Neem Oil.
These products kill primarily by smothering the aphid, so you will need to make sure you cover the infested foliage well, targeting both the top and underside of the leaves. Soaps and oils kill only the aphids present on the day they are sprayed, so you will need to monitor the plant regularly and repeat the application as needed. Keep in mind that any active spray will also kill beneficial insects so spray only when you need to and only the minimum amount you need to get the job done.
The following link is to the UC Davis IPM web site's Pest Note on aphids, it will help you understand the life cycle, good cultural care practices and management options. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7404.html
The good news is you can get this pest under control with some diligence on your part.
Thanks again for contacting us and enjoy those Brussels sprouts.
Contra Costa Master Gardeners Help Desk
Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: firstname.lastname@example.org, or on the web at http://ccmg.ucanr.edu/Ask_Us/