A Tiny Pest, a Big Crossroads for California Citrus | Civil Eats

A Tiny Pest, a Big Crossroads for California Citrus

Citrus greening disease hasn’t officially hit the state yet, but farmers may be required to cut back on the use of neonicotinoids, the main tool used to control the pest that carries it, because of its impact on pollinators.

Guy Davies, an inspector of the Florida Division of Plant Industry, shows an orange that is showing signs of

Jim Gorden stops his truck at the edge of one of his orange groves in Tulare County in the foothills of California’s Sierra Mountains. After 50 years as a citrus grower and pest control advisor in the San Joaquin Valley, the 81-year-old is “mostly” retired, but still vigilant about pests that may harm his fruit. A yellow sticky trap, about the size of a birthday card and speckled with insects, hangs from a branch. He leans in, eying each insect closely. None appear to be the Asian citrus psyllid, an invasive pest that poses the biggest threat to citrus growers in California.

Jim Gorden inspects a sticky trap for asian psyllids. (Photo by Anne Marshall-Chalmers)

Jim Gorden inspects a sticky trap for asian psyllids. (Photo by Anne Marshall-Chalmers)

Gorden is relieved. About crumb-sized and the color of dusty farmland, the psyllid carries a bacterial disease called huanglongbing (HLB) or “citrus greening disease,” which destroys fruit and kills trees. The disease has wreaked havoc on Florida’s citrus industry over the last decade and California citrus growers are on heightened alert.

Though citrus greening has not yet been discovered in commercial orchards in California, Gorden and other growers feel it’s only a matter of time. Last year, an unusually high number of psyllids were detected in nearly 120 locations around the San Joaquin Valley, home to about 80 percent of the state’s 267,000 acres of citrus. And this winter, a time when psyllids typically die off in the valley, three separate detections occurred.

To kill off psyllids and avoid the possibility that a roaming, infected psyllid could spread disease, most growers treat their groves with a widely used but controversial class of insecticides—neonicotinoids or “neonics” for short. In one year alone, California citrus farmers applied (or more likely had their workers apply) nearly 55,000 pounds of the neonicotinoid imidacloprid.

Beneficial insects, like honeybees and butterflies, inadvertently take up neonics through pollen and nectar. Research shows the systemic insecticides harm pollinators, lowering their immune systems, dimming their navigational skills, and weakening their ability to reproduce. That’s important because about 75 percent of the world’s flowering plants and 35 percent of the world’s crops depend on those pollinators.

But California may soon be one of the first states to drastically limit the use of neonics in agriculture. Last year, the state released a draft proposal that would require citrus growers to essentially cut their use of imidacloprid by about half the label rate. Furthermore, growers could only apply the pesticides once a year, down from the current three to four applications. While some states have pulled neonics from retail stores to curb their use in home gardens, California’s proposed action would be among the most restrictive in the nation, significantly limiting the overall quantity used. “It’s huge,” says Jen Sass, senior scientist at the Natural Resources Defense Council (NRDC), an advocacy group that has pushed for a complete ban on neonics.

California’s department of pesticide regulation (CDPR) is scheduled to release an updated proposal restricting the use of pesticide this fall, with formal adoption scheduled for late 2021 or 2022. And while there are other tools to combatting psyllids— predator bugs that target them, organic sprays, and protective netting that blocks the pests from accessing trees—these alternatives can be pricier and not as long-lasting as neonics. For this reason, many farmers and pest control advisors are pushing back. The agency has received nearly 9,000 emails, letters, and voicemails in response to the suggested cuts. In written comments and during public forums, farmers and others in the industry have called the quantity of neonics they’d be permitted under the suggested guidelines, “worse than worthless” and “overreach.”

The Psyllid’s Curse

When left unmanaged, psyllid populations balloon rapidly, allowing them to become super-spreaders of citrus greening, which originated in China more than a century ago. As the name implies, the disease turns fruit green, bitter, and misshapen.

The pests feast on plants with piercing, sucking mouths that function like something between a needle and a straw. If the psyllid carries HLB, it can pass the pathogen from its gut to the tree while eating, and that can be fatal for the tree.

“It’s a pretty nasty vector,” says Matt Daugherty, a cooperative extension specialist at the University of California, Riverside. “Their populations can get roaring pretty quick.” A female psyllid can lay 500 to 800 eggs. In a sinister twist, psyllids that do not carry HLB are attracted to infected trees, Daugherty says, conversely those that are infected tend to prefer healthy, uninfected trees. And in California, citrus is everywhere, with trees lining farmland and dotting residential yards. “That’s bad luck on our part,” he says.

