In general, Psyllidae are similar to aphids
while others look like the miniature of cicadas, but with
much longer antennae. Psyllids have strong jumping legs
with enlarged femora. Lerps spin conical scales (lerps)
to shelter underneath. The nymphs may produce white waxy
secretions or honeydew. Most species have to be
considered as pests of agriculture because they feed on
plant juices. Some transmit viral diseases or produce
galls. However, some are suitable as biocontrol agents if
their host is a weed. Heteropsylla spinulosa for
instance is used for the control of the giant sensitive
plant Mimosa invisa in PNG. Of importance for
several species of Eucalyptus are the Lace and
Basket Lerps Cardiaspina spp.
and Glycaspis spp. (Psyllidae).
Lerps are scales or tests of most immature stages. The
nymphs live and feed beneath the lerp and are protected
there from desiccation. In the case of Cardiaspina the
lerps resemble lace or a turned-over basket, whereas the
lerps of Glycaspis are of white, fibrous material.
The shape of the lerp is characteristic for the species
and can be used for their diagnostics. The lerps are made
from starch, derived from the plant sap. While sucking
the plant juice, the nymphs inject enzymes that break
down the plant tissue. This later becomes visible as
brown, red or yellow discoloration of a leaf. The feeding
puncture usually looks irregular and scar-like. The
adults looking like the miniatures of cicadas, are
without lerps and hardly exceed 5 mm body length. Most
species are of brown or yellowish coloration and are good
fliers due to their well developed membranous wings.
Because of their jumping hindlegs they are also called
jumping aphids. The females possess a
saw-like ovipositor which helps insert the base of the
eggs into the leaf to avoid desiccation. A female can lay
several hundred eggs during her short life-time. There
are five or more generations per year in the Tropics.
Psyllids cause a more or less severe defoliation of
their respective host. Some species cause the necrosis of
a leaf, others only its discoloration. Natural enemies
are spiders, mites, ladybirds, lacewings, parasitic wasps
and some birds. Prolonged psyllid outbreaks result in a
considerable loss of increment and die-back of the host.
Severe outbreaks were not have not been reported in PNG
so far.
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Cardiaspina spp. lerps on Eucalyptus
leaf

Cardiaspina spp. adults

Glycaspis spp. lerps on Eucalyptus
leaf

white, fibrous Glycaspis spp.
lerps
(reproduced from CSIRO, 1991²)
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