Briefly in the news

If you notice your eucalyptus trees losing leaves and looking a little

thin, it’s not your gardening skills and you’re not alone.

Some 3,380 red gum eucalyptus trees in Huntington Beach -- 1,500 in

Central Park alone -- are infested with a 3-millimeter-long insect that

sucks the life right out of the tree.

The city has removed 100 trees since the a pest called the Red Gum

Lerp Psyllid was first found in the county in 1998. There are currently

100 more trees slated for possible removal, said John Van Oeffelen,

operations manager for the Huntington Beach public works department.

The small flying insect, native to Australia was discovered in Los

Angeles in 1998 and soon spread to Huntington Beach.

The insect sucks the sugar out of a tree’s leaves and lays eggs on

those leaves. The young insects, called nymphs produce a sticky waxy

shell, or a lerp, for protection.

The lerps appear as white spots on the leaves and cause the leaves to

dry up and eventually die.

The trees can survive these defoliations, but there’s a point when

they can’t keep up with insect’s pace.

Leaves provide an essential function to the trees. Without them a tree

cannot pull water up into itself or make sugar and so parts start dying.

“It creates a mass-energy problem,” said Stephen Holcomb, a consultant

to the city on the project. “A tree needs all its leaves to keep its mass

healthy. As the energy is reduced, a tree’s health is reduced. Some trees

can survive 20 to 30 defoliations, but eventually they will run out of

gas.”

Donald Dahlsten, a leading researcher on the psyllid from UC Berkeley,

is currently studying a predatory wasp native to Australia called the

Psyllaephagus Parasitic Wasp, that might offer a means of control. He

expects data to be available by the spring.

The wasp was released to 26 locations throughout California in June of

2000 and has established populations in 11 of those locations.

“We don’t know yet what the [wasp’s] impact is on psyllid populations

[in California],” Dahlsten said.

Although these wasps have been released in Huntington Beach’s Central

Park none have established any permanent populations.The wasp is the only

natural enemy of the psyllid to be released.

The wasp punctures the lerp and lays its eggs inside. The wasp larvae

hatch and eat their way out of the shell, killing the psyllid.

“It’s best if we can build a significant predator wasp population to

control the insect long-term and let the natural cycle take over,”

Holcomb said. “We’re looking at long-term sustainability, not a

short-term quick fix. Until we develop a biological equilibrium, we’ll

never be able to control it.”

Holcomb and Van Oeffelen discouraged the use of pesticides as an

effective control saying that pesticides must be sprayed frequently to

have any effect and insects often develop resistance to some pesticides.

Part of the problem, Van Oeffelen speculated, is that the city planted

too many of the red gum eucalyptus trees and not enough other species of

trees.

“The problem in California is that we brought the [eucalyptus trees]

with no diseases or insects. Then one [psyllid] came from Australia that

could infect and we didn’t have any controls for it,” Van Oeffelen said.