In the late ‘90s, psyllids arrived en masse in Florida. Since then, the amount of citrus acreage growing fruit has dropped by roughly half.

Gorden, who has white hair, a mustache, and an unfussy, gentle manner, believes HLB in California orchards could prove even more devastating than what unfolded in Florida. Florida citrus is used primarily for juice, meaning that the fruit doesn’t have to look perfect. California’s $2 billion industry produces bright, whole table fruit. The San Joaquin Valley alone grows about 4 million tons of citrus every year. “We live by the quality of our product,” Gorden says.

A Useful Tool

The first Asian citrus psyllid in California was discovered in August 2008 in San Diego County. A few days later, Gorden met with other citrus industry leaders. At the time, Gorden was vice chair of California’s citrus research board, a grower funded organization.

A keychain with four psyllids encased in plastic. Gorden uses this to show growers what the psyllid looks like. (Photo by Anne Marshall-Chalmers)

A keychain with four psyllids encased in plastic. Gorden uses this to show growers what the psyllid looks like. (Photo by Anne Marshall-Chalmers)

That year, the California Department of Food and Agriculture (CDFA), scientists and citrus leaders started building a multi-pronged approach to control psyllids and prevent the spread of HLB. Sticky traps, like those in Gorden’s grove, help monitor their whereabouts. Tarps on trucks carrying citrus restricts psyllids from drifting off loads and easing into orchards. Neonics and other pesticides, meanwhile, provide what Gordon calls the muscle to “knock ‘em down.”

According to the CDFA, the psyllid’s presence in California has caused a significant ramp-up in the use of neonicotinoids in orchards over the last decade. A soil-application of imidacloprid, usually in late summer, moves up into the plant’s stems, leaves, and flowers, ensuring nymphs and adult psyllids that feed on new growth will encounter the toxins. The neonics stay in the plant’s system for several months, providing lasting protection from pests. According to a recent CDFA evaluation of neonic use in California, under the proposed guidelines, farmers would have to abandon routine soil applications as the permitted amount of imidacloprid wouldn’t be effective.

Growers also rely on foliar applications of neonics, both before harvesting fruit and when psyllids appear in groves unexpectedly. Growers can also use a class of insecticides known as pyrethroids. Should the use of neonics be restricted, growers worry over-relying on pyrethroids may result in pests that build resistance to the chemicals.

In 2014, the California state legislature required CDPR to determine what risk neonics posed to honeybees and other pollinators, and to follow up with mitigation measures by 2020.

The CDPR partnered with the Environmental Protection Agency (EPA) and Canada’s pest management agency on a number of studies assessing the impact on bee colonies from exposure to four different neonicotinoids in hopes of determining a level of exposure that bees could tolerate. The agency then compared those levels to residue levels typically found on pollen and nectar in fields, with extra scrutiny given to crops that are highly attractive to pollinators, such as nuts, apples, and citrus. CDPR determined the amount of neonics currently allowed on certain crops was too high, and this past fall issued the proposal limiting usage to a wide range of crops.

Frustrated citrus growers have pointed out that last year, during the Trump administration, the EPA used the same suite of studies as CDPR and issued an interim decision that greenlit five of the most popular neonics with minimal restrictions. One reason, says Lucas Rhoads, a NRDC staff attorney, is that when analyzing risks like pollinator health and groundwater contamination versus the economic benefit farmers gain by using cost-efficient neonics, Trump’s EPA “emphasized the benefits but downplayed the costs.”

‘A Bunch of Bums’

Bees visit citrus orchards as their perfume-y, white blossoms open to collect nectar and pollen for food, and in turn create a distinct, light golden orange blossom honey. Citrus trees don’t need bees, as they self-pollinate, but they play a vital role in much of California agriculture.

According to the Pollinator Stewardship Council in Colorado, about 90 percent of the country’s commercial honeybees travel to California in the winter for almond pollination.

Over the last 15 years, beekeepers have reported dramatic colony loss, occasionally as high as 40 percent. From January to March, when California is home to more than a million colonies, anywhere from 170,000 to 230,000 of those colonies will collapse, according to recent U.S. Department of Agriculture (USDA) surveys. Dan Raichel, a staff attorney with NRDC, says neonic use exploded in the mid-2000s, around the same time colony losses spiked. “Research has long indicated this is more than a coincidence,” Raichel says.

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Developed in the ‘90s, neonics were offered as a safer alternative to more toxic organo-phosphate chemicals. Applied to corn, cherries, lettuce and many other crops, neonics are now the most widely used insecticides in the world, representing 25 percent of the insecticide market.

