American serpentine leafminer detected in WA. Should grain growers be concerned?
- Kununurra
[1]The invasive exotic pest American serpentine leafminer (Liriomyza trifolii) has been found near Kununurra.
This is the first time this species of leafminer has been found on the Australian mainland. It is native to the Caribbean and south eastern United States and is found across the world.
DPIRD staff are conducting surveys in host crops in Kununurra, Broome, Carnarvon and Geraldton to determine the spread of this pest. Distribution elsewhere indicates that it could potentially establish in the south-west of WA, including parts of the grainbelt.
The national technical committee, the Consultative Committee on Emergency Plant Pests, has concluded while eradication may not be technically feasible, due to the pest’s biology, current distribution and wide range of host plants, more surveillance and data was required to make a determination.
How to monitor and diagnose American serpentine leafminer
[2]Adult serpentine leaf miners are small black flies with a yellow head and yellow spots on the thorax. Adult flies are 1-2.5mm long. Adult flies are not very active fliers, although can also spread via natural wind dispersal.
[3]Adult females pierce the leaf surface and lay eggs inside. The eggs hatch in 2-5 days and the larvae start to tunnel and feed causing white or grey lines on leaves. The trails get wider as the larvae grow. The larvae eventually leave the plant to pupate in crop debris or the soil.
It is known to feed on more than 400 species from 29 plant families, including most vegetable and legume crops, as well as ornamental plants. Internationally the grains host list for this pest includes: lentils, chickpeas, field peas and some pastures (such as lucerne and clover). The host status of canola and lupins is yet to be confirmed, if you suspect you have American serpentine leafminer or associated feeding damage in these crops please report it.
The fly’s eggs, larvae and pupae can be spread through the movement of plant material, soil, clothing and equipment
Management and chemical permits
Permits are in place that cover the treatment of a number of exotic leafminer fly species, including American serpentine leafminer. More information is available from the Australian Pesticides and Veterinary Medicines Authority website [4].
It is known to develop resistance so insecticide treatments should be used that incorporate resistance management strategies to minimise that risk.
Overseas, management of leafminers, like the American serpentine leafminer, include the use of natural enemies, such as parasitoids that attack larvae. Pesticides that favour beneficial insects should therefore be considered when managing this pest.
Practice good on-farm biosecurity. Localised spread of the pest is most likely to occur on contaminated plant material or equipment.
What should you do if you suspect you have found American serpentine leafminer?
Growers and gardeners are encouraged to monitor plants and to report any tunnelling leaf damage and suspect flies to the department to help demonstrate the absence and presence of the pest.
Please report any suspected American serpentine leafminer observations and damage to the DPIRD Pest and Disease Information Service [5] on +61 (0)8 9368 3080 or submit a report using the MyPestGuide Reporter app [6].
For more information visit DPIRD’s Biosecurity alert: American serpentine leafminer [7] page.
For more information contact Senior biosecurity officer David Cousins [8], South Perth on +61 (0)8 9368 3920.
Article compiled by: Cindy Webster (DPIRD Narrogin).
Article input: David Cousins (DPIRD South Perth) and Helen Spafford (DPIRD Kununurra).
Sclerotinia in lupins
- Northampton
- Chapman Valley
- Geraldton
[9]Plant pathologist Ciara Beard (DPIRD) reports that lupin sclerotinia is developing in flowering Albus lupin crops at Northampton and Chapman Valley with leaf symptoms and early pod infection visible. This is caused by Sclerotinia sclerotiorum, the same pathogen that causes sclerotinia stem rot in canola.
[10]
[11]Sclerotinia is also starting in a DPIRD lupin sclerotinia trial at Woorree, Geraldton. There are leaf symptoms on both narrow-leaf and albus lupin (both are at early podding stage), and also early pod infection and basal (ground level) stem infection in the albus lupin. Lupin plants with basal infection are visibly wilting compared to healthy plants.
[12]Sclerotinia in lupin is a sporadic disease. It is usually only a problem in paddocks that have a history of sclerotinia in canola or lupin and depends a lot on seasonal weather conditions. Often the disease affects only a percentage of the crop where the crop is densest and stays moist longer but this year with widespread wet conditions it could be a significant issue across whole paddocks.
Symptoms
Predominantly lesions occur in the upper half of the main stem or branches and on pods. Basal sclerotinia occurs at ground level on the stem in very wet conditions/seasons. The fungus produces a white cottony-looking growth that girdles the stem, causing the plant parts above the lesion to wilt and die. Infected pods/spikes can be completely covered by this white fungal growth sometimes resulting in abortion of new pods and grain quality impacts. Hard black sclerotia, 2-8 millimetres (mm) in diameter, are produced in the fungal growth or in the cavities of infected stems or pods. Sclerotia can survive in soil for several years and are the source of new infections.
Management
Registered fungicide options for managing the disease in lupin are extremely limited.
