Hunting for good bugs to fight bad bugs
Mark Hoddle waits for the door to click into place. A magnetic sensor won’t let him open the next door, just an arm’s length away, until the first has been sealed shut.
Then he’s walking through a maze of darkened corridors. Black lights — positioned to lure and then zap any fugitive bugs — cast a dim lavender glow that suggests rather than reveals the way forward.
Finally, Hoddle reaches a high-security laboratory. Inside, behind a wall of glass, his wife and fellow entomologist, Christina, hunches over a microscope. Ornate green earrings from Pakistan, picked up on a recent parasite-hunting expedition, dangle above the lapels of her lab coat.
When Hoddle raps on the glass, quarantine officer Imad Bayoun stops him: The alarms could go off.
Christina, looking up, brandishes a vial the width of a pinkie.
“See that little black speck?” Hoddle says. Trapped inside are tiny parasitic insects that the couple traveled halfway around the globe to find.
California, like many other states, is under attack by insects from foreign lands that destroy crops, prey on native plants and compete with indigenous creatures for food and shelter. They cost the U.S. about $20 billion annually in agricultural losses, environmental damage and pest control.
“Each year, California acquires at least six new exotic species. At least six,” said Hoddle, 44, director of UC Riverside’s Center for Invasive Species Research.
They arrive on ships, in produce, on unsuspecting humans and animals. Many are harmless, but some wreak havoc, often because they’re no longer held in check by parasites that afflicted them in their native habitats.
That’s where entomologists like the Hoddles come in. They believe the solution is to make life miserable for invasive critters by importing their natural enemies. It’s an approach called “biological control,” and it has taken the couple around the world in search of exotic parasites, which they bring home in Rubbermaid containers. They’ve grown accustomed to grillings by airport security officers.
Much about their life mirrors their professional obsession. They were married six years ago at the Mission Inn in Riverside, where California entomologist Harry Scott Smith coined the term “biological control” in 1919. Paintings of insects adorn the walls of their home. They keep a mealworm colony in their kitchen to feed orioles and lizards in the backyard. Christina, 36, drives a bright yellow VW Beetle, though the couple bikes to the university’s quarantine facility each day.
The complex, with gleaming greenhouses on each level, looks distinctly modern from the outside. Inside, it’s a warren of trick doors and rooms within rooms designed to securely hold insects until they’ve been thoroughly studied.
“Anything that goes into that building can’t escape,” Hoddle said.
At least not until the Hoddles have the all-clear to unleash a pest against its enemies.
Insects are among the most troublesome of invasive species. They multiply quickly, can travel far and are hard to detect. Controlling them with pesticides is costly because the chemicals have to be sprayed on crops every season. Pesticides can’t be used in uncultivated areas because they would kill all bugs, good and bad.
California, Hawaii and Florida are especially prone to insect invasions because their long coastlines and mild weather attract trade and tourism.
“They do well for the same reasons we like living here,” Hoddle said of the interlopers. “Great climate, pretty much all year-round; lots of food. And, most importantly, they’ve escaped their natural enemies.”
Finding those enemies isn’t easy. First, the Hoddles have to figure out where a pest came from. Then they have to go there and find it. The final step is to identify parasites that prey on the offending bug and bring them back to UC Riverside for study.
With funding from the state and federal agriculture departments and the citrus industry, the Hoddles have traveled to Pakistan’s Punjab province several times, most recently this year, looking for natural enemies of the Asian citrus psyllid. The bug has been sucking the fluids out of citrus trees in California since 2008 — and spreading a bacterial disease known as huanglongbing (Chinese for “yellow dragon disease”) through Florida.
In studying the problem, Mark Hoddle came across an obscure 1927 paper in which researchers reported finding parasitic wasps that fed on the citrus psyllid in Punjab, which has a climate similar to that of California’s citrus-growing regions.
In Pakistan, the couple spent hours tramping through citrus groves in triple-degree temperatures, armed with pruners, scissors and soda-bottle crates in which they placed vials stuffed with snipped branches. At night, they brought promising insects back to a local lab. Frequent power outages cut off the lights and ventilation. The Hoddles would pull out headlamps and continue peering into microscopes as sweat rolled off them in the dark.
