Stinkbug Invasion

Sep 01 2010 Published by under Biology & Environment

Healthy Sweet Alyssum

One of my favorite flowering plants is Sweet Alyssum: it's low maintenance, heat and drought tolerant, and flowers year-round (at least here in Southern California).  Since it grows low to the ground, it makes a nice addition to the pots with seasonal bulbs, which would otherwise just be bare dirt for a good part of the year.

Because Sweet Alyssum is usually so easy to grow, I was a bit surprised to see that in several of my pots it was starting to look dried out and sickly. Even though there was a heat wave last week, my other potted plants look just fine, so lack of water was unlikely to be the problem.

On closer inspection of one of the plants, I noticed that it was swarming with little red beetles. My first thought was "Yay, ladybugs!",  since they are great for controlling insects pests like aphids.  But when I looked a bit closer, I noticed their markings were more ornate than the simple red-with-black-spots of ladybugs. And while the bugs were teeming on the Sweet Alyssum, other nearby plants appeared bug-free. What could they be?

Painted Bug (Bagrada hilarus) eating my Alyssum

Painted Bug (Bagrada hilarus) eating my Alyssum

After a bit of research I identified the critters as the Painted bug (Bagrada hilaris) or Bagrada bug, a type of stinkbug. It is an invasive species native to East and Southern Africa that first appeared in Los Angeles County in June 2008. Last year it reached the inland low desert. And now it's widespread in Southern California and western Arizona.

Bagrada bugs primarily eat Brassicaceae, a family of plants that includes cruciferous vegetables such as cabbage, mustard, broccoli, cauliflower, radish, turnips, and kale.  Sweet Alyssum is an ornamental Brassicaceae, which explains why those plants (and only those plants) were infested.

Unfortunately Bagrada bugs are quite hardy, and resistant to most organic methods of control. According to the UC Riverside Center for Invasive Species Research the heaviest Bagrada infestations are in "organic farms, community gardens and residential vegetable gardens where little or no pesticides are used."  The easiest way to control them without pesticides is to remove the infested plants, cultivate the soil to kill the unhatched eggs, and squash any bugs that remain.

Lots of stinkbugs!

So that's what I've done. All my Sweet Alyssum is gone.  Fortunately I'm not growing any other members of the mustard family, and there aren't any reports of the pests attacking tomatoes or eggplant or zucchini or the remaining ornamental plants I have growing in my yard.

I probably won't try to grow any related plants in the future, since we live adjacent to a field with mustard plants growing wild. A natural reservoir for the pest.

But while my garden will easily recover, the rapid spread of Bagrada bugs has the potential to be a serious problem for Southern California's organic farmers. Hopefully, they won't end up on the state's 10 most (Un)wanted list.

All photos on this page by me. Click to see larger images.

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4 responses so far

  • Hi - I am visiting from CotS. Pretty little bugs, but what a big problem! Non-native species always upset the ecosystems they inhabit...sorry you had to give up your fave alyssum.

    • Peggy says:

      Fortunately these little stinkers are picky eaters. One year I had a bunch of grasshoppers, and it seemed like they would eat anything (and everything).

  • Holly says:

    Thank you for this explanation - I have exactly the same problem! I'll be tearing out my alyssum too and holding off planting other Brassicas.

  • James Tamer says:

    Los Angeles 90042 here.
    I have a similar species of stinkbug. After killing all the arugula, Brassicas, mustards, lettuces, they are now eating the tomatoes. They are smart enough to eat only the tomato fruit and not the leaves or stems which are poison. Darn them!