Seeing chewing damage in sprayed canola crops but can’t find the culprit?
- Bluff Point
- Tarin Rock
- Amelup
The PestFacts WA team are receiving reports of germinating canola crops across the grainbelt having chewing damage but growers are having difficulty finding the culprit pests to make an identification.
Growers need to bear in mind that applying an insecticide with the knockdown, and even applying a follow up insecticide post sowing pre-emergence (PSPE) bare earth, does not ensure total pest control.
The main reasons for this are usually:
- Pests such as redlegged earth mites (RLEM) and lucerne flea hatch from eggs in autumn and these eggs are not killed by insecticide sprays. If this occurs late, relative to PSPE spray application, then these pests hatch when plants have little to no protection. A post emergent spray may be required, but identification of the pest species is important as effective insecticides and rates differ.
- Where PSPE sprays effectively protect seedlings from ground dwelling pests such as mites and lucerne flea, the germinated plants have no insecticide coverage and are susceptible to flying pests such as moths. Moths can fly in at night out of sight, lay eggs, and emerging small caterpillars then begin to damage seedlings.
- Some pests such as weevils, European earwigs and snails can be very difficult to kill with insecticides and require a specific approach.
- Insecticide resistance in pests such as RLEM and Green peach aphids is well known. If you experience a spray failure and suspect resistance, please contact the PestFacts WA team via email or on +61 (0)404 819 534.
Checking emerging crops for insects
So as crops emerge it is important to remember that differences in pest biology, as well as seasonal differences, means that not one tactic or approach will effectively control pest issues in all paddock situations.
The most effective strategy is to inspect crops during the first three to five weeks after sowing. This is key to early detection of pest issues and early intervention, if necessary, to ensure crops get away to a healthy start.
The following tips can be used to identify damaging insect pests in emerging crops:
- Look up and down the seeding rows for missing plants that may have been chewed off at the base or plants with visible chewing damage.
- Look for insects around and under chewed or missing plants. Don't forget to check under the stubble in the inter-rows.
- What type of damage has the plant sustained?
Understanding the preferred feeding methods and mouth parts of insects can help narrow the lists of culprit insects. For example chewing damage above or below ground is the feeding method favoured by caterpillars (such as webworm or cutworm), European earwigs, weevils and other beetles. Though European earwigs usually leave jagged cuts in the leaf which can be confused with slug/snail damage; whereas caterpillars if immature, leave windows in the leaf which can be confused with lucerne flea damage.
Sucking-type damage appears as wilting and yellowing of plants – it’s usually due to aphids and Rutherglen bugs who have piercing and sucking mouthparts. These pests are easily found.
Still can't find a pest?
Mites and lucerne flea can be smaller than you think, especially when just recently hatched so consider using a hand lens when checking crops.
Place a pitfall trap near plants with damage, this is just a plastic cup dug into the ground so the top is flush with the soil surface. Put about 10mL of water into it and come back after 24 hours.
This has been especially useful in detecting the presence of weevils, slaters and European earwigs. European earwigs are one of the few pests that if numbers are high, can damage well established crops especially if they chew through the stem.
However, a single pitfall trap may not be sufficient, look to place at least three to five pitfall traps. A single nights trapping might not be enough-so consider keeping the trap out for longer.
If damage is still occurring, keep in mind it might not be invertebrates, there are many reports of mouse activity in the regions. To view recent mouse activity or make a report refer to Feral Scan’s Mouse Alert.
Have you found an insect in the paddock that you have not seen before? It could be an incidental or it could be a new pest species. Consider taking the time to get it identified. It is hard to identify an insect from a verbal description. But there are a few things you can do. Have a phone or tablet that takes photos? Take a photo and email it to pestfax@dpird.wa.gov.au . We also encourage taking a photo and attaching it to your report when using the PestFax Reporter app.
For more information on monitoring insects in emerging crops refer to;
- DPIRD’s Monitoring insects and other crop pests page
- GRDC’s Monitoring for insects in canola. Part 1 video
- GRDC’s updated I SPY manual.
For more information contact Research scientist Svetlana Micic, Albany on +61 (0)8 9892 8591.
Article authors: Svetlana Micic (DPIRD Albany) and Dustin Severtson (DPIRD Northam).
Mites and lucerne flea are active
Redlegged earth mites
- Tambellup
- Gnowangerup
- Condingup
Redlegged earth mites (RLEM) have been causing damage to canola crops at Tambellup, Gnowangerup and Condingup.
