Issue Number: 05
Date: 13/06/2014
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 National Invertebrate Pest Initiative (NIPI) a Grains
Research and Development Corporation (GRDC) project that promotes national pest management
information and Integrated Pest Management (IPM) principals.
Newsletter of the Department of Agriculture and Food, Western Australia
Contents
Mites and lucerne flea
Barley net blotch
Wheat leaf spot diseases
Downy mildew
Lupin root and hypocotyl disease
Ring spot on wheat
Snails and slugs
European earwigs
Caterpillars
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.
Mites and lucerne flea
Sam Repacholi (Landmark) reports seeing redlegged earth mites (RLEM) for the first time this
season in the Salmon Gums area. The mites are damaging a small patch of 2–4 leaf canola crop
south of Salmon Gums. According to the Department of Agriculture and Food, Western Australia
(DAFWA) RLEM model produced by Moin and Kawsar Salam, there was favourable conditions for
hatching at Salmon Gums in the week of 13th May, these mites are now approaching adult size
and are more easily seen.
Matt Willis (Elders) reports seeing redlegged earth mites in a number of cereal crops in the
Koorda and Wyalkatchem area, he noticed quite a few smaller mites amongst the larger ones,
which may indicate a staggered hatching. The mites aren’t causing any significant damage at this
stage so the crops will continue to be monitored.
Wayne Smith (Agronomic Acumen) reports that he is noticing an increase in balaustium mites in
canola crops along the south coast and in the Kojonup area.
Chloe Bairstow (Landmark) reports that lucerne flea are still damaging some of the 2–3 leaf cereal
crops in the Lake Grace area, there are also redlegged earth mites causing damage to some
crops in the area.
John Moore (DAFWA) reports that a lucerne crop at Kojonup had 10% of the leaf area damaged
by lucerne flea feeding.
A consultant reports that lucerne flea are causing damage in a number of canola crops in the
Merredin area at a level that has required control sprays to be applied.
An agronomist reported to northern agricultural region DAFWA staff that lucerne flea are still
causing some problems in a few locations in the Dalwallinu area. The agronomist noted that
some crops had been checked for damage and looked good only to be rechecked at a later date
to find heavy lucerne flea damage. The agronomist commented that the delay in follow up
monitoring is probably a function of larger cropping programs in the area this year resulting in less
frequent observations in all paddocks.
This highlights the importance of crop monitoring at regular intervals, particularly in the weeks
following germination and later in the season prior to and following pod/grain formation. Many
insect pests in their small nymphal or juvenile stages cause relatively minor damage that may go
unnoticed, giving the impression of low pest pressure. As the pest approaches the adult stage the
amount of damage they can inflict on a crop can increase considerably hence infrequent checking
can result in what appears as sudden damage when in fact it has occurred over several weeks.
Barley net blotch
Ty Henning (TekAg) has seen widespread barley net blotch while inspecting barley crops in the
Maya, Buntine, Dalwallinu and Pithara areas. Northern Agricultural Region (NAR) DAFWA staff
have had reports from another agronomist of net blotch on 4-5 leaf barley crops in Dalwallinu
which have received a fungicide spray.
Chloe Bairstow (Landmark) reports spot type net blotch infections are common in a lot of early
sown barley crops in the Lake Grace area, some infections are quite severe and are holding back
the growth of the crop, requiring an early fungicide application. The net blotch problem appears
worst in paddocks where the crop is next to infected stubbles in neighbouring paddocks that have
not been burnt.
DAFWA plant pathologist Ciara Beard has observed spot-type net blotch on Hindmarsh barley at
Eradu in a trial at 5 leaf stage. It is a second year crop that was also sown to Hindmarsh last year,
and it is interesting to note that at this stage the buffers of the trial (first time sown Hindmarsh) are
not showing any signs of spot-type net blotch at this stage. The trial won’t be sprayed with
fungicide until Z37 and then only if the disease is spreading up the canopy.
Though spot-type and net-type net blotch can look ugly, the main determinant of whether they are
likely to lead to significant yield loss appears to be seasonal rainfall. These diseases can cause up
to 20 – 30% yield loss in medium to high rainfall seasons and are commonly yield limiting in areas
such as the southern agricultural region (SAR). Ciara’s research over many years in the northern
agricultural region (NAR, 2003-2009) has shown that fungicide application for either net-type or
spot-type or mixture of both in feed varieties is rarely worthwhile in terms of yield gain, with only
two out of her 10 trials having a significant yield response from fungicide. Most of the time the
fungicide did significantly reduce disease levels but this did not translate to yield benefits (average
yield of untreated across the 10 trials was 1.6 tonnes per hectare (t/ha). Fungicide application did
however result in quality benefits such as reduced screenings. Geoff Thomas has had similar
results with his trials in the central agricultural region, however he commented that last year with
the above average wet spring some growers achieved good yield responses from applying
fungicide for net blotch in barley. In the SAR, DAFWA plant pathologist Kith Jayasena has found in
his trials from 1999–2003, that fungicide application was effective at reducing disease
(predominantly spot-type net blotch) and increasing yield and grain quality in eight out of nine of
his trials (average yield of untreated across his trials was 3.7 t/ha and many were malting grade).
