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Photo: Beautiful daylilies like these are a perennial favorite in American gardens. Link to photo information
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Read the magazine story to find out more.

Researchers Identify Daylily Threat

By Amy Spillman
November 6, 2002

Daylilies are one of the most popular perennials grown in the United States. They are pretty, easy to grow and relatively low-maintenance. But something began attacking U.S. and Costa Rican daylilies within the past two years--a fungus that had never before been seen in the Americas. It was first reported in Georgia during the summer of 2000 and has since spread to at least 20 other U.S. states.

For a time, scientists weren't sure what this threat was. They knew it resembled a species of fungus found on daylilies in eastern Asia, but they didn't have enough hard evidence to identify it conclusively. Now, however, researchers with the Agricultural Research Service's Systematic Botany and Mycology Laboratory (SBML) in Beltsville, Md., have proof that the fungus attacking American daylilies is an Asian species.

Puccinia hemerocallidis, the fungal culprit, was first described in Siberia and has also been reported in the Far East. It is a type of rust fungus, a group so named because of the rusty-colored spots, ranging from yellow to orange to dark-brown to black, that form on infected plants.

When scientists in the United States first began working to identify the fungus attacking U.S. and Costa Rican daylilies, they did not have a modern description or illustrations of P. hemerocallidisto to consult. Mycology researchers at SBML, including José Hernández and Lisa Castlebury, as well as Mary Palm, a mycologist for the U.S. Department of Agriculture's Animal and Plant Health Inspection Service stationed at SMBL, have since rectified that situation.

They compared American daylily rust specimens with samples collected in China, Japan, Russia and Taiwan. Their study included both microscopic examination and DNA sequencing. Although variations existed between samples, the researchers found that all of the specimens were of the same species.

Read more about their findings--and who will benefit from them--in the November issue of Agricultural Research magazine.

ARS is the USDA's chief scientific research agency.

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