Advocate • Connect September/October 2019 27
Gardening
CROP-SAFE
Commercial woven anti insect mesh- Helps to prevent damage to crops from insects
such as the potato Psyllid and other small bugs - PP¿QHPHVKVL]H
- 3.7m x 50m rolls, can be fabricated to custom
widths & lengths - High light transmission
- Strong & durable - can be layed directly onto
crops - Long life - UV stabilised
BUG-NET
Lightweight knitted anti insect mesh- Light weight anti-insect mesh.
- 4m x 30m rolls, can be fabricated to
custom widths & lengths - High light transmission, lets air and
water permeate - Strong & durable - can be layed
directly onto crops - Long life - UV stabilised
- Economical
tomatoes and potatoes. Biosecurity staff
concluded that TPP nymphs may have been
accidentally introduced into New Zealand
on chilli peppers smuggled in from the west
coast of the USA.
There are higher concentrations of
TPP in Auckland and in the East Coast
region. The psyllid has slowly moved down
the country and can now be found in
Southland.
It has become a severe pest in many
outdoor and greenhouse crops. It prefers
plants in the solanaceae family – see
sidebar. It’s also found on solanaceous weed
hosts, including black nightshade, African
boxthorn, poroporo and Jerusalem cherry.
Although not a solanaceous plant, kūmara
can also act as a host to psyllids, but they
don’t breed very well on them.
Psyllid life cycle
The TPP breeds all year round, developing
slowly in spring, with the peak period
from late summer to early autumn. In
greenhouses there may be many generations
a year. Around the Auckland region, up to
7–8 generations of psyllids can be produced
a year.
Psyllids have three stages of
development: adult, egg and nymph.
Adults are about three millimetres long,
light yellow when they first emerge, and
darken to brown or green after a few days.
They have pale markings and a white band
on their abdomens. They have wings but
in New Zealand have not been shown to
travel very far. They can be dispersed by
wind and by the movement of infested plant
materials.
The female psyllid can mate more than
once and lay up to 200 eggs over three
weeks, depending on the host plant. Eggs
are yellow and borne on small stalks. They
are commonly seen on the edges of leaves
but can found on all parts of the plant and
stems.
Nymphs emerge from the eggs as flat
scale-like insects, light yellow to tan to
greenish brown in colour. You can see them
reasonably easily. They generally remain
in one place to feed, usually underneath
younger leaves.
Psyllid nymphs go through five stages
of development (instars) and shed their
tough skins (moult) each time to get bigger.
Their cast skins can be seen on leaves next
to newly emerged nymphs. At later stages,
their wing buds begin to develop, so when
the adults finally hatch they can fly straight
away.Feeding
At the adult and nymphal stages, the pests
plunge their syringe-like mouthparts into
the plant to draw up the sap. Plant sap
contains large quantities of water and sugar,
which psyllids don’t need, and very littlePlants that can be
affected by the psyllid- 7RPDWRHVDQGSRWDWRHV
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Above: Zebra chip disease symptoms in a potato: uncooked (left) and fried (right).
Photo: USDA ARS / Joseph Munyanezaprotein, which they do need, to produce
their eggs.
The excess sugar and water are ejected
as a sweet, sticky secretion called honeydew.
Before the insects excrete it, they cleverly
wrap it in small parcels of white wax, called
‘psyllid sugars’. In high infestations, these
pellets can cover leaf surfaces.