Issue number: 21
Date: 03/10/2014
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
Omethoate tolerance in redlegged earth mites
Cold induced sterility in wheat heads
Native budworm
Correction to charcoal rot location
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.
Omethoate tolerance in redlegged earth mites
DAFWA Entomologists have confirmed tolerance of redlegged earth mites (RLEM) to the widely
used insecticide omethoate (e.g. Le-mat™, Omethoate 290™) after an agronomist and farmer
near Capel reported poor control of the mites following spray applications. The RLEM on the
affected paddock were also confirmed to have resistance to the synthetic pyrethroid (SP) group of
chemicals (e.g. Talstar™, Alpha-cypermethrin etc.)
Western Australia (WA) is the only known state with RLEM resistance to the SP group of
insecticides. The first case of SP resistance was discovered near Esperance in 2006 and since
then over 30 properties in WA have been found with mites that are highly resistant to SP
insecticides. Until now the organophosphate (OP) group of chemicals (includes omethoate) have
been the mainstay alternative chemical group providing effective control of RLEM.
The discovery was made as part of a national research project funded by the Grains Research
and Development Corporation (GRDC) in conjunction with DAFWA, University of Melbourne and
Supporting your success
cesar, CSIRO and University of Western Australia. The project is investigating the extent of RLEM
resistance, mechanisms responsible for its development, alternative chemicals and resistance
management strategies against this important and widespread pest of southern Australian
agriculture.
The paddock where these tolerant mites were found is a high production paddock, that has had
repeated sprays of SP and OP insecticides over many years.
Entomologist Svet Micic said that laboratory bioassays (jar tests) found the Capel mites were
14 000 times more tolerant to omethoate than a population of RLEM that had never been sprayed.
This compares with RLEM resistance to bifenthrin which is 240 000 times more resistant than
susceptible populations of mites. This means that registered rates of omethoate and high rates of
SPs failed to adequately control redlegged earth mites at the Capel property.
At this stage it is not known if the omethoate tolerance is persistent. The SP resistance has been
found to be heritable, persisting after several generations in affected paddocks and after culturing
in laboratories.
It is unlikely that the Capel property is a rare case – preliminary testing of a property near Boyup
Brook last week is also indicating that omethoate tolerance / SP resistance is present in isolated
RLEM populations. Although most farming properties in WA still have excellent control of RLEM
using the cost effective SP and OP chemical groups the recent finding brings into question how
long will they remain effective? and what is the best management strategies to prolong their use?
The incorporation of insecticides into tank mixes for weed or disease control or a fertiliser spray is
very useful as it saves on application costs; however the routine and over-use of insurance sprays
will inevitably lead to higher selection pressure on insects and mites and is very likely to accelerate
resistance development. Svet advises growers to assess the economic risk of pest damage before
making spray decisions and where practical rotate chemical groups within and between seasons
to minimise potential resistance build-up on properties.
Growers who notice RLEM that survive any insecticide sprays please contact Svetlana Micic
(Albany) on +61 (0)8 9892 8591, Alan Lord (South Perth) +61 (0)8 9368 3758 or Peter Mangano
0404 819 534 to arrange for free resistance testing.
Further information is available by visiting the DAFWA webpage prevent redlegged earth mite
resistance.
Cold induced sterility in wheat heads
Michael Durant (Landmark) reports finding misshapen wheat heads, on a Mace wheat crop north
of Cranbrook. On closer examination some of the forming wheat grains are missing or
underdeveloped. He also heard reports of similar symptoms in wheat crops in the Nyabing area.
Frost damage was suspected as the cause of the disorder, however the paddock is not normally
considered to be prone to frost. Wheat heads showing the symptoms have been found on top of a
hill with a loamy soil type and good soil moisture over the last few weeks. The location of the
affected flowers in the head is random, this also suggests that frost is unlikely. Some heads have
up to 10-12 grains missing while others don’t have any missing.
Jeremey Lemon (DAFWA) has examined some of the crops with Michael and noticed that the
female parts on affected flowers is white and fluffy and is sitting on top of a quarter grain which
has a healthy white/green appearance. However it hasn’t developed at anywhere near the rate of
other grains in the head.
DAFWA weather station minimum temperatures below 2 degrees Celsius were recorded at
Tunney, North Stirling, and Woogenellup on 31 August, 3, 13 and 15 September. Minimum
temperatures at Nyabing on these dates were 0.2 on 31 August and between 2.0 and 2.5 on the
September dates.
DAFWA frost researcher Ben Biddulph looked at photos and commented that it looks like frost
induced sterility/cold induced sterility. Ben’s group sees these types of symptoms in their trials and
frost nurseries all the time. Most growers don't notice it as they don't look that closely. Trials have
shown that temperatures below 2 degrees Celsius can start to cause it. Ben commented that it is
not known exactly when the crop is most susceptible but thinks it is during pollen meiosis or young
microspore of the developing anther. Controlled environment work with three day cold treatments
at 1 degree Celcius conducted in collaboration with CSIRO indicates it can be triggered by cold
anywhere from Z 39-65 (flag leaf ligule just visible to mid anthesis), with a slight increase at Z 4145 (flag leaf sheath extending to boots swollen) but this depends on variety and growth conditions.
Wyalkatchem type varieties are more susceptible.
Figure 1 Misshapen wheat heads
Native budworm
Native budworm moths are continuing their south-westward flights into crops: moth flights
recorded weekly in pheromone traps by volunteer farmers and DAFWA staff show that moth
numbers have increased significantly in some areas. Notably higher numbers of moths have flown
into crops in recent weeks at Cuballing, Kellerberrin, Kojonup, Narrogin and Pingrup: see
Native Budworm Moth Trap Numbers 2014.
Some pulse and canola crops remain at risk of damage by native budworm caterpillars whilst the
pods have some suppleness and the seeds are not dry and hard. Big budworm grubs (30-40
millimetres long) will chew into quite firm seed pods whilst younger grubs with less developed
mouth parts will find it more difficult. Most of the damage to canola and lupin crops by budworm
takes place in the two to three week window between leaf senescence and when the pods
become firm-dry to hard. This is in contrast to field peas, faba bean, lentils and other pulse crops
that are at risk of damage for a much longer time from initial pod formation until maturity and
drying of seeds.
Crops in south western high rainfall locations (especially late sown crops) may be vulnerable to
damage and these crops will need to be checked, using a sweep net at several locations in the
crop, to determine if numbers are below spray threshold levels. Eggs laid by newly arriving moths
into crops that are only a few weeks from harvest will not be of any consequence as the hatching
and developing grubs will be too small to do any damage before the crop dries off.
For further information on native budworm visit the webpage: Management and economic
thresholds for native budworm.
Pesticide options for the control of native budworm can be found in the Winter/Spring Insecticide
Spray Chart 2014.
For information on insecticide withholding periods refer to PestFax Issue 20 26/09/2014
Correction to charcoal rot location
In last week’s PestFax charcoal rot was reported occurring in E. Buntine, this was incorrect it
should have been E. Ballidu.
List of registered insecticides
A list of registered insecticides to control winter/spring pests on canola, lupins, cereals, field peas
and pastures is available on the PestFax webpage: Winter/Spring Insecticide Spray Chart 2014
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 9892 8591 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 – 10 October 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