In late summer of last year, a pest showed up in our fields that we had never seen before, attacking kale seedlings and cabbage transplants. A type of Stinkbug called the Bagrada, the pest had been heavily publicized due to its track record of destroying broccoli, kale and cabbage in Southern California fields.
Its seems like long way from the Imperial Valley to Winters, CA for an insect to travel, so we were lulled into a false sense of security. But in our modern world, insects don’t have to move themselves anymore. They get moved by trucks and planes, in shipments of plants and in suitcases. Many of the farmers who grow broccoli in Southern California in the winter grow it in Salinas in the spring and summer, using the same planting and harvest equipment. Last summer the first Bagradas were found on the Central Coast.
Terra Firma and other farms in our area get our transplants from nurseries in Salinas. The Bagradas could have — and likely did — come in on those plants, but they may have also arrived by other means.
The bugs feed on the tiny leaves at the center of small plants, sucking nutrients from them. This causes the leaves to become deformed and stunted. The affected plants don’t die, but they essentially become useless: broccoli and cabbage plants don’t make heads and kale leaves are so deformed that they are not recognizable.
Bagradas continue to feed on plants as they get bigger, but if they make it past a certain stage, it doesn’t cause the same type of damage. Last year we lost only a small percentage of our brassica crops to the bugs. After panicking when we found them in our fields, we were relieved that the damage was not as bad as we expected.
This year the damage is much more extensive. Clearly, we started the season off with far more Bagradas emerging from the soil due to their colonization last year. In our cabbage field, for example, it looks like they have already damaged about a third of the plants — meaning we will harvest 33% less crop. It’s likely been exacerbated by the absurdly warm weather we’ve been having: temperatures since we started planting brassicas in mid-August have been averaging 10 degrees above normal almost every day.
Bagrada bugs feed and breed more in hot weather. And they are not shy about it. Right now on our cabbage plants you can find adult couples breeding actively right alongside babies, toddlers and teenagers feeding. When — if — colder, wetter weather arrives, they will migrate into the soil where they will hibernate until next summer.
Organic growers face a huge challenge with this pest. There are no organic materials that are effective at controlling Stinkbugs, and the Bagradas are no different: we can’t kill them. And conventional growers are now using far stronger insecticides to grow brassica crops in order to control the bugs.
Altogether, broccoli, cabbage and kale represent probably a quarter of all the crops we put in your CSA boxes in the winter. So we are very concerned about our future ability to grow them.
Sometimes pests like this control themselves, by overpopulating and then crashing. But because the Bagradas are an invasive species, this is less likely to happen. In the short-term, our best hope is for this year’s El Niño to switch to La Niña next year, ushering in a colder winter that might slow the Bagrada’s destructive lifecycle.
Years ago, we abandoned growing certain types of winter squash due to damage from another highly specific pest that became established on our farm — the Squash Bug. Over the course of ten years, scientists identified a fly that parasitizes the bugs, and then released the flies throughout Northern California. Eventually the parasite was successful at bringing Squash Bug populations under control, and this year we successfully grew some of the squash varieties that we had previously given up on.
In the long-term, the best hope to control the Bagrada will be from this type of “biocontrol”. Researchers are currently searching for an effective predator species from the insect’s native habitat (Asia) that they can successfully introduce here. We hope they will find one soon.