Caterpillars in cereal crops: armyworm or budworm?
Recently there have been reports of caterpillars being found in cereal crops. Growers and consultants are reminded that although armyworm are common pests of cereals another caterpillar, native budworm, has also been found chewing on wheat plants in recent years and it is important to be able to distinguish between these species.
In 2020 there were numerous reports of native budworm being found in wheat, with most reports coming from the northern agricultural region (see the PestFax map below).
Caterpillar specimens from some of these wheat crops were submitted to DPIRD diagnostic labs for DNA testing. It was confirmed that native budworm, Helicoverpa punctigera, were in fact feeding on wheat. This was surprising as they traditionally prefer pulse and canola crops.
As part of a GRDC project investigating native budworm feeding on wheat crops, DPIRD are surveying focus crops throughout the Geraldton port zone during 2021 and 2022. Pheremone moth traps have been set up to capture native budworm since early June at 16 focus sites in the region. These traps have been monitored by Rachel Mason (Mingenew Irwin Group) and DPIRD staff. Interestingly native budworm moths have been trapped at all sites. The number of moths captured has ranged from low numbers to over 100 in a fortnight for some sites. Fortunately, native budworm caterpillars have only been detected in low numbers (up to one caterpillar per 100 sweeps) at a few sites.
As we head into spring, growers and consultants are encouraged to send reports of suspect budworm in wheat crops to the DPIRD PestFax service for identification and possible follow-up by DPIRD staff to assess caterpillar numbers and levels of damage.
Lesser budworm
In Western Australia, the most common types of caterpillars which damage cereal crops during winter or spring are lesser budworm (Heliothis punctifera) and armyworms (multiple species). Although some corn earworm (Helicoverpa armigera) moths were detected in pheromone traps in 2017, the caterpillars have never been formally confirmed in cereal crops in WA.
Lesser budworm (which is known to attack cereal crops) caterpillars can be distinguished from native budworm caterpillars by comparing the colour of the hairs along their bodies. Lesser budworm caterpillars have white hairs while native budworm have black hairs (see image above).
Pesticide options for controlling caterpillars can be found in DPIRD’s 2021 winter spring insecticide guide.
For more information refer to DPIRD’s Diagnosing armyworm and Management and economic thresholds for native budworm.
For more information contact Research Scientist Dustin Severtson, Northam on +61 (0)8 9690 2160 or Technical Officer Alan Lord, South Perth on +61 (0)8 9368 3758.
Article author: Dustin Severtson (DPIRD Northam).
Locust hatchings have started
- Merredin
- Southern Cross
Australian plague locust (APL) hatchings have started in Merredin and second instar hopers have been reported in Southern Cross.
This supports the modelled hatching dates generated by entomologist Svetlana Micic (DPIRD) in the 2021 PestFax Issue 14 article Australian plague locust: spring hatchings predicted. Refer to the table below for predicted hatching dates for your district.
| Locality | Predicted 2021 dates for hatchings |
|---|---|
| Allanooka | 16 August - 9 September |
| Coorow | 11 August - 7 September |
| Eneabba | 5 August - 18 September |
| Jerramungup | 14 September - 29 September |
| Kalannie | 12 August - 27 August |
| Koorda | 25 August - 8 September |
| Merredin | 31 August - 14 September |
| Moora | 27 August - 12 September |
| Moorine Rock | 27 August - 11 September |
| Mukinbudin | 23 August - 5 September |
| Scaddan | 29 August - 1 September |
| Yuna | 19 August - 2 September |
Please report any APL hatchings to the PestFax team by using DPIRD’s PestFax Reporter app.
More APL information can be found at DPIRD’s:
- 2021 PestFax Issue 14 article Australian plague locust: spring hatchings predicted
- Diagnosing locusts and grasshoppers in crops page
- Australian plague locust: overview page.
To read about previous APL activity this season, refer to DPIRD’s 2021 PestFax Issue 5 article Locusts are still on the move and Issue 1 article Locusts can damage emerging crops.
For more information contact Research scientist Svetlana Micic, Albany on +61 (0)8 9892 8591.
Article author: Svetlana Micic (DPIRD Albany).
Cereal aphid update
Oat aphids
- Northamptom
- Shackleton
- Kumminin
- Yerecoin
- Beverley
- Katanning
- Gairdner
The PestFax team has received numerous reports of oat aphid activity recently.