In California, neonic use has exploded, growing 70 percent between 2007 and 2016. David Bradshaw, a second-generation beekeeper in Tulare County, says he knows when his honey bees have been exposed. “They turn into a bunch of bums,” he says. “(Neonics) don’t kill them outright but it messes with their navigation, their foraging.”

Research has shown neonics also harm aquatic invertebrates and grassland birds. Last year, medical experts and scientists sent a letter to the EPA urging more research into possible developmental harm to humans from repeated exposure to neonics through food and groundwater. The coalition requested a ban on neonic-treated seeds, a currently unregulated practice of coating corn, soy, and other seeds with the insecticide.

Bradshaw, who is tall with floppy brown hair, glasses, and a weary grin, has been a beekeeper for 40 years and says it’s getting harder every year. Habitat loss and the Varroa mite contribute to colony loss, but he says widespread neonic use shares the blame. “This stuff takes on a life of its own,” he says. “It’s in the soil, in the rivers. There were things that were more toxic, but they sprayed them on plants, then you waited three hours and it was gone. It doesn’t affect the bees anymore.” But neonics linger; they’re in the plant’s circulatory system for months on end.

Another Way?

On a sunny morning in Exeter, California, Seth Tillery walks through his 10-acre organic citrus grove. His two barn cats—Slim and Sister—follow him, slinking around Valencia and navel orange trees as if playing hide-and-seek.

Tillery grew up surrounded by citrus; his dad transported it, his mom worked in the administrative offices of Sunkist. His decision to try organic came after working with organic growers on the marketing and packing side. “I was raised to spray it, kill it, and not worry about it,” Tillery says.

A ladybug on Jim Gorden's farm. (Photo by Anne Marshall-Chalmers)

A ladybug on Seth Tillery’s farm. (Photo by Anne Marshall-Chalmers)

Instead of neonics, Tillery wards off psyllids and other pests by relying on horticultural oils combined with products containing potassium salts of fatty acids or potassium silicate. He recently started using a spray made from the extract of garlic and cinnamon. “The effectiveness of it is like 48 to 72 hours and then it will kind of dissipate,” he says. Because organic methods are so short-lived, growers must apply them far more frequently than conventional pesticides. “It costs me 20 to 25 percent more to grow [citrus] organically than conventionally,” Tillery says, adding that the cost is offset by his fruit’s higher price.

Tillery is not opposed to conventional growing, but he’s excited by the “ecosystem” he’s created. He places large ceramic pots of roses around his property to lure beneficial bugs. “Look at that,” he says, pointing to a ladybug on a tuft of leaves. “That’s what we want. They’ll go after little pests.”

In 2012, a tiny parasitic wasp called the Tamarixia radiata was introduced to California from its native Pakistan to help control psyllid populations. The wasps eat nymphs and, sometimes, parasitize them by laying eggs on their waxy, miniscule bodies. CDFA releases millions of tiny parasitic wasps every year, primarily in southern California. The wasps have helped control psyllids in residential settings, decreasing the likelihood that rogue backyard populations will wander to commercial groves.

On agricultural land, however, it’s up to growers to decide how they manage psyllids. “[The wasps] are too expensive to be used like an insecticide,” retired farmer Jim Gorden says. And introducing wasps into commercial groves where neonics are used could harm or kill them.

Chemical companies traditionally respond to regulation by swapping one insecticide for another. For a long time, strawberry growers in California relied on methyl bromide to control soil-borne pathogens and weeds. When that chemical was phased out due to its impact on the ozone layer, most growers simply turned to chloropicrin and other fumigants as replacements. Growers, like Gorden, are expected to deliver a low-cost piece of fruit that looks impeccable. “The ugly stuff gets left behind,” he says. Insecticides offer a cost-efficient route to achieving that goal, the cost often playing out over time.

But Jen Sass with NRDC wants to see wide-scale change in response to the potential phase down of neonics in California. “The solution should not be another chemical,” she says. “And farmers need help to get there.”

Jessica Shade, director of science programs at The Organic Center, a Washington D.C.-based nonprofit dedicated to researching the benefits of organic farming, says she’s hearing from conventional citrus farmers seeking to incorporate methods beyond neonicotinoids, and it’s not just because of possible regulations.

“Because those pesticides have been used at such high doses and so frequently, it’s accelerated the selection process for psyllids who are resistant to pesticides,” she says. In other words: with a life cycle that only lasts a few months, psyllids can quickly evolve to resist the toxins. And yet, the transition to organic can be difficult. Farmers must stop using synthetic fertilizers or pesticides three years before they can achieve certification, and the change can lead to lower yields.

