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adult Psyllid
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LERPS
on Eucalyptus leaves
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What do Redgum Lerp
Psyllids look like?
The adult insects are small
(1/8 inch long), slender and pale-green. They are sucking
insects, can jump and fly, and are hard to see. Adults
and larvae feed primarily on Redgum Eucalyptus trees.
Mostly, what is seen are the sugar-like 1/8 inch wide
white cones called "lerps." Larvae are found beneath
these lerps or bumps they have built.
What damage do they
do?
Both adults and especially
larvae suck sap from the leaves and stems thus weakening
Redgums. RLP produces large amounts of sticky clear
liquid called honeydew which stains the ground beneath
trees. A blackish sooty mold grows on the honeydew-covered
surfaces. The lerps and honeydew stick to shoes and
dirty cars, buildings and sidewalks. Heavy infestations
are even more harmful causing leaf drop and severely
stressing trees.
Why arethey a problem?
RLP occurs in Australia where
it is not a problem because it most likely has natural
enemies (small parasitic wasps) that normally keep them
under control. RLP was introduced into California before
1998 without these natural enemies. RLP has become abundant
in California because its favored host plants, certain
species of eucalyptus trees, are commonly grown over
much of California.
Can RLP be controlled?
Biological control for RLP
offers the best hope for controlling this pest. On Wednesday,
June 7, Dr. Donald Dahlsten, Center for Biological Control,
University of California, Berkeley began an RLP biological
control program by releasing a species of small parasitic
wasp in Valley Village area of Los Angeles. This will
be followed by field releases on a weekly basis at other
monitoring sites in the county. We hope that the wasp,
which is barely visible to the naked eye, will provide
long-term control by feeding on larvae of RLP. In September
1999, Dr. Dahlsten brought back the small wasps from
Australia, RLP's native home. Before releasing the wasps
he first ensured that the wasp feeds only on RLP.
The parasitic wasp has been reared with amazing
success in the quarantine facilities at Berkeley and
it is hoped that they will thrive in California. It
was also necessary to get background data on the numbers
of RLP at the release sites so that Dahlsten and his
team could have reasonable certainty that the parasites
would be doing their job.
Once the parasites are released and if they become
established, Dahlsten hopes that the parasitic wasp
will gradually spread throughout the Los Angeles basin.
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