Oat aphids have been found by Belinda Eastough who recently tweeted that cereal aphids in Devil wheat at Northamptom were starting to exceed spray thresholds.
David Stead (Anasazi Agronomy) reports that oat aphid numbers have ‘exploded’ in barley at Shackleton to south of Kumminin and Beverley to Yerecoin. Oat aphids are also in wheat crops at Yerecoin.
Below threshold numbers of oat aphids have also been found in wheat at Katanning and Gairdner.
Russian wheat aphids
- Newdegate
- Lake King
- Gairdner
- Gibson
Nathan Moyes (Moyes Agri Consulting) has reported finding Russian wheat aphid (RWA) in Planet barley crops at Newdegate, Lake King and Gairdner. These crops did not have a seed dressing treatment.
An Agworld user has recently reported finding RWA in a wheat crop near Gibson.
Managing cereal aphids later in the season
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.
RWA thresholds are dependent on the crop stage, the time until head emergence, predicted yield and cost of spraying. A RWA threshold calculator is available on GRDC’s Russian wheat aphid page.
Barley crops are most at risk from corn and oat aphids due to the possibility of downgrading from malt to feed quality, as aphid feeding damage can cause grain shrivelling. If 50% of tillers have 15 or more aphids then the feeding damage may cause reductions in yields by up to 10% and also reduce grain size. Yield loss is greater in crops that had aphid colonisation from early tillering.
Aphid colonisation of cereal crops at the flowering stage does not lead to yield loss.
Remember that naturally occurring parasitoids and predators such as hoverflies, 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 (for example pirimicarb) on predators. Hoverflies have been reported this week, refer to DPIRD’s 2021 PestFax Issue 16 article Beneficial hoverfly larvae.
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 can be more effective in decreasing aphid populations than chemical control.
For a list of insecticides registered for use on aphids (including RWA) see DPIRD’s 2021 winter spring insecticide guide or refer to the Australian Pesticides and Veterinary Medicines Authority (APVMA) products database for all chemical control options available for RWA in grains crops.
For more information on cereal aphids, and previous activity this season, refer to DPIRD’s:
- Diagnosing cereal aphids page.
- DPIRD’s Diagnosing Russian wheat aphid page.
- 2021 PestFax Issue 10 article Russian wheat aphid update
- 2021 PestFax Issue 8 article A variety of cereal aphids are active
- 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).
Beneficial hoverfly larvae
- Canna
A grower this week found high numbers of hoverfly larvae while sweep netting a wheat crop near Canna. Cereal aphids were present in the crop which are the food source for the predatory maggots.
As aphids increase in numbers as the weather warms in spring, beneficial species can also increase dramatically in numbers.
The hoverfly larva is a small (up to 12mm long) legless maggot that ranges in colour, but is mainly greenish-brown. They have a slug like body that is tapered towards their pointy-head. They can sometimes be incorrectly identified as caterpillars without careful observation.
Hoverfly larvae are beneficial insects as they feed on aphids with a single maggot capable of eating up to 400 aphids in the two-to-three week period before they pupate. The adult hoverfly resembles a bee with black and yellow colouration. They hover over flowers and are commonly seen darting around above flowering canola crops.
The pupal stage of the hoverfly is a smooth, tan coloured, teardrop shaped creature that maybe seen attached to cereal and canola at this time of the year. The pupae are a little larger than a wheat grain (i.e. about 7mm long and 3mm wide).
When spraying, consider spray options that are soft (for example pirimicarb) on predators.
For more information on beneficial insects refer to DPIRD’s Know what beneficials look like in your crop page.
For more information contact Technical Officer Alan Lord, South Perth +61 (0)8 9368 3758 or +61 (0)409 689 468.
Article author: Alan Lord (DPIRD South Perth).
Native budworm moth trapping
- Usual automated and manual trapping locations
Southern Cross once again recorded the largest flight of native budworm moths this week with 263 moths captured. Larger flights are beginning to move into other areas of the wheatbelt, the higher captures this week include: Grass Patch North (109 moths), Kellerberrin North (89), Badgingarra (57), Maya (42), Dowerin (41), Kirwan (36), Esperance (55) and Doodlakine (25).
All results of this week's manual trappings are available at the department’s Native budworm moth numbers 2021.
A grower has also reported finding nine native budworm caterpillars in 10 sweeps in a lupin crop near Yuna.
