Somewhere in Africa, a man gets on a plane bound for California. He has visited several friends and relatives just before leaving, collecting letters and other items from them. Once here, he again visits friends and relatives, delivering the letters and packages. At each stop, tiny visitors are left behind. They multiply and thrive for a while without being noticed, until they begin to cause major devastation.
No, I’m not talking about the terrible Ebola virus. In this case, the plague from Africa happens to be an insect called the Bagrada bug. Bagradas first showed up in Southern California four years ago, when broccoli farmers discovered them in their fields. They had most likely arrived several years before into Los Angeles airport in the baggage of a traveler from Africa.
Bagrada bugs are “stinkbugs”, hard-shelled, fast moving critters that are known for three reasons: they damage crops; they are extremely difficult to kill with pesticides, especially organically; and they smell bad when you crush them. What stinkbugs are not generally known for, however, is reproducing quickly and abundantly. The stinkbugs that are native to California tend to be low-level pests because there are rarely lots of them in a single field.
Bagrada bugs reproduce quickly — every five days or so — and prolifically. They feed on a large number of plants including edible and ornamental crops, but their favorite food by far are brassicas or cole crops. These include kale, broccoli, cauliflower, cabbage, arugula, mustard and brussel sprouts. They don’t actually munch on the leaves, but rather suck out their juices. Small plants often die when they do this; larger plants end up deformed. For example, cabbage or broccoli that has been attacked by the bugs does not make heads. When the weather is warm, bagrada bugs can wipe out entire fields — and they have.
Roughly half of the crops that we plant in the fall and harvest in the winter at Terra Firma are cole crops. So you can imagine how we felt in late August when we discovered bagradas sucking on and killing our first planting of kale. At first we thought the black and red Bagradas were Ladybugs, which help control aphids in brassica fields, and which they ironically resemble. Another bit of irony: it also turns out that the flowering allysum that we have been planting this year to attract beneficial insects to our fields also attracts the bagradas.
The bugs most likely arrived at our fields as hitchhikers on the broccoli and cabbage plants that we buy a nursery in Gilroy. If the insect was a pest of a different, more widely planted crop — say, almonds or grapes — a quarantine would be in place to keep them from spreading in this way. But with just a few (dozen thousand) acres of brassicas planted in California, state agriculture officials decided the expense was not worth the effort. Instead, they are already working on identifying potential biocontrol agents — parasites that target the Bagrada specifically and which could be released to control them.
Our broccoli and cabbage season is just beginning, and near as we can tell, the African attacker seems to be taking about a 10% toll or less on the crops. There’s not much more we can do other than wait and see whether the populations of the bug get bigger and more destructive next year — all our fingers and toes are permanently crossed already.