Many of the reports received of RLEM causing damage in germinating crops have had insecticide applications of synthetic pyrethroids (SP’s) and organophosphates (OP’s). Crops are being closely monitored and RLEM will be tested for insecticide resistance. In the meantime the growers are planning on applying Pegasus® but only if canola cannot outgrow feeding damage.
If you notice RLEM surviving applications of insecticides please contact DPIRD technical officer Alan Lord or DPIRD research scientist Svetlana Micic to discuss and arrange for paddocks to be tested.
Most RLEM are expected to have hatched in the Great Southern region of WA. RLEM typically hatch after rain and 10 days of mean temperatures below 20oC.
For the central and northern agricultural regions hatchings are predicted to have occurred by late May to early June.
A RLEM hatch timing tool is now available. This tool, developed by Cesar Australia with investment from GRDC, helps to aid decision making by predicting when eggs will hatch in autumn, which indicates when to increase crop monitoring. The map above shows predicted RLEM hatchings for WA by the tool at 5 May 2022. Cesar Australia is keen to ground truth its hatching predictions. For more information refer to the 2022 PestFacts south- eastern article Predicting redlegged earth mite hatch dates.
For more information on RLEM refer to the DPIRD Diagnosing redlegged earth mite page.
Bryobia mites
- Gnowangerup
- Esperance region
Jack Batchelor (Nutrien Ag Solutions) has found Bryobia mite causing damage to canola, which was sown after pasture, at Gnowangerup. Post-sowing pre-emergent (PSPE) sprays of bifenthrin at 200mL/ha were applied straight after seeding. It is highly probable the mites hatched post spray application.
Bryobia mite have been found in canola crops across the Esperance area.
Adult bryobia mites are reddish-grey with a pie-shaped body, red legs and two long forelegs. For more information refer to DPIRD’s Diagnosing bryobia mite page.
Balaustium mites
- Esperance
Balaustium mite has also been reported in canola at Esperance.
Balaustium mite causes minor damage to crops that are growing well. This pest tends to retard crop growth in moisture stressed crops. Its only recommended to control this mite if crops are not out-growing damage.
The adult balaustium mite has a brownish / red body, red legs and looks similar in appearance to the redlegged earth mite. If viewed under a magnifying glass or microscope short, stout, velvety hairs can be seen covering the body. The adult balaustium mite grows to almost twice the size of redlegged earth mites. Several generations can occur each year.
Feeding by these mites cause distortion to cotyledons and a silver or white discolouration on leaves. Damage is more severe when seedlings are stressed (for example, cold, waterlogged or very dry conditions). For more information refer to the DPIRD Diagnosing balaustium mite page.
Lucerne flea
- Nyabing
- Borden
- Ongerup
Lucerne flea have hatched this week and caused patchy damage in canola seedlings near Nyabing. They have also been found in pasture paddocks near Borden and Ongerup.
The lucerne flea is a Collembolan or 'springtail'. Adult lucerne flea are approximately 3mm in size and green-yellow in colour.
It is expected that growers who have had lucerne flea issues in the past can expect to have hatchings occurring. Lucerne flea numbers this year will depend on what the population was in spring 2021.
Control of lucerne flea, if crops are not out-growing damage, relies on OP spray applications. Be careful to check the label as some formulations require green plant material to be effective. The PestFacts WA team receives reports each year of spray failures which can be linked to insecticide choice and a lack of green plant material.
For more information about diagnosing and managing lucerne flea, refer to DPIRD's Diagnosing lucerne flea page.
Correct identification and control measures
It is easy to confuse the micro pests such as mites and lucerne flea so growers and consultants are urged to correctly confirm the identity of the pest before making management decisions. Correct identification is critical for applying the correct management option.
Identifications can be made by using the DPIRD MyPestGuide Crops app which includes images and information of mite pests.
Alternatively, you can send images for confirmation through the PestFax Reporter app.
For registered insecticide recommendations for mites and lucerne flea refer to DPIRD’s 2022 Autumn/Winter Insecticide Guide.
For more mite and lucerne flea information contact Research scientist Svetlana Micic, Albany on +61 (0)8 9892 8591 or Technical officer Alan Lord, South Perth on +61 (0)8 9368 3758.
Article author: Svetlana Micic (DPIRD Albany).
Article input: Dustin Severtson (DPIRD Northam), Cindy Webster (DPIRD Narrogin) and Lizzy Lowe (Cesar Australia).
Slaters
- Amelup
Technical officer Rachel Golledge (DPIRD) has found slaters causing extensive damage in a germinating canola near Amelup. The slaters were active in patches of the paddock that had heavy, cloddy soil and ring barking or chewing through 20% of seedlings. The paddock contained many dead slater carcases, indicating the population has been present in the paddock for a while, and had good stubble cover on the ground.
