Cereal aphid species need to be correctly identified
Research scientist Grace Williams (DPIRD) has recently found corn aphids in booting La Trobe barley near Merredin.
Entomologist Dustin Severtson (DPIRD) has recently reported finding low levels of oat aphids in a wheat crop near Nunile.
Cara Allan (Syngenta) has also recently found corn and oat aphids in a barley trial near York. The plants were the booting growth stage.
Research scientist Kylie Chambers (DPIRD) reports finding oat aphids recently in Highbury and Katanning oat crops.
Identifying cereal aphids
It is important that growers, consultants and agronomists correctly distinguish between cereal aphid species for effective aphid management.
The Russian wheat aphid was recently detected north of Esperance. For more information on this exotic pest refer the 2020 PestFax Issue Russian wheat aphid found in Esperance region.
Growers, consultants and agronomists are encouraged to request aphid identification or report any suspect detections of RWA or RWA damage to the DPIRD Pest and Disease Information Service on +61 (0)8 9368 3080. Alternatively you can report by using the MyPestGuide™ Reporter app, PestFax Reporter app or MyPestGuide™ Reporter web page.
Reporting the absence of RWA or RWA symptoms is just as important as reporting the presence of the aphid or symptoms.
Managing cereal aphids
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.
Direct feeding damage from aphids occurs when colonies of aphids develop on stems, leaves and heads, usually in the tillering and later stages of crop growth through to head filling. The degree of damage depends particularly on the percentage of tillers infested, the number of aphids per tiller and the duration of the infestation. If low numbers of aphids are observed, wait until threshold levels are reached before considering control options.
Barley crops are most at risk from aphids due to the possibility of downgrading from malt to feed quality, as aphid feeding damage can cause grain shrivelling. If 50 per cent of tillers have 15 or more aphids then the feeding damage may cause reductions in yields by up to 10 per cent and also reduce grain size.
Keep in mind that naturally occurring parasitoids and predators such as wasps, lacewings and ladybird beetles will also increase with warming weather. These predators can keep aphid populations below threshold levels and un-necessary spraying of “anti-feed” synthetic pyrethroid sprays will only counteract their benefits.
When spraying, consider spray options that are soft on predators.
Also dense aphid colonies are prone to fungal pathogens. Aphids infected by fungi are sluggish and have white to yellow ‘fur’ covering their bodies. The fungus can readily spread throughout aphid colonies. The fungus especially is more effective in decreasing aphid populations than chemical control.
For a list of insecticides registered for use on aphids see DPIRD’s 2020 Winter Spring Insecticide Guide.
For more information on cereal aphids refer to DPIRD’s;
- 2020 PestFax Issue 9 Cereal aphids article
- Diagnosing cereal aphids page
- 2017 Protecting WA Crops Issue 3 newsletter Aphids – WA’s insect problem children.
For more information on aphids contact Svetlana Micic, Research scientist, Albany on +61 (0)8 9892 8591 or Alan Lord, Technical officer, South Perth on +61 (0)8 9368 3758.
Article authors: Cindy Webster (DPIRD Narrogin) and Svetlana Micic (DPIRD Albany).
Article input: Alan Lord (DPIRD South Perth) and Bill Trend (DPIRD South Perth).
Diamondback moth numbers have increased at Esperance
- Mount Ridley
An agronomist has reported sweep netting more than 100 diamondback moth (DBM) caterpillars per 10 sweeps in an early flowering canola crop near Cunderdin. This was in a paddock hotspot but low numbers of DBM were in surrounding canola crops in the area. A control spray will be applied to the paddock.
Claire Johnston (Elders) reports that generally low numbers of DBM caterpillars are being found in canola crops in Dalwallinu and surrounding areas. With warmer spring weather, it is anticipated that numbers will increase in coming weeks.
A DBM surveillance project funded by GRDC, led by DPIRD, is using DBM pheromone traps to predict where DBM are in the landscape (see map above). Each trap is located within a canola crop. Traps located in the Esperance area are capturing higher numbers of DBM than traps located elsewhere. Indicating that canola crops in the Esperance region should be monitored for DBM caterpillars.
Rob Hughes (SEAR) has found 216 DBM moths on his sticky trap and an average of 8 DBM caterpillars in 10 sweeps in the adjacent canola crop at a site near East Condingup.
Technical Officer Joel Kidd (DPIRD) found 60-160 DBM moths on sticky traps at three sites around Gibson. In the adjacent canola crops, DBM caterpillars were in low numbers, well below thresholds.
If you are sweep netting canola crops for DBM caterpillars please use the PestFax Reporter app to report and share your findings. It will help the DBM surveillance project team to determine how well the pheromone traps have worked in predicting where DBM are.
Managing DBM later in the season
DBM thresholds for control are:
• Early to mid-flowering (no stress) - 50 caterpillars or more per 10 sweeps
• Mid to late flowering (no stress) - 100 or more caterpillars per 10 sweeps
• Pod maturation - 200 or more caterpillars per 10 sweeps.