They flew home with a Rubbermaid box full of specimens of two kinds of stingless wasps that prey on the psyllid.
Alarms buzzed when Mark’s passport went under the scanner at London’s Heathrow Airport on the way back to Los Angeles. This wasn’t unexpected: The couple had told security officials about their cargo ahead of time. After probing questions, they were allowed to board the plane. Their sealed container, full of hundreds of insects, sat above them in the overhead bin.
After further questioning at LAX, the pair rushed to the UC Riverside quarantine facility, where they deposited the insects on laboratory plants to get them breeding.
They hope the newly discovered parasitoids (the technical term for parasitic creatures that ultimately kill or sterilize their hosts) will help eradicate the citrus psyllid as successfully as another critter wiped out the glassy-winged sharpshooter in French Polynesia six years ago.
The sharpshooter, native to Mexico and the Southeastern United States, exploded in numbers after arriving in California in the 1980s, infecting crops with a bacterial blight called Pierce’s disease.
In 1999, shipments of ornamental plants, probably from Southern California, accidentally took the sharpshooter to French Polynesia. The insects — which can suck 100 times their volume in fluids in a single day — soon blanketed plants all over Tahiti. Their waste fell from trees like rain, baffling passersby. In some parts of the island, 300 of the insects could be picked off a single hibiscus plant in a minute.
Hoddle and his colleagues released a parasitic wasp from their collection into the wild there. The wasp preys on the sharpshooters by laying eggs inside sharpshooter eggs; these then hatch and eat the sharpshooter eggs from the inside out.
Within seven months, the sharpshooters had practically vanished from French Polynesia. “We were like rock stars in the newspapers,” Hoddle said.
“Bye-bye, peeing fly,” a newspaper headline crowed in French.
As the sharpshooter populations plummeted, so did the newly introduced parasitoids. Now, Hoddle said, “they just play hide-and-seek around the island.” That’s the beauty of biological control, he said — the two populations keep each other in balance.
Despite such successes, some scientists express concern about opening the Pandora’s box of pest-on-pest combat. Peter Stiling, an ecologist at the University of South Florida, cites the case of the weevil Larinus planus, which was released in Western and Midwestern states in the 1990s to control the invasive Canada thistle. It ended up feeding on a rare thistle native to Colorado and Utah as well.
And then there is the case of the cactus moth, whose larvae eat the prickly pear, a cactus from the Americas that has invaded other parts of the world. After the moth was released in the Caribbean in the 1960s to control the prickly pear, it spread to the Florida Keys and fed indiscriminately on native cactuses, reducing one to near-extinction, Stiling said.
“It’s like releasing the genie out of the bottle,” he said. “You can never get it back in.”
Hoddle is aware of such “friendly fire” risks. “We don’t want our good guy to wipe out another good guy,” he said.
That’s why all waste products in the UC Riverside testing facility are cooked for days, why whole floors between each level are dedicated to plumbing and electricity so that maintenance workers never enter testing floors, and why every inner room has slightly less air pressure than adjacent rooms, so that any AWOL bug will get sucked back in, Hoddle said.
Fellow UC Riverside entomologist Raju Pandey wears a bodysuit and hood when working in the facility’s highest-security levels — and then takes further precautions. He fashions discount ladies’ nylons into wrist guards to keep insects from hitchhiking out of the building under his sleeves. He uses only white or brown nylons, so that stray bugs will be visible.
The Hoddles and coworkers are now testing their Punjabi wasps on the citrus psyllid during long hours in the high-security quarantine. It is a grueling process. They grow trees, in pots, on which the insects are bred. Then they sic the parasitoids on them.
They grow more trees, breed more insects and test them again, and again.
“Bugs don’t take weekends,” Christina Hoddle said, “so neither do we.”
If the tests pass muster with the U.S. Department of Agriculture and the North American Plant Protection Organization, which sets standards for the U.S., Canada and Mexico, the tiny wasps should be ready for release at sites in Los Angeles County early this winter.
But until the parasitoids prove their worth, the scientists are stuck with their captives in rooms within rooms, behind walls of glass and metal.
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