Lettuce Growers Hope Weeding, Research Can Counter Devastating Plant Virus

Population explosion of insect vector contributed to $100 million in losses in 2020

By Mike Hsu. UCANR Senior Public Information Representative

While most Californians are wholeheartedly embracing the moist begin to winter, one group is welcoming the rain extra warily (and wearily) – lettuce growers within the Salinas Valley.

“It’s a blessing, yes, we need the water,” stated Tony Alameda, managing associate of Topflavor Farms, which grows quite a lot of produce in Monterey and San Benito counties. “But, oh gosh: with that water, here come the weeds, here comes the habitat, here comes all the other problems that go along with it.”

Weeds are overwintering havens for a tiny insect referred to as the Western flower thrips, which in flip carries the impatiens necrotic spot virus (INSV) – a plant virus that induced $100 million in misplaced gross income for Salinas Valley growers in 2020.

The agricultural group referred to as it “the biggest problem we’ve seen in a long, long time,” stated Mary Zischke, facilitator of a job power convened by the Grower-Shipper Association to deal with INSV and a associated affliction, Pythium wilt.

Widespread crop failure in 2020

Since INSV was first noticed within the state in 2006, the virus – which poses no risk to individuals – triggered important crop losses in 2019, main as much as a catastrophic 2020. As Alameda’s lettuces started to point out the telltale “bronzing” of the leaves, efforts to bag up or take away the contaminated crops had no impact on the virus’ implacable unfold.

“Nothing seemed to work,” he recalled, “and you just watch those fields collapse, week after week, until you’re just like, ‘Ugh, there’s nothing here to even harvest.’”

After “100% crop failure” that yr in his prime fields on the coronary heart of the Salinas Valley, Alameda tried to dodge the virus in 2021 – shifting lettuce plantings to San Benito County and as an alternative utilizing his most dear land for unaffected crops reminiscent of cilantro, leeks and radishes. By decamping to San Benito, Alameda was in a position to harvest 70% of his standard lettuce yield.

Generally, growers loved a reprieve from virus pressures in 2021. Even on this “good” yr, nonetheless, about one-third of all lettuce plantings within the Salinas Valley had not less than a low stage of an infection, in response to Zischke.

“Since we were attributing a lot of our so-called good fortune – on having less damage this year – to the cooler weather, we know we can’t count on that to get us out of this problem,” Zischke stated. “All the models point to the fact that we’re in a warming climate, so we were fortunate this year.”

More analysis wanted on thrips

Heat waves had been a significant driver of the INSV catastrophe of 2020. Although researchers have established a hyperlink between hotter temperatures and inhabitants will increase of thrips, science nonetheless has loads to find out about these illness vectors.

“Thrips are something we’re trying to understand as much as we can, but it’s pretty tough because they’re a little mysterious in the way they get around and where they overwinter,” stated Richard Smith, a University of California Cooperative vegetable crops and weed science farm advisor for the Central Coast area.

Smith – together with U.S. Department of Agriculture analysis entomologist Daniel Hasegawa and California State University-Monterey Bay plant pathologist JP Dundore-Arias – supplied an INSV replace throughout an Assembly agriculture committee listening to in December.

Recent research have recognized a number of weeds as key “reservoirs” of thrips, together with malva, marestail, and bushy fleabane. The ubiquitous mustards, happily, look like poor hosts for thrips, though their pollen function potential meals sources.

Controlling these weeds – that are starting to spring up as the times lengthen – is a high precedence in the course of the winter months, in response to Smith. Aggressive weed administration within the previous winter was an necessary think about limiting the virus’ unfold in 2021.

And as a result of weeds acknowledge no boundaries, consultants are additionally urging managers of non-agricultural lands to maintain their properties as clear as attainable, together with industrial websites, gear yards and the perimeters of roadways – particularly U.S. Route 101, which runs via the middle of the valley. Some growers have been volunteering to weed their neighbors’ vineyards.

“We’re encouraging everybody – as best they can – to knock down known weed hosts; that’s really critical,” Zischke stated.

Search for long-term options

Within the grower group, there’s “nervous optimism” for the approaching yr, stated Alameda, as he continues to hope for an innovation that might support within the battle towards INSV – whether or not a extra focused pesticide utility or a helpful insect that might deter the thrips.

However, each Alameda and Zischke pointed to the breeding of extra resistant lettuce varieties as the last word answer to INSV – albeit one that’s years away.

“We have a lot of different types of lettuce that we grow, so to move resistance into all the different types of lettuce we grow throughout the season … that’s going to take time,” Zischke defined.

Research funding from the state and USDA – in addition to tasks supported by the California Leafy Greens Research Program – will help expedite that course of. But, for Alameda, the INSV disaster underscores the necessity for extra assets and farm advisors reminiscent of Smith, who has spent greater than three many years cultivating relationships and constructing belief inside Salinas Valley communities.

Alameda wish to see a renewed give attention to bringing “bright, young, passionate people who live and breathe this stuff” to the area, so growers are higher geared up to deal with the inevitable subsequent calamity.

“Hopefully this is a wakeup call to all,” he stated. “This is a valued industry – you have to take care of it; it cannot be taken for granted. The ‘salad bowl of the world’ cannot rest on its laurels.”



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