Moisture stressed crops are more susceptible to insect damage, so a lower threshold may be used if extended dry periods are experienced.
DBM have less impact on yield once canola crops stop flowering. Visual surface grazing and scarring of pod walls and stems will occur from DBM caterpillar feeding late season and this may result in a minor reduction of grain filling capacity depending on numbers of grubs, soil moisture levels and length of time to harvest.
Growers are urged to abide by label withholding periods for swathing/harvesting canola if applying a registered insecticide to control DBM (see the table below).
|Active ingredient||Withholding period (days)|
The pyrethroids (alphacypermethrin, esfenvalerate, gamma and lambda cyhalothrin) and carbamate (methomyl) registered for DBM are known to provide poor kill on DBM populations because of insecticide resistance.
Pesticide options for the control of native budworm and DBM can be found in DPIRD’s Winter/Spring Insecticide Spray Chart 2020.
For more DBM information refer to:
- DPIRD’s 2020 PestFax Issue 8 Native budworm and diamondback moths are being found across the wheatbelt article
- DPIRD’s Diagnosing diamondback moth page
- GRDC's Diamondback moth fact sheet
- GRDC’s Managing diamondback moth video.
For more DBM information contact Alan Lord, Technical Officer, South Perth on +61 (0)8 9368 3758 or Svetlana Micic, Research Officer, Albany on +61 (0)8 9892 8591 or Dustin Severtson, Development Officer, Northam on +61 (0)8 9690 2160.
Article authors: Cindy Webster (DPIRD Narrogin), Alan Lord (DPIRD South Perth), Svetlana Micic (DPIRD Albany).
Article input: Amber Balfour-Cunningham (DPIRD Northam) and Dusty Severtson (DPIRD Northam).
How to distinguish Fall armyworm caterpillars from other endemic caterpillars
With the recent detection of a fall armyworm (FAW) moth at Geraldton it is important that growers and consultants are able to distinguish fall armyworm caterpillars from other common caterpillars that may appear similar in appearance. For example, budworm caterpillars that are commonly found in the grainbelt can appear in variable colours, similar to the FAW caterpillar.
Distinguishing fall armyworm caterpillars from the usual armyworm caterpillars
Common armyworm caterpillars have three white stripes on their collar. The FAW differs from our endemic species of armyworm by having a spotted pattern of dots and a distinctive inverted white Y (see figure 1) which the common armyworm caterpillars do not have (Figure 2). FAW can also be found on pulse and canola crops which are not hosts for common and southern armyworm.
Distinguishing fall armyworm caterpillars from budworm caterpillars
FAW caterpillars can be confused with the native and lesser budworm caterpillars. FAW caterpillars, like budworm caterpillars, can appear in a range of colours. However, budworm caterpillars do not have a distinctive Y marking on the head area, as seen in Figure 3.
What should you do if you suspect you have found FAW?
If you find a caterpillar that you suspect to be FAW please collect a sample. Place the caterpillar into boiling water for approximately 5 minutes as this denatures enzymic activity. Then place the caterpillar into 70% ethanol or methylated spirits and contact DPIRD entomologist Dusty Severtson on +61 (0)427 196 656 to arrange for identification.
You can also take clear close-up photos of the caterpillar and plant damage and submit a report using the MyPestGuide Reporter app or contact DPIRD’s Pest and Disease Information Service (PaDIS) by email or phone +61 (0)8 9368 3080. Samples may then be requested as the only way to make a definitive identification for FAW is from examining a physical specimen. DPIRD entomologists cannot make a definitive identification from images.
For more information on FAW refer to DPIRD’s;
- Fall Armyworm in Western Australia page
- Fall armyworm larval identification guide fact sheet
- How to identify fall armyworm video
- 2020 PestFax Issue 10 Fall armyworm detected in the WA grainbelt article.
For more information contact Dustin Severtson, Research scientist, Northam on +61 (0)427 196 656.
Article authors: Cindy Webster (DPIRD Narrogin), Svetlana Micic (DPIRD Albany) and Alan Lord (DPIRD South Perth).
Remember to sweep net crops for native budworm caterpillars
Native budworm caterpillar activity
- Narra Tarra
Joanne Walker (DPIRD) reports finding one budworm caterpillar (5mm) per 10 sweeps in a lupin crop near Narra Tarra.
An agronomist has reported finding two budworm caterpillars (5-10mm) per 10 sweeps in a canola crop west of Dalwallinu.
A farmer near Doodlakine has found five budworm grubs per ten sweeps in a lupin crop.
A farmer south of Kellerberrin reports finding two grubs (5-15mm) per 10 sweeps in a lupin crop, but found no caterpillars in a nearby canola crop.
A budworm trapper near Maya reports finding 1 budworm caterpillar per 10 sweeps in a field pea crop. The size of the caterpillars captured during the sweep netting varied between 10 and 30mm. He also commented that he had noticed a few of pods that had been damaged by budworm caterpillar feeding.