Applying a fungicide spray is necessary in medium to high rainfall regions where disease
threatens crops with high yield and quality expectations, particularly if the barley crop has been
sown into or adjacent to last year’s barley stubble. The choice of a single-spray or two-spray
strategy depends on the environment in which the crop is growing. In high rainfall environments it
may be necessary to apply two sprays, such as at early stem elongation stage with a follow-up
spray three to four weeks later.
While in medium rainfall regions, consider one well timed spray between late stem elongation and
early flag leaf emergence (Z33 - 39) to protect leaf 2 (flag-1). Under high disease pressure, best
results may be obtained by using the maximum recommended rates.
Net-type net blotch Infection and spread is favoured by wet conditions and it is most evident
following periods of rainfall. It will cause the greatest yield loss in paddocks that are re-sown to
barley without a break-crop as the fungus is stubble borne, carried from season to season on
infected barley stubbles. Spores produced on stubble are spread by wind to initiate infections in
new barley crops. Seed infection is rare and is considered of minor importance in spreading
disease.
Spot-type net blotch is stubble and seed borne, like net-type net blotch. However the importance
of seed infection in initiating seasonal epidemics is not known. Spot-type net blotch occurs statewide but is most damaging in south coastal and neighbouring medium to high rainfall regions
where it can have severe yield and quality effects.
For information on symptoms and management of net blotch, see the Managing net type net
blotch and spot type net blotch in Western Australia webpage, which is available along with other
disease management information including Registered foliar fungicides for cereals in Western
Australia, publications on specific diseases, variety disease ratings, disease forecasts and
instructions for submitting plant samples on the crop disease page on the DAFWA website.
Wheat leaf spot diseases
Ty Henning (TekAg) has commented that yellow spot in wheat is becoming more noticeable in the
Maya, Buntine, Dalwallinu and Pithara areas.
DAFWA plant pathologist Ciara Beard has observed yellow spot/septoria nodorum blotch on very
early (April) sown susceptible wheat varieties in research plots in Geraldton.
Septoria nodorum blotch and yellow spot frequently occur together throughout the wheatbelt and
are very hard to distinguish with the naked eye due to almost identical symptoms. They have the
capacity to significantly reduce yield by up to 30% and also reduce grain quality. Impacts from leaf
spot diseases vary greatly from season to season and between locations. They are particularly a
problem in continuous wheat crops in stubble retention farming systems as these diseases are
stubble borne. For wheat after wheat, when there is high disease pressure prior to stem
elongation, DAFWA research has shown it may be economic to apply fungicide at, or prior to,
early stem elongation (Z31, first node) particularly in medium to high rainfall areas where the crop
is struggling with a heavy disease burden. A second spray may be required at or after flag leaf
emergence.
For further information on identifying and managing these diseases refer to Managing yellow spot
and septoria nodorum blotch in wheat DAFWA webpage.
Downy mildew
Ty Henning (TekAg) reports that downy mildew still affecting some canola crops in the Dalwallinu
area, especially with the cooler weather slowing plant growth. The downy mildew was most
noticeable in areas of crops with poor nutrition.
Plant Pathologist Ravjit Khangura (DAFWA) reports that she has noticed downy mildew symptoms
on the true leaves in the Great Southern Region. Downy mildew is affecting usually the first true
leaves causing yellowing and consequently accelerating leaf senescence.
Ravjit comments symptoms of downy mildew on true leaves appear mostly as angular to irregular
yellow patches on the upper leaf surface with sparse downy growth of the fungus on the
corresponding under surface. Sometimes, symptoms may be restricted to leaf margins with white
to creamish lesions. In severe cases, several lesions coalesce and cause premature senescence.
Cool wet conditions favour secondary spread by sporangia. Plants normally grow out of disease
once they achieve 5–6 leaf stage. Ravjit says downy mildew in general is not likely to cause major
economic losses but some yield loss may be expected in crops where heavy seedling infection
caused reduced vigour and poor growth. A copper fungicide (350 grams per litre (g/L) cupric
hydroxide) is registered for foliar application against downy mildew in canola, available as Cung
Fu 350 SC Fungicide® (registration till June 2014).
For more information on downy mildew see PestFax No.2 23 May 14 and for diagnosing
symptoms and management options refer to Diagnosing downy mildew in canola webpage.
