MADRAS, Ore. — Researchers at Oregon State University have received a $3 million federal grant to study a harmful bacterial disease impacting carrots — one of the Northwest’s signature seed crops sold across the U.S. and around the world.

More than 50% of all hybrid carrot seed is produced in Central Oregon, Central Washington, Southern Idaho and Northern California, according to OSU. The farm gate value of U.S. carrots was $731.5 million in 2018.

But growers say bacterial blight, caused by the pathogen Xanthomonas hortorum, is one of the most significant threats to carrot seed production, jeopardizing both the long-term sustainability and economic vitality of the industry.

Enter Jeremiah Dung, an associate professor and plant pathologist at OSU’s Central Oregon Agricultural Research and Extension Center in Madras, who is leading an 11-person team examining the disease and coming up with new tools for farmers. 

“Hopefully, with this focused effort, we can make some inroads toward better understanding the disease,” Dung said. “The ultimate goal is, if we can better understand the disease, we can develop more focused or enhanced management strategies.”

Dung and his team secured the four-year grant from the National Institute of Food and Agriculture in September. Laboratory work is underway testing whether certain bacteriophage products may be effective at treating blight in carrots. Phages are essentially a virus that infects only bacteria. 

“They’ve been used for other Xanthomonas diseases in peppers and tomato, so we’re investigating it for its use on blight in carrot,” Dung said. 

Based on whether the experiments are successful, Dung said the products may be used in field trials during future years of the project.

Bacterial blight has been an problem for carrot seed producers in the high desert climate of Central Oregon for decades. The bacterium is known for causing lesions on the plants, which in turn reduces photosynthesis and yields.

However, obvious symptoms of the disease do not typically appear unless the bacterium is already present at high levels.

The pathogen is also seed-borne, making it especially pernicious and difficult to contain.

“Everybody wants clean seed, or healthy seed, which is understandable,” Dung said. “The industry spends a lot of money toward trying to manage this bacterium.”

Seed treatment is typically done post-harvest and involves soaking seeds in water heated to 125 degrees Fahrenheit for 25 minutes. But Dung said that method is expensive and not always practical for larger volumes. Plus, it can reduce the quality of the seed, lowering germination rates and hampering marketability.

If researchers can better understand the disease, how it spreads between fields and how it infects seeds to begin with, then Dung said they can potentially come up with better solutions for growers.

“It’s not an easy problem to solve. Bacterial diseases are notoriously difficult to control,” Dung said. “If we can better understand the epidemiology and disease cycle from seed to root, then that should help inform better management strategies in the future.”