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The uncharacteristic wet winter this year in the desert hasn’t been all bad.

Todd Fitchette, Associate Editor

February 28, 2024

2 Min Read
Downy mildew in spinach
Yellowing in these spinach leaves is symptomatic of downy mildew. Jim Correll, a plant pathologist with the University of Arkansas, is studying spinach grown in the desert for varieties that may be resistant or tolerant to plant pathogens.Todd Fitchette

Farmers and plant pathologists tend to have an opposing view of crop diseases. While some can curse the outcome, others see opportunities.

The uncharacteristic wet winter this year in the desert growing region in southwest Arizona hasn’t been all bad, depending on who one talks with. For Jim Correll, a plant pathologist and distinguished professor with the University of Arkansas, the wet winter was opportunistic as he works to understand downy mildew and other plant pathogens in fresh market spinach.

Each winter Correll plants about an acre of spinach at the University of Arizona’s research farm in Yuma. He has similar studies near Salinas each fall. This year’s desert growing region study included 70 different varieties, replicated three times across 210 plots. From it Correll is testing the new releases by various seed companies for their tolerance of or resistance to plant pathogens.

According to the University of California, downy mildews require wet, humid conditions to flourish. Yuma saw that this winter. Airborne spores can land on susceptible plants with water on them, causing an infection that can make the crop unmarketable.

During his work in spinach, Correll has seen commercial spinach breeders produce more varieties to stay ahead of plant diseases and their changing strains. He likens the growing number of disease races – these are strains of the pathogen that hits a different combination of genetics in spinach – to a thoroughbred racehorse. These pathogens can mutate faster than scientists can hold them back.

Related:Plant pathologists in a race against downy mildew

New varieties

“The companies are coming out with a lot of new varieties,” he said. “When I first started spinach years ago, there were maybe five or 10 spinach varieties, now there’s about five or 10 from each company each year, so we get a lot of new combinations of genetics.”

Correll’s work in Arizona and California is critical as the two states produce about 95% of the fresh market spinach in the U.S.

“We’re making progress on what we understand about the pathogen and the genetics,” he said. “We still haven’t solved the puzzle, but we’re certainly making progress.”

Correll was available at the University of Arizona Extension farm in February to talk with growers, plant breeders and other researchers on his work in spinach. He plans to hold a similar event later this year near Salinas to discuss the findings from his studies in that region.

Correll is part of a $3.5 million effort at the University of Arkansas to find solutions to control fungal diseases in spinach.

Related:Drip curbs downy mildew in spinach

About the Author(s)

Todd Fitchette

Associate Editor, Western Farm Press

Todd Fitchette, associate editor with Western Farm Press, spent much of his journalism career covering agriculture in California and the western United States. Aside from reporting about issues related to farm production, environmental regulations and legislative matters, he has extensive experience covering the dairy industry, western water issues and politics. His journalistic experience includes local daily and weekly newspapers, where he was recognized early in his career as an award-winning news photographer.

Fitchette is US Army veteran and a graduate of California State University, Chico. 

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