Issue Number: 14
Date: 15/08/2014
PestFax
PestFax is a weekly informative and interactive reporting service, providing risk alerts, current
information and advice on pests and diseases threatening crops and pastures throughout the grain
belt of Western Australia (WA).
PestFax is supported by the Grains Research and Development Corporation (GRDC) and
promotes national pest management information and Integrated Pest Management (IPM)
principals.
Newsletter of the Department of Agriculture and Food, Western Australia (DAFWA)
Contents
Cereal aphids
Canola aphids
Diamondback moths
Native budworm moths
To view a map of pest and disease reports, see PestFax Map and PestFax newsletters for back
copies of PestFax. If you have recently observed or heard news of insect or disease pests in crops
and pastures contact PestFax@agric.wa.gov.au or use the online ‘make an on-line report’ link.
Cereal aphids
Rob Campbell (Landmark) found oat aphids increasing in numbers last week on a Baudin barley
crop near Mingenew. The crop is in the late stem elongation growth stage (GS 35-39) and has
11-20% of the tillers infested with colonies of oat aphids.
A grower reported to PestFax that inspections of cereal crops near Beverley are revealing
increasing numbers of cereal aphids. Some growers are concerned levels are rising to
economically damaging levels that may require spray control.
Department of Agriculture and Food entomologist Darryl Hardie reports finding cereal aphids in
clusters on the stems and the back of leaves in patches along the edge of a wheat crop between
York and Beverley.
Supporting your success
In most cereal growing areas aphids may be found on parts of the crop but they usually remain at
low numbers without the need for chemical intervention. Regular monitoring of cereal crops to
determine changes in aphid populations and waiting until close to threshold levels of aphids before
spraying is the recommended practice. Crop inspections at several locations around cereal
paddocks is recommended as aphid density will vary within crops. Look on the stems, undersides
of leaves and in the furled growing tips for clusters of aphid colonies.
Naturally occurring parasitoids and predators such as wasps, lacewings and ladybird beetles often
suppress aphid populations and the unnecessary spraying of ‘anti-feed’ synthetic pyrethroid
sprays will only counteract their benefits.
Threshold
Spraying for cereal aphid feeding damage is considered worthwhile if 50% of tillers have at least
15 aphids and crops have a yield potential of greater than 3 tonnes per hectare (t/ha). Yield losses
of up to 10% from aphid feeding damage have been recorded in DAFWA trials, with an associated
reduction in grain quality (shrivelled grains) if aphid damage occurs late season.
In order to maximize the benefit of spray control against aphid feeding damage crops need to be
sprayed whilst populations are on the increase (often over a period of five weeks or more) and
before they reach their peak levels. Due to the unpredictability of aphid population change,
spraying for aphids by growers can occur as the populations are peaking and just before a natural
decline occurs. Spraying at this late stage will have limited or no benefit in protecting yields.
Where cereal aphid populations have been rising over a number of weeks the level of natural
biocontrol agents, such as parasitic wasps, usually also increase and help to contain or reduce the
aphid levels.
Further information on control of cereal aphids can be found in the GRDC cereal aphid factsheet,
at the DAFWA webpage: Aphid feeding damage to cereal crops and the Winter/Spring Insecticide
Spray Chart 2014.
Canola Aphids
Rob Campbell (Landmark) reports finding low levels of canola aphids in a late flowering Hyola 404
canola crop north west of Carnamah. Rob identified the aphids as cabbage aphids which are
currently being found on less than 1% of flowering spikes. The aphids were predominately winged
aphids which were confined to areas of crop that were under moisture stress, especially on
sandier soils. Along with the aphids were beneficial insects that will hopefully help to limit the aphid
populations.
Grant Thompson (Crop Circle Consulting) reports finding moderate numbers of aphids, including
green peach aphids, in canola crops in the Greenough and Walkaway areas.
There are two species of aphids, the cabbage aphid and the turnip aphid, which can cause
damage by feeding on canola.
