Oleanders Wilting Away From Blight

When it came time to landscape the Tustin Market Place shopping center, there was hardly any hesitation. There would have to be oleander shrubs, those lush, evergreen, flower-laden staples of Southern California greenery that line the freeways and withstand the hottest summers and driest droughts.

Soon there was a profusion of flowering oleanders decorating the shopping center.

Now they’re dead and gone, and nearby, roadside oleanders are being ripped out and replaced as well.

The miles-long privacy hedge of oleanders that surrounded the Annenberg estate in Rancho Mirage is gone too--replaced by a stark, concrete wall. And some of the oleanders at the golf course across the road are dead, looking as if they’ve been blasted with a blow torch.

The oleander--a shrub so hardy, trouble-free and drought resistant that it became a mainstay of the Southern California roadside landscape--is being assaulted by a bacterium carried by an insect new to the region. Together, the bug and the bacterium are threatening to make the oleander a memory.

The blight has descended on Orange, San Diego and Riverside counties. It is also reported to be in Los Angeles County, although horticulturists haven’t confirmed any cases.

Both the bug and the bacterium are cousins of the team that caused Anaheim disease, the blight that in the late 1880s wiped out the flourishing wine industry in Los Angeles and Orange counties. That blight, now known as Pierce’s disease, is so persistent that grapevines planted today in the Santa Ana Valley, Westwood and Brentwood would have little chance of survival.

California Department of Transportation officials, who regularly receive fan mail from tourists praising the oleanders along the freeways, are worried. The department has perhaps 100,000 of the shrubs statewide.

Caltrans has hired UC Riverside to find a pesticide that might help. At stake is whether lush greenery on freeway medians will have to be replaced with concrete and steel.

Some researchers believe that there is little chance of successfully fighting the pest. The University of California formed a task force last spring, but a year of study has not prompted any optimism.

“We don’t have any way to combat this disease,” said Alex Purcell, a professor in UC Berkeley’s division of insect biology.

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There is no cure for the bacterial infection, and trying to kill the insects carrying it “just isn’t going to work,” Purcell said. “You can control 99% of the insects and reduce the spread by only 5%,” because remaining bugs would be more than enough to keep the disease spreading. It takes just one bite to infect a plant, he said.

The nursery business is worried too.

The California Assn. of Nurserymen has given $10,000 to UC Riverside to determine whether this new disease is a threat to other plants. So far, only one has been found: periwinkle, or Vinca major, a popular ground cover with dark green leaves and lavender-blue flowers.

The disease, called oleander leaf scorch, has no cure, researchers say. It was first noticed in Palm Springs in the late 1980s but didn’t come to the attention of scientific investigators until 1993.

A year later, it was identified 75 miles away at Tustin Market Place, a shopping complex in the Tustin Ranch area along Interstate 5.

Apparently it arrived in nursery stock. The bacteria multiply so slowly that symptoms do not appear until a year after infection, Purcell said. “This was before anyone knew the disease existed. You can’t really blame anybody.”

The center, built in stages beginning in 1988, “had a ton of oleanders,” said Michael Wilson, the center’s operation manager.

But their leaves, usually a rich green throughout the year despite heat and drought, were turning brown along the edges. They looked as if they were getting no water, and Wilson called his landscaper to complain.

“We were completely in the dark,” said David W. DuBois, president of Mission Landscape Service in Santa Ana. “We’d been maintaining them for four or five years. There was water at the roots, but it wasn’t getting to the plants. They were dying, and normally, you can’t kill these plants if you try.”

Ralph Carhart, senior landscaper for Caltrans, was puzzled as well. Since the 1930s, oleanders have been planted along the state’s roadsides and median strips in the harshest climates, “because you could always count on them,” he said. “They could be burned up or wiped out by a traffic accident and they’d come right back up from the ground.

“About the only place they don’t grow is the Sierras and the North Coast,” he said.

The potential for wide-spread infection is “a nightmare,” Carhart said. As if to bring the point home, the oleanders at Caltrans’ maintenance yard in Orange are dying.

“For all practicality, I can tell you we would not attempt to replace the oleanders in the medians. If there’s a replacement, it will be something engineered.”

Kevin Tong, a Caltrans landscape architect, said maintenance crews have tried severely pruning infected oleanders, but although the foliage grows back seemingly healthy, it’s still infected and doomed. “It might squeeze another year or two out of the plant, that’s all,” he said.

To add insult to Caltrans’ misery, recent tests by Marcy Grebus, a plant pathologist at UC Riverside, indicate that the disease can be spread by unsterile pruning tools, a first for this family of bacteria. (A 10% to 20% solution of household bleach should kill the bacteria, Grebus said.)

UC researchers say they can’t tell how long this bacterium has been in California. It can exist in some plants without causing harm, waiting to be carried to an oleander by some accommodating insect.

They believe that the insect--the glassy-wing sharpshooter leafhopper--arrived sometime in the late 1980s, probably brought into California as eggs in plants. Such infections are supposed to be caught at border checkpoints, but because the eggs are inside plant tissue, they’re easy to miss, Purcell said.

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There had been sharpshooters in California before; one was responsible for the spread of Anaheim disease. But the glassy-wing, a native of the southeastern United States, is new to the state.

The characteristic of bug and bush was a disastrous combination.

One of the oleanders’ virtues was its easy propagation. Merely cut off a branch, plant it in soil, and you have a new oleander. But that created new plants that were genetically identical, generation after generation. If a disease could affect one, it could affect them all, and, in Purcell’s words, “we were planting one every 20 feet all the way to the horizon.”

He said that it’s too soon to predict the long-term effect of the disease.

The American chestnut was a dominant tree species in the eastern United States, but disease drove it to near extinction.

But Dutch elm disease failed to eliminate the elm, “and I think this oleander leaf scorch is going to be closer to that. “It’s going to be very serious and going to eliminate oleanders from certain areas, but where and how far the disease will spread, we can’t tell,” Purcell said.

“At the very least there will be places in Southern California where you don’t want to replant oleanders. Nobody’s planting them in Palm Springs, and I wouldn’t plant one in Tustin for sure.

“At the worst,” he said, “the oleander is going to be a rare plant in California.”