Field pea, chickpea, lentil and faba bean crops are very susceptible to all sizes of caterpillars during the formation and development of pods. Tiny caterpillars can enter developing pods and damage seed or devour the entire contents of the pod.
Narrow-leafed lupin pods and seeds are not usually damaged by native budworm until they are close to maturity and the pods are losing their green colouration, although there has been one report this year of budworm caterpillars damaging young lupin pods.
Canola is similar to narrow-leafed lupin in that pods only become attractive to caterpillars as the crop nears maturity and begins to hay-off. Caterpillars of all sizes will enter pods at this stage, with larger caterpillars doing the most damage.
Native budworm moth trapping surveillance
- Usual automated and manual trapping locations
Budworm moth numbers reported by volunteer farmers, agronomists and DPIRD staff have again remained low for most of WA’s wheatbelt over the past week. The higher numbers reported this week include: Merredin (45 moths), Southern Cross (23), Mount Ridley (20), Doodlakine (14), Dowerin (9), Kellerberrin (9) and Kirwan (7).
A mapped view of the native budworm trap captures is available at cesar’s MothTrapVisWA page. For recent native budworm field reports refer to DPIRD’s PestFax map.
The economic spray threshold levels will vary with crop type, grain price and control cost; these can be calculated for each grower’s particular situation using a simple formula outlined in DPIRD’s Management and economic thresholds for Native Budworm page.
More information on native budworm can be found at DPIRD’s;
- 2020 PestFax Issue 7 article Native budworm and other moths are active
- PestFax Issue 10 article Native budworm update. Caterpillars are being found in cereals
- PestFax Issue 13 article Native budworm caterpillars are damaging cereal crops.
For more information contact Alan Lord, Technical Officer, South Perth +61 (0)8 9368 3758 or +61 (0)409 689 468.
Article author: Alan Lord (DPIRD South Perth).
Powdery mildew in wheat
- Esperance region
James Bee (Elders) has recently reported finding powdery mildew on Scepter wheat near Mailalup. The crop was at the booting growth stage.
Quenten Knight (Agronomy Focus) has found low levels of powdery mildew in Scepter wheat near Neridup. The crop was at stem elongation. The wheat was spader seeded with no in-furrow fungicide applied at seeding. The crop was going to be sprayed with a foliar fungicide.
Quenten has also reported finding moderate to severe infection of wheat powdery mildew in a booting Scepter wheat near Beaumont. He observed that the infection was worse on lighter textured sandy soils with low potassium levels. The crop hadn’t received any foliar or in furrow fungicide when the report was made.
Plant pathologist Andrea Hills (DPIRD) reports that powdery mildew is starting to generally appear in Scepter wheat crops in the Esperance region and growers are applying fungicide to manage it.
Powdery mildew has distinctive symptoms. Fluffy, white powdery growths (becoming cream-grey with age) of fungal spores can be seen on leaf surfaces and stems. Under severe pressure later in the season, mildew can move into the heads.
It is crucial to control powdery mildew in wheat before it becomes too severe and develops in the upper canopy and on heads, as then it is very difficult to control. A registered foliar fungicide can reduce the disease impact, but growers need to consider the weather outlook, variety susceptibility, growth stage and crop yield potential when deciding whether an economic response to fungicide application is likely. Flutriafol at sowing (Hiload, Impact, Jubilee etc) is very effective in preventing early build up in risk prone environments where Scepter is grown.
The wheat variety Scepter is susceptible to very susceptible (SVS) to powdery mildew. For more variety disease ratings refer to the department's 2020 WA Crop Sowing Guide - Wheat.
If wheat powdery mildew is present and increasing in the canopy and the weather outlook is favorable (humid and mild), it is recommended that growers intervene with a well-timed application of registered foliar fungicide in susceptible varieties to stop disease reaching damaging levels and moving onto the flag leaf and head. For more information refer to the department’s Registered foliar fungicides for cereals in Western Australia page.
Managing fungicide resistance
If you suspect fungicide resistance in your paddock then researchers at the Centre for Crop and Disease Management (CCDM) would love to hear from you. To get in touch please email firstname.lastname@example.org or email@example.com . Alternatively, in Esperance Port Zone, sampling for resistance can be arranged with Andrea Hills (048 575 091) or King Yin Lui (0472 848 519).
For more information on diagnosing and managing this disease refer to DPIRD’s Managing powdery mildew in wheat page.
To read about previous powdery mildew this season refer to the 2020 PestFax Issue 10 Barley powdery mildew article.
For more information contact Plant pathologists Kithsiri Jayasena, Albany on +61 (0)8 9892 8477, Geoff Thomas, South Perth on +61 (0)8 9368 3262 or Andrea Hills, Esperance on +61 (0)8 9083 1144 or Ciara Beard, Geraldton on +61 (0)8 9956 8504.
Article authors: Cindy Webster (Narrogin DPIRD) and Andrea Hills (Esperance DPIRD).