A new plant disease threatens to blemish the reputation of
Georgia day lilies. Timely identification and strict regulatory
efforts, though, have stopped the disease for now.

The disease, day lily rust, was first identified in Georgia in
August 2000, said Jean Woodward, an Extension Service plant
pathologist with the University of Georgia College of
Agricultural and Environmental Sciences. It has also been found
in Florida, Alabama, South Carolina and California.

“Right now, the day lily rust is a concern for nurseries in the
state,” Woodward said. “The average gardener shouldn’t be
worried, but should be aware.”

Apart from their beauty, day lilies have the reputation for being
low-maintenance plants. The rust disease could compromise that
reputation.

Stopping the Spread

“If we let the rust go and don’t stop its spread, 10 or 20 years
from now there may be a lot of day lily rust around,” Woodward
said. “There’s a day lily in every garden and every roadside, and
there’s a chance this could spread.

“But because we were so quick to identify the rust, get the right
people involved and get information out to major growers to watch
the imported day lilies,” she said, “we were able to get on top
of this.”

It has worked. Nurseries that had the rust, she said, aren’t
seeing it this year.

Woodward wants consumers and gardeners to be aware of the new
disease, though. If you believe a day lily may be suspect,
contact the county extension service.

Looks Like Streak, Acts Like
Rust

Initially, the rust looks a lot like another common day lily
condition known as leaf streak, which causes tanned spots on the
plant.

“If it (the day lily) has a sunk-in and water-soaked appearance,”
Woodward said, “(don’t) be concerned. It’s leaf streak.”

If it’s the new disease, though, within two weeks a fungus will
produce powdery spores on the day lily. The bright orange spores
will be on both the upper and lower leaf surfaces, she said.

The disease can spread fast, because the wind easily carries the
spores. “Because it’s rust, it’s not going to kill the plant,”
she said. “The rust needs living tissue to survive.”

The rust’s survival depends greatly on the type of day lily.
Georgia grows two types: dormant and nondormant.

The rust may not survive the winter on dormant varieties,
Woodward says. But it will survive on nondormant types, as well
as on older leaf tissue during milder winters.

“One year a day lily could experience the disease and the next
year be totally free of it,” she said.

Big Domestic Industry

Day lily rust is native to Asia. However, it’s believed to have
been introduced into at least one Georgia nursery from plants
originating in Central America.

Day lilies are commonly shipped into the United States from
Central and South America. Most of the day lilies grown in these
countries, particularly in Central America, originate in the
United States, not in Asia.

The actual origin of the disease, then, is a mystery. Woodward
said it may have come to the United States from Europe. U.S. day
lilies shipped to Central America were then shipped back to U.S.
growers.

“If a grower has rust (in his day lilies), the grower should cut
back the foliage, burn it and get into a fungicide spray
program,” she said.

Day lilies are the No. 1 perennial in the country, she said, and
the Southeast produces most of the day lilies sold in the United
States. Production of day lilies contributes greatly to Georgia’s
$400 million nursery industry.

Georgia is home to four of the top nursery growers in the country
and the largest nursery east of the Mississippi River. “The
industry is growing in Georgia at about 5 percent a year,”
Woodward said.