vegetables

22
Ask the industry
Two-spotted mite. Photo courtesy of
Clemson University – USDA Cooperative
Extension Slide Series, Bugwood.org.
with Scott Mathew
R&D
Farm Productivity,
Resource Use
& Management
Recently, I’ve been getting
a few phone calls about
a number of insects that are
causing more issues than
normal, particularly in some
of the areas surrounded by
broadacre farms. I believe this is
due to some early summer rain
causing a flush of weed growth,
promoting the build-up of insect
populations. These weeds have
then been sprayed by farmers
over the summer period,
encouraging insects to migrate
to the only green food source
around – irrigated horticultural
crops.
A couple of insects that have
been particularly busy are
Potato moths and mites.
Potato moths
Potato moths, also known as
Tuber moths (Phthorimaea
operculella), are one of the
most damaging potato pests in
Australia. High count numbers
have been reported in some
of the South Australian potato
growing regions over the last
few weeks. Potato moth larvae
POTATO MOTHS AND TWO-SPOTTED MITES HAVE BEEN
PARTICULARLY TROUBLESOME IN RECENT MONTHS. SYNGENTA
TECHNICAL SERVICES LEAD SCOTT MATHEW EXPLAINS HOW TO
RECOGNISE THESE PESTS AND HOW TO MANAGE THEM.
mine in foliage, stems and the
tubers of potatoes. They are
particularly damaging during
periods of warm, dry weather.
The adult moth is identified by
its narrow, silver-grey body and
greyish-brown wings (wingspan
12-16mm) that are patterned
with small, dark specks. The
moths are mainly active at
dusk but can be seen flying
sporadically in the potato crop
during the day.
The Potato moth lays oval
eggs on the underside of potato
leaves and on any exposed
tubers. When first laid, the eggs
are pearly white; changing to
yellow on maturity and to black
just before hatching. After
hatching, the larvae continue
to grow to an adult size of
15-20mm. The complete life
cycle takes between four to five
weeks. If left untreated, the
larvae cause extensive damage
to both foliage and tubers.
In order to minimise damage
from Potato moth close to
harvest, you should carefully
monitor pest numbers. If
detected, decide on the
appropriate control measure.
It is often beneficial to apply
an insecticide just before the
potatoes are desiccated to
prevent the insect larvae from
entering the soil and moving
down to damage the tubers.
Two-spotted mites
The mite is another insect that
prefers warm, dusty conditions
over the summer period
and has been causing some
concerns in horticultural crops
recently. Two-spotted mites
(Tetranychus urticae) thrive in
these conditions and can be
easily spread by wind and on
i
clothing, machinery and birds,
and have been more active
than normal in recent weeks.
The adult Two-spotted mite
has an oval-shaped body
about 0.4mm long. It has
eight legs and a characteristic
dark spot on each side of the
body. Its eggs are round and a
translucent pale yellow when
laid; as they develop, they
become reddish. They are
often deposited in clusters on
the under surface of the leaf.
When monitoring, pay
particular attention to cropping
areas that are dusty; for
example, farm tracks, laneways
and ends of rows.
For more information or to ask a question, please contact your local
Syngenta Territory Manager, the Syngenta Advice Line on 1800 067 108,
visit syngenta.com.au or email Vegetables Australia:
info@ausveg.com.au. Please note that your questions may be published.
The R&D content for this article has been provided to Vegetables
Australia to educate Australian vegetable growers about the most relevant
and practical information on crop protection technologies and their
on-farm applications. This communication was funded by Horticulture
Innovation Australia Limited using the National Vegetable Levy and funds
from the Australian Government.
Project number: VG15027
Two-spotted mite.
Photo courtesy of David
Cappaert, Michigan State
University, Bugwood.org.
Potato moth.
Image courtesy of Central Science Laboratory,
Harpenden, British Crown, Bugwood.org.