Growers across commodities in California have been struggling with severe infestations lately. While many factors are at play, they are finding an underlying trend of pests thriving in a warming California.

It has been an “absolutely extraordinary” year for fruit fly activity, according to Andrew Cline, a CDFA entomologist. The population was double the average size last year and this year had a sixfold increase above normal.

“We're in really record-breaking, precedent-setting times,” Cline told the State Board of Food and Agriculture on Tuesday, adding that he was unsure if the flies are coming into California through ecommerce, smuggling, trade or other means.

A single smuggling incident last year in San Jose brought 179 new types of fruit flies that officials had never seen before. It takes a team of CDFA specialists to respond to an incident like this and each layer of response—identification, treatment, quarantine—involves more resources and staff time. With aggressive oriental fruit flies now in 15 counties, those resources are stretched thin, according to Cline.

The various fruit flies making inroads across California feed on hundreds of different plants, posing a threat to farmers across commodities.

“You name it—we grow it, they love it. They see green everywhere,” said Cline. “They're going to come after all of those nice fresh fruits and vegetables that we grow across the state either commercially or residentially. These are things that are going to hit everybody everywhere.”

CDFA is also charged with protecting the environment from invasive pests. The fruit flies have the capacity to change ecosystem functions—in a state that prides itself as a biodiversity hotspot.

Officials have set around 100,000 traps for the exotic fruit flies, “certainly more than double any other state,” explained Josh Kress, a CDFA program manager. The goal is to find the flies before they infest one square mile, the threshold before prevention becomes nearly impossible. Such a heightened level of regulatory activities is not sustainable for long, which is why the department works closely with USDA on quarantines, he said.

Board President Don Cameron hopes to boost those resources with a funding request to Governor Gavin Newsom. CDFA Secretary Karen Ross cautioned the budget outlook for the next fiscal year remains murky amid a mild recession and turned the attention to USDA Secretary Tom Vilsack and Jenny Lester Moffitt, the agency’s undersecretary for marketing and regulatory programs.

Lauren FannLauren Fann, Almond Board

But the fruit fly invasion is not the only battle experts are waging with invasive pests.

Almond farmers are grappling with higher levels of navel orangeworm due to several factors, according to Lauren Fann, a pest management specialist at the Almond Board of California.

A series of atmospheric rivers at the start of the year prevented growers from getting into the orchards to shake out the mummy fruits that host the insect. Poor weather during bloom led to fewer nuts, which grew larger and tend to crack and split, exposing the nuts to the orangeworm. At the same time, almond prices are low, making sanitation and sprays expensive for treating the trees. More host plants are available due to an uptick in abandoned orchards—with some growers cutting their investment and walking away while others sit and wait while crews work through a severe backlog for removing and chipping old trees.

Central Coast lettuce growers, meanwhile, have been in crisis response since 2020 over an outbreak of Impatiens Necrotic Spot Virus (INSV) and the resulting Pythium wilt.

“People were writing the obituary of the lettuce industry in Monterey County about this time last year,” said Mary Zischke, who leads a task force on the issue at the Grower-Shipper Association of Central California.

It’s now apparent that heat waves have a role in the spread of INSV. Average temperatures were above normal in 2020 and the industry was hit with $100 million in losses. After a cool break, a warm 2022 brought $150 million in losses. The top weeds found across California are good hosts for the western flower thrips, which transmit the virus, and farms that bud up against dairies with weeds have been vulnerable, according to Zischke.

She noted a significant impact of climate change, with fewer and shorter periods for temperatures to drop below the level needed for thrips development. Dry winters, meanwhile, mean less mortality during the off season and heat waves put stress on the cool season vegetable, resulting in more wilt damage.

The population this year has been mild, Zischke believes, because delayed planting due to wet or flooded fields created a longer period without the thrips’ best host, lettuce. A better water supply also led to more fall plantings in the Central Valley, giving the Salinas Valley a break.

Yet the cool year and late rains have been an impediment to vineyard managers, who have fended off mildew, rot and fungal pathogens. Like the almond industry, abandoned vineyards are providing safe harbor for pests like the glassy winged sharpshooter, according to Aaron Lange, who leads vineyard operations at Lange Twins Family Winery and Vineyards.

After the Air Resources Board banned open agricultural burning in 2021, the waitlist has grown “very, very long” for removing and treating vineyards and Lange fears the industry will soon hit a wall.

About 20,000 acres need to come out of production to balance the industry’s supply and demand curve, with most of that correction occurring in the Lodi region.

Farm costs here have shot up 250% since 1997 while the price for cabernet sauvignon has dropped. Lange is aware of many farmers going into the crop year not knowing if they will have a contract for their grapes, forcing them to perform just minimal farming and pest prevention.

And the list of threats continues to grow.

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While the industry was shifting focus to combatting the glassy winged sharpshooter about 20 years ago, a traveler from Israel came to California with a suitcase of grapevines infested with the vine mealy bug. The tiny insect is small enough to blow in the wind and caught vineyard managers off guard. The virus it spreads can kill a vineyard within a few years and the bug is nearly impossible to eradicate, explained Lange. Farmers have planted new vineyards at $45,000 per acre only to see them wiped out from an infestation carried over from their neighbor’s vineyard.

With few pesticide tools left to combat such pests, Lange and his colleagues have been experimenting with alternative practices, including a herd of 900 sheep on his vineyard.

Tomato growers, meanwhile, have been battling a pest since World War II, though changes to climate and cropping patterns are posing new problems, according to Mike Montna, president and CEO of the California Tomato Growers Association. The beet leafhopper, which spreads beet curly top virus, now lives on the Central Valley floor year-round and is moving north, with new damage documented in Sacramento Valley counties.

A new parasitic weed is also preying on tomatoes in Yolo County. Broomrape can lay dormant in the soil for decades until a host arrives and each plant can spread about 10,000 seeds, explained Montna. The only known way to kill it is methyl bromide, a fumigant California banned in 2005. Broomrape can lower yields by 70%.

Secretary Ross has been alarmed by how often CDFA is finding a new disease or more pests in California’s agriculture fields. As CDFA crafts a “master plan,” dubbed its Ag Vision, Ross is seeking ways to focus the department’s limited resources across more commodities. Montna suggested a task force to seek out new tools to use on multiple crops, while Lange hoped for better engagement to help neighboring farmers work together and Zischke pushed for streamlining regulatory hurdles with bring new technologies to market. Ross is also considering grant opportunities for research to support new practices under the umbrella of the Department of Pesticide Regulation’s sustainable pest management initiative.

While Ross said the discussion on pest issues was informative, she also found it uncomfortably scary.

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