Slaters survive on organic matter on the soil surface. If the organic matter dries out the slaters cannot survive. The heavy stubble load on the reported paddock aided their survival over summer.
Entomologist Svetlana Micic (DPIRD) says that in some years, slaters can be difficult to control.
At crop germination the only option is to bait or to spray. Baits registered for slater control have better efficacy than baits registered only for mollusc control. The application of residual insecticide sprays have had some efficacy in protecting a germinating canola crop from slater damage. However, as slaters are nocturnal and shelter under stubble it can be difficult to get good spray coverage for their control.
For more information refer to DPIRD’s Diagnosing slaters in crops and GRDC’s Mitigating snails, slugs and slaters in Southern Western Australia.
For more information contact Research scientist Svetlana Micic, Albany on +61 (0)8 9892 8591.
Article author: Svetlana Micic (DPIRD Albany).
Meet PestFacts WA team member – Svetlana Micic
This week we are talking about our team’s field entomologist and research scientist Svetlana (aka Svet) Micic.
Svet is based in the Albany DPIRD office and began working for the department in 2003. Her earlier work involved looking at ways to decrease the number of insects harvested in grain from swathed crops. Svet also collaborated with the Australian Plague Locust Commission to create models that predicted locust hatching times.
Over the years Svet, along with other very experienced DPIRD entomologists, has worked on other DPIRD projects to help develop new tools to monitor pests and provide management options. These tools include DPIRD’s MyPestGuide and MyCrop apps.
You will regularly see Svet presenting at GRDC Research Update events, PestFacts WA events and industry field days. Svet also enjoys discussing various invertebrate topics on regional radio - so keep an ear out for her.
Svet’s interest in agriculture comes from her rural upbringing in Arnhem Land in the Australian Northern Territory. This was supported by her parents coming from subsistence farming backgrounds in Europe. After finishing school in the Northern Territory, Svet moved to Queensland to attend university. Svet worked for the NSW Department of Primary Industries before moving to the Albany DPIRD office.
Svet is passionate about making sure that the outcomes from DPIRD research are practical for WA growers.
Article author: Svetlana Micic (DPIRD Albany).
Field pea blackspot disease forecasts for WA are available online
DPIRD’s blackspot in field pea disease forecasts for Western Australia for the 2022 season can now be viewed online. The latest forecast is current to 2 May 2022.
Blackspot becomes established when spores of the fungi produced on old field pea stubble are carried into the new crop by wind after rain events. Infection may occur at any stage of plant growth.
For the majority of locations across WA, the blackspot risk is currently high or medium and DPIRD recommends that growers delay sowing in these areas until the blackspot risk reduces.
Field pea is a crop that does not suffer yield penalties for later sowing in May, so can be left until the end of the seeding program before sowing. For agronomic reasons it is not recommended that field pea is sown in any location in WA before the 10 May.
The blackspot risk is low at Gairdner, Jacup and Mount Barker. For Jacup areas it would be safe to commence sowing field pea after 10 May. For agronomic reasons sowing should be delayed at Gairdner until after the 18 May and at Mount Barker until after the 25 May.
To view the latest forecast, refer to DPIRD's Field pea blackspot management guide for Western Australia - 2 May 2022.
For more information on blackspot, refer to the department’s Diagnosing blackspot in field peas webpage.
Blackspot Manager is a model that predicts the maturity and release of spores using weather data from the nearest weather station. Advice is given on when it is safe to sow field pea.
To subscribe to the free blackspot SMS service, text 'blackspot', your name, and nearest weather station to +61 (0)475 959 932 or email Blackspot.Manager@dpird.wa.gov.au to subscribe to the direct email service.
For more information on blackspot in field peas, or the forecasts, contact Research scientist Jean Galloway, Northam on +61 (0)475 959 932.
Article authors: Jean Galloway (DPIRD Northam) and Cindy Webster (DPIRD Narrogin).
PestFacts WA podcast
We now have a podcast that discusses the PestFacts WA service!
Tune in and listen to DPIRD project lead Cindy Webster talk about how the PestFacts WA team assists the WA grains industry each growing season, how important your reports are, our recent name change and the app upgrades we busy working on behind the scenes.
To listen to this podcast visit the Grower Group Alliance Grains podcast page.
You can now subscribe to DPIRD's Grains Convo series on Apple Podcasts and Spotify.
For more information on this podcast contact Research agronomist Cindy Webster, Narrogin on +61 (0)8 9881 0201.
Article author: Cindy Webster (DPIRD Narrogin).