Is climate change causing the price of lettuce to skyrocket

In nearly four decades of growing lettuce, spinach, kale, and other leafy greens in California and Arizona, Tony Alameda has seen many bad years. But recently, he said, there have been many more “noticeably bad” years in a row.

“2022 is probably the worst thing we’ve ever seen,” said Alameda, vice president of Top Flavor Farms, a family business he runs with his brothers. In October and November, dual outbreaks of a soil-borne disease and an insect-borne virus devastated the Salinas Valley and wilted thousands of hectares of lettuce crops.

Now, winter growth schedules and changing weather patterns mean pitch has migrated from the Central Coast Valley, which served as the setting for John Steinbeck’s Of Mice and Men and other novels, to the desert-growing regions near the US-Mexico border.

“We’re going from a problem in the north to a problem in the south,” Alameda said. “These are completely separate issues, but they all add up to a really long period of vegetable shortages.”

As a result, consumers across the country could see sharp increases in the price of lettuce, with the cost of a box of iceberg lettuce skyrocketing from about $20 in December last year to over $105 earlier this month, according to US Department of Agriculture data. The Mercury News reported that some vendors were charging nearly $11 for a single head of lettuce.

However, experts say bad luck alone cannot be to blame. The virus Impatiens Necrotic Spot Virus or INSV and the disease Pythium wilt have both been around for years. But the warming brought on by climate change is creating more favorable conditions for thrips, the insect that carries INSV, to thrive.

“In the last probably 10 years, we’ve seen milder winters, which has really allowed the thrips population to thrive around here,” said Jennifer Clarke, executive director of the California Leafy Greens Research Program, which is under the agency of the California Department of Human Resources food and agriculture. Clarke said INSV was first reported in the state salat around 2006, but was never a problem big enough to cross an economic threshold.

“Insects are interesting because they’re really running out of degree days, so with warmer temperatures it speeds up their life cycles, it speeds up their reproduction,” she said. “When you have cooler weather, it kind of slows everything down. So much of our control is up to Mother Nature right now.”

California in particular is being plagued by western flower thrips, according to Daniel Hasegawa, a research entomologist at the USDA’s Agricultural Research Service in Salinas. The tiny, slender beetles measure just 1 or 2 millimeters, so they can be hard to spot and even harder to control, as they can hide in a plant’s folds from the fog of insecticides.

Hasegawa said the thrips transmit INSV through feeding, similar to how mosquitoes can transmit pathogens to humans. Humans don’t get sick from eating INSV-infected lettuce, but the plants do develop brown spots and areas of dead tissue.

“That is the big question, what has changed. This virus already exists, but why has it reached some of the devastating proportions that we have reached this year?” Hasegawa said. Based on available weather and insect surveillance data, “over the past 20 years, with warmer temperatures, it appears that insects’ ability to evolve during winter is much more likely.”

The presence of Pythium will only add to the challenges this year, experts said. The disease is transmitted in soil by fungal-like pathogens that can rot roots and cause infected plants to wilt and collapse. Although many plant varieties are somewhat tolerant of Pythium wilt on their own, INSV can make it worse, Clarke said, “so we often see the two as a common occurrence.”

It was the two together that wiped out Salinas’ crops this fall, said Richard Smith, a researcher with the University of California’s Cooperative Extension Program, which sends agricultural advisors and researchers into local communities. While both have historically presented farmers with challenges, something has changed in recent years to worsen the impact on lettuce growing.

“There were these hot spells that we think triggered the soil-borne disease,” Smith said. He wondered if climate change might be a factor.

“That’s a question we have,” Smith said. “All you can do is conclude that maybe that’s part of the problem. But one thing is true. These hot spells were unprecedented. Is this global warming? Who knows? Could be.”

In September, nearly all of California burned under a record-breaking heatwave that lasted nearly two weeks — the kind of extreme heat events researchers say will become more frequent and intense as the climate warms.

The shaky fall season was just the beginning of the challenge this year. Normally around December the supply of lettuce shifts to the southern desert areas around the Imperial Valley. But the disease problem at Salinas meant there wasn’t enough lettuce to get suppliers through this transition, said Christopher Valadez, president of Grower-Shipper Assn. from Central California.

Additionally, these desert farms have experienced unusually cool weather that is delaying the maturity of the lettuce crop they have. The Imperial Valley area has seen multiple frost warnings in recent weeks and lettuce sometimes gets icy in the mornings.

“Any current shortage of lettuce is a shortage of lettuce produced from the desert production regions such as California’s Imperial Valley and the Yuma, Arizona production region,” Valadez said.

“Going forward, there is one variable that we cannot control, and that variable was temperature,” he said.

Valadez said while he expects the market to stabilize and prices to fall again, that doesn’t solve potential disease and virus problems in the upcoming Salinas farming season, which begins in late February.

Norm Groot, executive director of the Monterey County Farm Bureau, said the organization did not record total crop loss that year, but in 2021, when there was a similar problem of excessive heat linked to pests and diseases, there was a loss of 100 million dollars.

“There will probably be more this year,” Groot said. “Unless we can find biological or chemical control for either the insect or the disease itself, we will continue to see these problems in our region. At the moment we have absolutely no control over this disease.”

The fertile Salinas Valley runs almost the entire length of Monterey County and is separated from the larger Central Valley by a mountain range. The lettuce crop here is estimated at $1.2 billion and accounts for a quarter of Monterey County’s agricultural value, Smith said. If the problem persists and growers choose to leave the area to plant lettuce, “it would be a disaster for this community, for the workers, and for the retailers.”

Smith said experts are working to find a solution to the bottlenecks. So far, researchers and seed breeders have found that there are lettuce varieties that show some disease resistance, he said.

“This looks promising,” he said, although he noted it doesn’t solve the problem of other illnesses or excessive heat. “We approach it from every conceivable angle.”

Alameda, the farmer in Salinas, called this year’s confluence of problems “a perfectly bad storm” and said it could take some time for prices to level out at the consumer level. He also feared that another challenge posed by climate change – drought – could soon affect his ability to farm. California and Arizona both rely heavily on water from the Colorado River, which is shrinking to such dangerous lows that officials could soon cut supplies.

“That’s coming up in the very near future – if we have to make a choice when I only have this many gallons of water, what’s the best way to maximize the economic opportunity with that water,” he said. “It’s unrelated to what we’re currently dealing with, but it’s looming very close, very close if the rain doesn’t come back.”

Still, he remained optimistic that genetic improvements, including new disease-resistant lettuce varieties, will help farmers overcome current challenges.

“Salinas is the salad bowl of the world,” he said. “I think we will continue to solve the problems, as we have done with other diseases in the past, to manage to overcome them and continue to thrive. I am 98% sure that will happen. But there’s 2% of me who say keep your eyes wide open.” Is climate change causing the price of lettuce to skyrocket

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