San Diego. - Plants as well as people thrive in the temperate conditions of Southern California. The sunny skies and warm weather attract their share of undesirables too. One of the most recent, and threatening, new residents is Puccinia hemerocallidis, commonly known as Daylily Rust.

The daylily is among the most popular of landscape plants. So when Daylily Rust appeared on plants in Southern California in March 2001, the San Diego County Agriculture department attempted to stem the spread. Unfortunately, by December 2001, a total of four nurseries were infected. Miramar Wholesale Nurseries was hit the hardest. The San Diego site grows the largest selection of daylilies in San Diego County, supplying landscapers and nurseries throughout the state and the nation with thousands of daylilies each year. Nearly 80% of the nursery~Rs daylilies were infected beginning December 2001.

Daylily Rust is a fungus that infects daylilies. Its native range includes Japan, eastern Siberia, eastern China, the Korean peninsula, and Taiwan, but the disease was introduced to the United States from a broker in Central America. It was recognized in the United States in August of 2000 at a nursery in Dearing, GA. Since then, the fungus has spread, infecting daylilies throughout the country.

"Most of the infections have occurred in the South East area of the country," said Pat Nolan, a plant pathologist with the San Diego County Agriculture department. "But it is spreading, and moving quickly."

With more then 1,500 nurseries in San Diego County, identifying those that grow daylilies has been difficult. "If nurseries that grow the plants will call us, we can inspect plants for them," said Ted Matsumoto, the County Agriculture department supervising inspector. For now, County inspectors inspect where possible and bring any suspicious-looking plants back to Nolan for determination. "It's tedious but necessary process."

The fungus is easily recognizable; however, some plants show little infection, while others are covered. One to two weeks after the plant becomes infected, powdery orange spores rise from the leaf. The pustules, which emit these spores, are surrounded by chlorotic tissue that quickly becomes necrotic in more susceptible varieties. Because of the short reproductive cycle of the rust, a plant can be reinfected several times in a single growing season. If left untreated, the plant will become completely yellow and all aboveground tissue will die.

The spores are primarily spread by the wind; they can also transmit between plants that are in close proximity to one another. The spores can also be carried on shoes or clothing.

"At this point we don't know what may exacerbate the problem," Matsumoto said. "Some of the plants are dormant over winter, so determining if they are fungus-free is difficult and time consuming."

At Miramar Wholesale Nurseries (MWN), approximately 80% of daylilies, including 1 gallon, 5 gallon, and field grown plants, were found to be infected. As with other nurseries, the degree of infection at MWN varied by variety. In some cases severe necrosis was discovered, and in other cases, only minute traces of the spores were found.

Of the varieties grown at MWN, Orange King, Stella d'Oro, Lemon Yellow, and Russian Rhapsody were the most highly susceptible. Those least susceptible included Lightning Bolt, Lightning Berry, and Butterscotch Ruffles.

MWN first noticed the problem in early December 2001 when several varieties turned yellow and began to die back.The disease spread rapidly to other varieties, and within a week, traces of the rust were found in nearly all beds of daylilies in the nursery. For two months production and shipment stopped as the company dealt with the problem.

"We entered into a compliance agreement with the San Diego Department of Agriculture to help prevent the spread of Puccinia hemerocallidis," said Joshua Dake, operations manager for MWN. The treatment process was simple but thorough :

1. All plants were quarantined and kept in designated areas.
2. All affected foliage was removed, double bagged, taken to the County Landfill, and buried under the supervision of a County Inspector.
3. Three systemic chemicals are approved for use under the compliance agreement; Propaconizole (Banner Maxx), Azoxystrobin (Heritage), Myclobutanil (Systhane). MWN chose to use Banner Maxx because more frequent applications can be made.
4. If, upon reinspection, the formerly infected plants have grown a symptomless canopy of 6'-10', they become eligible for movement or sales.

"The treatment program has been extremely successful," Dake said. "All traces of rust have been eradicated in approximately 98% of the plants that were previously infected and the other 2% are continuing to be monitored and treated."

Nearly all of MWN's daylilies were released for sale by the end of February 2002, and the remaining plants are expected to be released once they have achieved the suitable height and are symptom free.

Vigilance and compliance with quarantine procedures are required as complete eradication could take several years. The quarantine at MWN did severely affected production of the daylily line. All shifting stock was put on hold, and production stopped for nearly 2 months at the San Diego location. Because the daylily is among the most popular of landscape plants, if untreated, the rust could rapidly spread to uncontrollable levels and do major damage to landscapes nationwide. To contact an inspector in San Diego County, call 1-760-752-4700.

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Sidebar - Daylily

Anyone looking for a low-maintenance yet attractive addition to their landscape should consider a perennial sometimes referred to as the perfect perennial ... the daylily (Hemerocallis hybrid). This is an appropriate reference, as these plants are easy to grow, make an impressive showing, and live practically forever with almost no care. There are few plants that are as tough, persistent, and pest-free. And they are even edible!

Daylilies are herbaceous perennials that bloom from May to September in Southern California. Each bloom is only open for one day, thus the name daylily. However, daylilies are prolific bloomers and compensate with flower buds that open on successive days, providing masses of color. They are highly valued for both their aesthetic and practical qualities.

The durability and low-maintenance characteristics of daylilies make them particularly desirable for commercial landscaping projects. Their ground-holding qualities make them a great choice as a groundcover in sunny areas where the soil is washing away or on a slope that is too hard to mow. They~Rre particularly beautiful as a mass display in flower beds, but make a nice perimeter plant or monument planting.

Daylilies may either stand alone, or can be combined with evergreens, flowering shrubs and annuals to create a colorful, low-maintenance display. It~Rs best to choose companion plants that have a long period of bloom as well as large masses of foliage that are attractive even when there are no blossoms.

Low-growing evergreens such as boxwood, liriope, star jasmine and juniper combine well with daylilies because they provide greenery during the months of the year when the daylilies are semi-dormant or out of bloom. Dwarf flowering shrubs such as Pittosporum Wheeler~Rs Dwarf, Raphiolepsis pinkie, Nandina compacta and Pittosporum crassifolium Nana also make good companion plants because they require little maintenance.

MWN offers daylilies in a variety of shapes and sizes and a rainbow of colors, featuring more than 20 eye-catching varieties in everything from deep rose to bold red to creamy yellow. Some varieties even offer multi-colored flowers. Heights range from dwarfs growing to 11 inches tall to hybrids reaching three feet or more.

Blooms start at less than three inches in diameter and broaden to eight inches or more. Some blooms have long narrow petals and sepals that often curl and twist, others boast wide ruffled petals, and still others feature double flowers, for extra color and impact. The petals themselves might also feature many colors, with contrasting petal and eyezone colors, watermarks, varying petal edges, and much more.