Cole crop producers in the San Joaquin Valley should be on the lookout for a new, exotic pest called the Bagrada bug. This stink bug, also known as the painted bug or harlequin bug, was first found in California in 2008 and has since become a pest of cole crops in the Imperial and Coachella Valleys of California, as well as in southwestern Arizona. The Bagrada bug is native to Southern Africa, and can also be found in Southern Asia and Southern Europe. In these locations it is a significant pest of a broad range of cole crops such as cabbage, cauliflower, broccoli, kale, turnip, mustard, and radishes.
Bagrada bug feeds by sucking plant juices through straw-like mouthparts that it inserts into the plants. When young seedlings are attacked, feeding at the growth terminal can cause branching such that multiple heads are formed on crops like broccoli and cauliflower. This renders the crop unmarketable. On older plants, wounds made by the bug’s mouthparts gives the plants a stippled, and then scorched, appearance.
Farmers that are currently dealing with this pest have been forced to utilize broad spectrum insecticides, primarily pyrethroids, to try to knock back populations. While this is not an ideal situation, at least it has allowed the pest to be managed such that crop losses can be averted. However, pyrethroids are not an option in organic fields, and organically-acceptable pesticides such as permethrin, spinosad, and a wide range of oils and not effective. For this reason, the greatest level of damage has resulted in organic fields and in both community and residential gardens.
One of the reasons for the successful invasion of Bagrada bug is its preference for the same cool weather that allows Californians to produce cole crops. This means that it is most likely to be found in the fall through early spring in California’s southern deserts and in the San Joaquin Valley: if found in coastal California areas, it could potentially become a problem all the way through the summer.
Bagrada bug can be identified by the distinctive black, white and orange markings on the shield-shaped backs of the adults. They are very similar to what we commonly refer to as harlequin bugs, but are about half the size. Nymphs are more variable in color and range from white when very young, to red with dark markings as they mature. Eggs are barrel-shaped, range from white to red depending on maturity, and can be found in clusters either in the soil or on leaf material touching the soil.
Growers or pest control advisors who find Bagrada bug outside of California’s southern deserts are encouraged to contact a farm advisor at their local UC Cooperative Extension office, or report it to the local agricultural commissioner.