Threshold
The threshold for aphid feeding damage to canola crops is 20% of flowering plants infected with
aphids. The feeding damage by aphids is increased if crops are suffering from drought stress. If
spraying is required, a border spray may suffice for cabbage aphids, which can often be found
within 20-30 metres (m) of the crop edge.
For further information refer to the Aphid management in canola crops and the Winter/Spring
Insecticide Spray Chart 2014.
Diamondback moths
Grant Thompson (Crop Circle Consulting) reports diamondback moth (DBM) numbers are ramping
up in the Greenough and Walkaway areas. Grant sweep netted a number of canola crops in
these areas and found up to 100 DBM caterpillars per 10 sweeps. The canola crops are slightly
moisture stressed but have very good yield potential. A control spray will be applied to reduce
caterpillar numbers.
When DBM populations are in high numbers they often require control with at least one spray and
often two successive sprays. In many years and for most canola growing areas levels of DBM
caterpillars remain low and do not usually reach damaging levels that require control. Monitoring
for DBM in canola crops by routinely using a sweep net during flowering/podding growth stage is
the only sure way to be confident of pest population changes over time and therefore enable
informed management decisions.
For more information on DBM and its control refer to the GRDC Factsheet: Diamondback moth in
canola and the Winter/Spring Insecticide Spray Chart 2014.
Native budworm moths
Flights of native budworm moths continue to be detected in pheromone traps throughout many
parts of the Western Australian grainbelt. Catches for the last week include Badgingarra (42
moths), Cowcowing (18), Cunderdin (8), Doodlakine (219), Eradu (89), Greenough (18),
Kirwan (71), Maya (9), Merredin (34), Mollerin (25), Varley (12), Wubin (7).
Matt Willis (Elders) used a sweep net to monitor a canola crop near Mollerin this week and found
nine bud worm caterpillars per 10 sweeps (five grubs at 0-5mm, three grubs >5-10mm, one
grub >10mm), Matt also checked a canola crop near Cowcowing and found about one caterpillar
per 10 sweeps.
The trap numbers only provide an indication of the pests’ activity and cannot be relied upon for
control decisions – only the use of a sweep net to regularly check crops can give growers
confidence in the levels of budworm present.
For further information on native budworm visit the webpage Management and economic
thresholds for native budworm.
Also available:
List of registered insecticides
A list of registered insecticides to control autumn/winter pests on canola, lupins and cereals is
available on the PestFax webpage: Autumn Winter Insecticide Guide 2014.
Crop insects: the ute guide
This book covers crop pests, beneficial insects, biological control, grain storage pests and
biosecurity pest threats specific to WA. Copies are available from some DAFWA offices for a cost
of $10.00 or by mail order by phoning the DAFWA South Perth office on +61 (0)8 9368 3710.
Free insect identification
Having troubles identifying mites or other pests? For free identification, send your digital pictures
(in focus) or live specimens (in a non-crushable plastic jar) to Peter Mangano or Svetlana Micic at
the postal details below.
Svet Micic, DAFWA Albany
444 Albany Highway,
Albany WA 6330
Email: svetlana.micic@agric.wa.gov.au
Phone: +61 (0)8 98928591 or +61 (0)427 772 051
Peter Mangano, DAFWA South Perth
3 Baron-Hay Court,
South Perth WA 6151
Email: pmangano@agric.wa.gov.au
Phone: +61 (0)8 9368 3753 or +61 (0)404 819 534
Integrated Pest Management Guidelines for grains
AgTactics and AgMemo
Other regional DAFWA news updates are available on DAFWA website.
Seasonal climate outlook
Seasonal climate outlooks are available on DAFWA website.
AGWEST Plant Labs
Plant disease diagnostic services are located at the DAFWA South Perth office. For information on
sending samples and charges contact +61 (0)8 9368 3721 or Fax +61 (0)8 9474 2658 or visit the
DAFWA website or the AGWEST Plant Laboratories.
Next issue of PestFax – 22 August 2014
Important disclaimer
The Chief Executive Officer of the Department of Agriculture and Food and the State of Western
Australia accept no liability whatsoever by reason of negligence or otherwise arising from the use
or release of this information or any part of it.
Copyright © Western Australian Agriculture Authority, 2014