Topics

Lerp Info...


Robert A. Hamilton <robbham@...>
 

Hi Jim & the rest of SB,

FYI here's a copy of what Kimball Garrett posted to Calbird on 3 Sept.
1999:

-Robb Hamilton

Calbird:
Most of you are aware of the extent to which birds in the coastal
regions of California exploit eucalyptus trees for nectar, particularly
in winter. Searching groves of flowering eucalyptus has become a
requisite modus operandi on Christmas Bird Counts, with the rewards
often being good counts of overwintering hummingbirds, orioles,
tanagers, grosbeaks, and wood-warblers. Given that eucalyptus are
among the dominant trees in many urban and suburban regions of
California, it is hard to imagine birding in the region before
(and after?) the establishment of these exotic trees.

You might have heard of a recent insect pest that is affecting
(and in some cases decimating) eucalyptus trees in southern
California. It is the Red Gum Psyllid, Glycaspis brimblecombei.
The larvae of these psyllids excrete a small conical "lerp" (made of
sticky, sugary "honeydew") that encapsulates the larva. An affected
eucalyptus is easy to spot because of the sticky lerps on the
leaves, a virtual "rain" of sticky honeydew from the tree, and,
ultimately, lots of dead leaves and even complete mortality.
Infestations grow fastest in the warmer months, and are
exacerbated by drought and other stresses. For example,
Elysian Park (near downtown Los Angeles, and so productive
last winter for orioles, tanagers, and warblers) has been
severely impacted, with hundreds of apparently dying
eucalyptus trees. Maintenance agencies will almost
certainly cut down affected trees rather than risk injury
to the public from falling branches, etc. Some eucalyptus
species are more susceptible to this pest than others;
impacted species include Red Gum Eucalyptus, sugar gum, blue
gum, and a few other.

For more information on this pest, see the Los Angeles County
Agricultural Commission's web site: http://acwm.co.la.ca.us

Where it gets interesting is that there are entire guilds of birds
in Australasia which exploit these lerps for food. Such feeding
habits are especially typical of honeyeaters and pardalotes.
I'm not suggesting that we import these birds, but it will be
very interesting to see if our native birds will exploit this
potentially abundant food source. So I urge all of you who bird
in a favorite park or other site with infested eucalyptus trees
to pay attention to this.

Furthermore, should this infestation result in widespread loss of
large numbers of "our" eucalyptus trees, then the ramifications
for overwintering hummingbirds, orioles, tanagers, and wood-warblers
are potentially severe (though one might view this as more of a
"readjustment" to pre-European conditions). These things are
hard to monitor, so birders this winter should pay close attention
to bird numbers in affected areas.

G'day,

Kimball Garrett