Lupin root and hypocotyl disease
Peter Norris (Agronomy For Profit) reports a crop of lupins at East Walkaway badly affected by
rhizoctonia, predominantly hypocotyl rot but with root rot present also. The paddock was
established with no till disks and Rovral seed dressing applied. On the lighter soil areas of the
paddock which are worst affected, establishment is probably reduced by up to 60%.
Plant Pathologist Bill MacLeod says that the strains of Rhizoctonia causing hypocotl rot and root
rot are related but cause different symptoms. He says that the majority of fungal inoculum of
hypocotyl rot can be found in the top 5 centimetre (cm) of soil where it can survive for at least two
years in remnant organic matter.
The greatest risk of infection by hypocotyl rot is associated with very early sowing into warm soil in
paddocks with known disease risk. This risk can be exacerbated where a glyphosate herbicide is
used immediately prior to seding,especially on light soils.
Nothing can be done in this paddock this season to stop the disease, however in future years,
avoiding very early sowing, shallow sowing to reduce exposure of the hypocotyl to the fungal
inoculum and increasing sowing rate can compensate for establishment losses in high risk
paddocks.
Ring spot on wheat
Matt Willis (Elders) reports that two paddocks of Z15, 21 Calingiri wheat north of Koorda are
infected with ring spot. Both were in pasture last year with high levels of grassy weeds and no
action will be taken. DAFWA Plant Pathologist Dr Kith Jayasena agrees that the yield impact
would be negligible and that no action is required.
For further information see Ring spot in cereals.
Snails and slugs
Wayne Smith (Agronomic Acumen) has noticed that the number of paddocks with snails on farms
on the south coast is increasing every year. Luke Marquis (SE Agronomy Services) reports that in
the Esperance to Ravensthorpe region there has now been sufficient moisture for snails to be
actively moving and feeding.
Luke Marquis (SE Agronomy Services) reports that a canola crop up to the three 3 leaf stage at
Hopetown has had significant slug damage. The damage is patchy but at least 10% of the crop in
the paddock has been consumed.
Svet Micic (DAFWA) commented that now is a good time to reapply or apply baits to protect at risk
crops from feeding damage from snails and slugs. However, baits will compete with green plant
material to attract pests, so it can be difficult to get good control. Increasing baiting rates will help
suppress the damage. Another thing to bear in mind, come harvest, is that if snails have not been
controlled, harvested grain may contain snails and may need to be cleaned to meet grain delivery
standards.
For further information on snails refer to PestFax issue No.1 16 May 14 and to the GRDC Snail
Management Fact Sheet and Identification and control of pest slugs and snails for broadacre
crops in WA
European earwigs
Luke Marquis (SE Agronomy Services) reports that at Wittenoom Hills European earwigs have
caused significant damage to a canola crop that is at seedling to the 3 leaf stage. The damage
consists of seedlings being chewed to the ground, and has occurred in crop rows that are adjacent
or in close proximity to chaff rows. The earwigs are sheltering under the chaff rows and moving out
from these shelter sites to feed on the crop. Damage is patchy but widespread. European earwigs
can be difficult to control. Trials have shown that applying the highest registered rate of
chlorpyrifos or alpha-cypermethrin in cereals when earwigs are active at night has decreased
numbers.
Caterpillars
Ty Henning (TekAg) reports that caterpillars have been found damaging canola and cereal crops
in the Maya, Buntine, Dalwallinu and Pithara areas. Most of the caterpillars are small, less than
one centimetre and in relatively low numbers at present.
Matt Willis (Elders) has been finding high numbers of pasture day moth caterpillars in cereal crops
in Koorda and Wyalkatchem. The grubs are feeding on capeweed and currently not causing any
significant damage to the crop. They are not usually considered a pest as they prefer to feed on
capeweed and other broadleaved plants. However, pasture day moth caterpillars have been
known to feed on crops and pastures in the absence of these preferred plants, especially when
weeds are destroyed by herbicides.
Also available:
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 Departmental 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? Send in your digital pictures (in focus) or send
live specimens in a non-crushable plastic jar for free identification. Mail to Peter Mangano or
Svetlana Micic at the postal details above.
IPM Guidelines for grains
AgTactic and AgMemo
Other regional DAFWA news updates are available on DAFWA’s website.
Growing Season Outlook
Seasonal climate outlooks are available on DAFWA’s website.
AGWEST Plant Labs
Plant disease diagnostic service 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 our
website or the AgWest plant laboratories webpage.
Next issue of PestFax – 20 June 2014
Copyright © Western Australian Agriculture Authority, 2014
The Chief Executive Officer of the Department of Agriculture and Food and the State of Western Australia accept no
liabilitywhatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.