I’ve been busy in the garden lately and one of the reasons I’m so busy is that I’m battling a new pest, the bagrada bug (Bagrada hilaris). This new pest made its way to the U.S. recently. It was first found in L.A. County in June 2008. So far in the United States it is only in Southern California and in parts of Arizona. If you live in a northern climate, hopefully you will be spared the spread of this heat loving pest.
I tend a garden in one of L.A.’s hottest microclimates. Even when the mercury is over 100, bagrada bugs seem to do just fine. And unfortunately they love a lot of our favorite garden vegetables such as broccoli, kale and cauliflower. The local nursery says they are destroying the allysum as well. In my garden they have been particularly devastating to an heirloom broccoli raab and some wild arugula. They also are munching the caper plants. Actually, they don’t munch, rather they suck juices out of a plant.
The nymphs are small and resemble a ladybug. Mature bagradas are black with orange markings and look like a beetle. They are often seen in mating pairs. They reproduce quickly and lay their eggs in the soil. Apparently insecticidal soap can help control them but, because they are so new to the U.S., little is known about their ecology here.
I hope some natural predators show up on the scene soon!
I’m trying to control them with diatomaceous earth, soap sprays and organic insecticidal oils. But I’m being really careful about the soaps and oils to be mindful of the bees in my garden.
I think that one of the keys to being a good organic gardener is observation. So I’ve just been watching the bugs, trying to handpick them and wash them off. Diatomaceous earth doesn’t affect the bees, so that is a good thing. It seems to help at least. But after a few days of no beetles, the population seems to explode again. When the populations get too big I’ve been spraying with neem. But I never spray near the flowers that the bees like the best. So it’s quite a challenge, since the bees are all over. I’ve decided to try to spray only after dark now, when the bees have gone to bed.
UC Riverside Center for Invasive Species Research fact sheet on bagrada can be found here.
Mr. Homegrown here: I found one peer reviewed study related to Bagrada hilaris controls, which you can access here. The study found that the most effective treatment is the systemic pesticide imidicloprid which, unfortunately, is also deadly to pollinating insects and is a substance I don’t believe should be on the market. The study did show that starting plants at a cooler point in the season reduced heat loving bagrada bug numbers substantially. Confusingly, Bagrada hilaris is sometimes referred to as the “harlequin bug” which is also the popular name for a similar insect Murgantia histrionica.