As many eucs around Canberra at the moment have many lerps, I was wondering
about the extent to which that phenomenon might be affecting the occurrence
of birds here, the matter of lerps having been mentioned already in the same
breath as, for example, Regent Honeyeaters, Swift Parrots and Superb
Parrots. A little lerp-Googling has produced the following information:
(1) Those who raise the quibble that the 'lerp' is the waxy scale and not
the sap-eating insect (a 'psyllid') are correct. Moreover, only some
psyllids create lerps.
(2) The term 'lerp' comes from an aboriginal word, and the same term,
confusingly and presumably with a different derivation, also has something
to do with computers, suggesting a byway into which I think we should all
agree not to stray.
(3) Lerps are formed from the honeydew produced by the nymph stage of the
psyllid. They vary in size and shape according to the species. The
life-cycle could take 1-2 months; a nymph usually makes only one lerp but
could make more than one if it moves to a new site.
(5) There are different theories about lerp outbreaks. One is that drought
stress creates better conditions for psyllid breeding. Another is that the
absence of natural controls is a contributor.
(6) Psyllids rarely cause death of trees, but might contribute to dieback
or death in some conditions.
(7) The 'yellowbox lerp' (the CSIRO uses 'lerp' for the insect, so there
you go, as Mark Latham was fond of saying) is Lasiopsylla rotundipennis,
which feeds on a 'wide range of eucalypts'. Other species (as well?) like
Blakely's Red Gum.
(8) Damon Oliver has written a research paper on the importance of lerps in
the diet of Regent Honeyeaters - in the Armidale area.
(9) Of particular note: like Canberra, California is experiencing a severe
lerp psyllid infestation, on its 'red gum eucalyptus trees' in particular.
Apparently the honeydew is not merely forming lerps but 'drops to the ground
on cars and sidewalks'. (It appears that the LP in question, Glycaspis
brimblecombei, 'excretes much honeydew'.) A control program is in effect,
which includes 'introducing parasitoid natural enemies'. 'Parasitoids', a
curious word, refers to the enemies, not the psyllids. (The parasitoids, to
get our Australian psyllids off our Australian gum trees, are being produced
in 'insectaries' of, respectively, the University of California and the
California Department of Food and Agriculture, the Department of Homeland
Security not being engaged as yet.) It may be of interest that several bird
species, including the chestnut-backed chickadee and the bushtit, have been
observed feeding on infested trees. Regent Honeyeaters and Swift Parrots
are not mentioned in this connection, or at all. One can only hope that, if
a new-generation parasitoid natural enemy finds its way to Australia, the
means will be available to develop a - what would one call it? - a
counter-parasitoid (etc) to safeguard the more ecologically-relevant
psyllids here.
(10) Lerp pictures are available, but their inclusion has been resisted (by
me).
Geoffrey Dabb
email :
ph/fax : 02 6295 3449
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