Growers and consultants are reminded to be on the lookout for budworm caterpillars in pulse and canola crops in the coming weeks given the increased moth activity detected in some regions. The warmer weather and associated easterly airflows predicted for early next week are likely to encourage further moth flights.
Summary of native budworm moth movements this season
As part of the national iMapPESTS project, the department has expanded its native budworm trapping network to give better spatial awareness of moths as they enter and move through the Grainbelt. A mapped view of the native budworm trap captures is available at Cesar Australia’s MothTrapVisWA page. Viewers need to select the desired trapping date range.
The maps clearly show some native budworm moths entering the northern grainbelt shires in June and then moving down the eastern boundary, all the way to Esperance, in July and August. There has been little movement of native budworm moths into the southwest of the grainbelt.
Pesticide options for the control of native budworm can be found in DPIRD’s 2021 winter spring insecticide guide.
Detailed information on this pest can be found at the department’s Management and economic thresholds for native budworm.
For more information contact Technical Officer Alan Lord, South Perth +61 (0)8 9368 3758 or +61 (0)409 689 468.
Article authors: Alan Lord (DPIRD South Perth) and Christiaan Valentine (DPIRD Northam).
Check susceptible oat crops for leaf and stem rusts
- Geraldton
- Lakes district
- Grass Patch
- Esperance port zone
Plant pathologist Ciara Beard (DPIRD) reports finding leaf rust in wild oats and oat regrowth in the Geraldton district.
Trent Butcher (ConsultAg) has reported that he is starting to find stem rust in Wandering and Carrolup oats around the Lakes districts. Leaf rust is also present in Williams oats but is not aggressively spreading. Crops are at flag leaf to 50% heading and growers are looking to spray paddocks now.
Plant pathologist Andrea Hills (DPIRD) reports that leaf rust is on wild oats throughout the Esperance port zone. Stem rust has also been reported in wild oats at Grass Patch.
Monitoring of oat crops for rust at this time of year is important, especially for susceptible varieties that have not received any fungicide application. While many varieties have some resistance to common leaf rust pathotypes in WA, resistance to stem rust is poorer in many varieties.
Rust spores can be spread long distances by wind and with rust infection in wild oats being widespread this season the disease risk is significant in many regions. Stem rust thrives in warmer conditions than leaf rust and is usually detected later in the season (mid-spring) so continued monitoring of susceptible varieties is recommended into early grain fill.
When monitoring for stem rust look for large, elongated pustules full of dark reddish-brown powdery spores on stems and leaf sheaths, leaves (both sides) and sometimes on heads. The leaf surface at the edge of a stem rust pustule is often ruptured with a tattered edge.
Managing rusts in oats
Leaf and stem rust can cause significant yield and quality downgrades in both grain and hay production systems, particularly in susceptible varieties. For both leaf and stem rust, multiplication and spread of infection is extremely rapid in susceptible and very susceptible varieties and an immediate application of a registered fungicide is recommended for crops at flag leaf and booting.
To check your oat crops variety susceptibility rating refer to DPIRD’s 2021 WA Crop Sowing Guide.
For a list of registered fungicides to use as foliar sprays on cereal crops visit DPIRD’s Registered foliar fungicides for cereals in Western Australia page. Check and observe fungicide labels for withholding periods for export hay cutting.
Samples of rusts can be sent for pathotype testing. Infected leaf samples should be mailed in paper envelopes (do not use plastic wrapping or plastic lined packages) along with your details and collection information (location, variety etc.) directly to The University of Sydney, Australian Rust Survey, Reply Paid 88076, Narellan NSW 2567. Free reply paid envelopes can be ordered from University of Sydney.
For further details see the University of Sydney's Australian Cereal Rust Survey page.
For previous oat rust reports this season refer to DPIRD’s 2021 PestFax Issue 13 article Stem rust in volunteer oats and Issue 10 article Bacterial blight, Septoria avenae blotch and leaf rust are appearing in oats.
For further information on rusts in oats refer to DPIRD’s Diagnosing stem rust in oats and Oats: leaf diseases pages.
For more information contact Plant Pathologists Kylie Chambers, Northam on +61 (0)8 9690 2151, Geoff Thomas, South Perth on +61 (0)8 9368 3982 or Kithsiri Jayasena, Albany on +61 (0)8 9892 8477.
Article authors: Geoff Thomas (DPIRD South Perth), Kithsiri Jayasena (DPIRD Albany) and Cindy Webster (DPIRD Narrogin).
Article input: Kylie Chambers (DPIRD Northam).