Last year the USDA funneled $45 million to a number of research facilities studying non-chemical techniques for protecting citrus trees from psyllids and HLB. A research team at the University of Florida’s Institute of Food and Agriculture Sciences, for instance, is working on creating a transgenic or genetically engineered tree that could be resistant to the disease.

There are also hopes of finding an HLB vaccination for trees, or effective therapeutics, such as an injection or spray of an antimicrobial peptide found in Australian finger limes that reduces the pathogen’s presence in citrus trees. In Florida, planting cover crops that improve soil health and, in turn, a tree’s ability to fight off citrus greening, is showing promise. Scientists in Florida and California are also focused on selective breeding to create trees that are naturally resistant to the infection, but that solution is likely years, maybe decades away. And Gorden says it’s only a matter of time before HLB hits commercial groves in California.

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An Urgent Threat

In a lemon grove outside of Moorpark in Ventura County, a German shepherd runs alongside a row of trees. A handler in sunglasses keeps pace. The dog suddenly halts mid-row and sits at the base of a tree, still as a statue, awaiting a reward. The dog is trained to detect the scent of the bacterium that leads to HLB.

It’s July 2019, the leaves of the tree the dog has identified will be sent to a lab and tested for the HLB infection. The result? Negative. HLB infects trees slowly and in erratic patches. But it’s possible that the specific leaves sampled were negative for the disease, and the tree was indeed infected.

John Krist, CEO of the farm bureau in Ventura County, says these “four-legged pest control advisors” were trained in Florida through a USDA grant and help the county detect HLB early.

Since 2019, Krist says, of the thousands of trees the dogs have sniffed, they’ve only detected the bacterium in “7 to 8 percent.” The presence of bacterium doesn’t necessarily mean they have the disease, and not all the trees have been tested. But Krist says: “Odds are extremely high that HLB is here.”

Neil McRoberts, a professor of plant pathology at UC Davis, says that California’s climate may impede the psyllids’ ability to spread the disease. “Winters are colder than they like. Summers are hotter and drier than they’re used to,” he explains. But that climate is changing. Temperatures are trending hotter in California, and that could mean increased pest populations, and an increased reliance on pesticides.

When asked about the threat psyllids and HLB pose to California citrus, a spokesperson for the California Department of Food and Agriculture wrote in a statement: “It has been an urgent issue in California for 13 years and has remained a high priority for CDFA.”

Awaiting a Decision

In addition to negative responses to the proposed reduction of neonic use in California, CDPR has received hundreds of letters advocating for an outright ban. “Science does not support pollinator protection based on ‘safe’ exposure levels to systemic insecticides,” reads one line in a 55-page letter submitted by the organization Beyond Pesticides.

Syngenta, a manufacturer of neonic products, disagrees. In a letter to CDPR, the company states that applications of various neonic products when plants are not in bloom could be used without harm to bees. Meanwhile, a letter from Bayer’s crop science division questioned how CDPR interpreted the data.

Even the USDA’s Office of Pest Management, which usually doesn’t weigh in on state level regulations, submitted a letter expressing concern that limiting neonics would hit California’s citrus and grape industries especially hard.

“I think it’s an inescapable conflict that has to be resolved,” says McRoberts with UC Davis. “There are valid arguments on both sides and that’s what makes it such a tricky policy for the state legislature to decide and CDPR to rule on.”

Leading up to the decision, trade group California Citrus Mutual and the grower-funded Citrus Research Board, hired scientific consultants to meet with CDPR and review its methodology. Casey Creamer, president and CEO of California Citrus Mutual, says he’s “optimistic” that CDPR will ultimately decide to ease up on the limits being proposed.

Jen Sass with NRDC says all eyes will be on California this fall when the state decides whether it will rein in neonic use in agriculture. “California is such a big ag state and their ag is so diverse and their climate is so diverse. It’s such an amazing testing ground,” she says. “If California can do it, anyone can.”

Anne Marshall-Chalmers is an investigative journalist at The War Horse and a former staff reporter with Civil Eats. A California native, she spent several years working as a reporter, writer, and audio producer in Tennessee and Kentucky before returning to the Bay Area to earn a master’s degree from the U.C. Berkeley Graduate School of Journalism. Her work has appeared in the Los Angeles Times, Atlas Obscura, USA Today, Bay Nature, Earth Island Journal, NPR, CalMatters, Inside Climate News, and Louisville Magazine. She reports on climate change, agriculture, public health, and the spaces where these topics intersect. Read more >

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