DPIRD research to date has found that fungicides applied prior to or at early stages of disease development can be effective for managing disease in the canopy but a yield response is not guaranteed. Trials have shown that fungicide application should be targeted at early pod emergence stage to protect the pods. However, fungicide is unlikely to provide any control of basal (stem base) infection due to the challenge of canopy penetration and the infection often being at and below ground level. Trials conducted over the last 5 years in the Geraldton port zone found that significant disease developed only in years when winter rainfall was average to above average (2016, 2018, 2020), crops were bulky and had good yield potential. Significant sclerotinia infection was predominantly found on the main spike and pods rather than the stems and this explains why a later fungicide timing to protect pods is likely to be appropriate. All fungicide timings applied from 100% flower to early podding on the main stem reduced incidence and severity of main spike sclerotinia infection as well as pod lesions. However, there was only a significant yield response in two out of seven trials/demos conducted in the Geraldton port zone in seasons with wet winters and a soft finish to the season tended to make a yield response more likely.
More research is required but other than yield, benefits from managing the disease in lupin may lie in reducing sclerote production - that is reduced need to grade seed for sclerote contamination and reduced future risk of sclerotinia in future canola/lupin rotations.
Even though it’s not registered in lupin for control of sclerotinia, Tebuconazole+azoxystrobin (eg. Veritas®) is registered in lupin for control of botrytis grey mould at the timing and rate that could be effective on sclerotinia (and anthracnose). It is registered and known to be effective for managing sclerotinia in canola.
Through a new GRDC funded 4-year project, research is currently underway looking at fungicide (timing and products) and agronomic strategies for reducing the impact of sclerotinia in lupin. As part of this project, DPIRD together with CCDM, and Mingenew Irwin Group are conducting experiments and surveillance in the Geraldton and Albany port zones. To assist with the project investigating disease incidence, please report significant finds of sclerotinia in lupin to the PestFax team [13] or DPIRD Plant pathologists Geoff Thomas [14] or Ciara Beard [15].
A list of registered fungicides and rates for lupin sclerotinia can be found at DPIRD’s Registered foliar fungicides for lupin in Western Australia [16] page. It is important to follow label recommendations and observe withholding periods.
For more information on sclerotinia stem rot in lupins refer to DPIRD’s Lupin foliar diseases: diagnosis and management [17].
The PestFax team have received quite a few reports of sclerotinia (disease on plants and apothecia) in canola crops to date this season. For more information on this activity refer to DPIRD’s 2021 PestFax Issue 11 article Sclerotinia stem rot in canola [18] and Issue 9 article Sclerotinia update [19].
For more information on sclerotinia in lupins contact DPIRD Plant pathologists Ciara Beard [20], Geraldton on +61 (0)8 9956 8504 or Geoff Thomas [21], South Perth on +61 (0)8 9368 3262
Article author: Ciara Beard (DPIRD Geraldton).
Article input: Geoff Thomas (DPIRD South Perth).
Turnip yellows virus detected in canola crops across the grainbelt
- Kwinana west port zone
- Albany port zone
[22]Turnip yellows virus (TuYV) has been detected in canola crops predominantly within the Kwinana west and Albany port zones. High incidences of TuYV infection and typical foliar symptoms have been identified in crops around Meckering, moderate levels around Cranbrook and South Stirlings and low levels at Toodyay and Narrogin. Several crops tested in the Esperance region and around Geraldton and Northampton had little or no TuYV detected in them.
[23]The green peach aphid (GPA), which is the vector for TuYV, has been found colonising canola crops all across the grainbelt (see map below). They were caught on yellow sticky traps in some areas as early as April in the Kwinana west and Albany port zones. They are usually found colonising canola crops at some point in most growing seasons.
[24]Cabbage aphids have also been frequently found colonising wild radish and canola in the grainbelt throughout the growing season and could pose a feeding damage risk to flowering canola crops as temperatures begin to increase.
If GPA are colonising the crop, even at very low numbers per plant, and disease symptoms are present, growers should consider having their crop tested for TuYV through the Department’s Diagnostic Laboratory Services – Pathology Services [25].
Widespread TuYV infection that occurs prior to flowering is most likely to cause significant seed yield and quality losses. Infection after this point is unlikely to cause damage. TuYV symptoms are often mistaken for stress from nutrient deficiency or water logging, however virus infection is likely to interact with these other stresses.
Preventing Turnip yellows virus crop infection
TuYV cannot be sprayed out post-infection so its management primarily relies on the use of integrated disease management tactics deployed at sowing time (See table below). Systemic insecticide applied proactively (but non-prophylactically) during the vegetative growth stage following risk warning will control aphid populations in the crop and may help reduce TuYV spread. For insecticide recommendations, refer to DPIRD’s 2021 winter spring insecticide guide [26].
| Strategy | When | Effect |
|---|---|---|
| Controllilng background weeds | >2 weeks pre-sowing | Reduces local aphid and virus reservoirs |
| Seed treatment | Pre-sowing | Protects seedlings from aphids and reduces virus spread early in crop |
| Sowing into stubble | Sowing | Reduces aphid landing rates and virus spread |
| Targeting high plant density | Sowing | Reduces aphid landing rates and rate of spread |
| Delay sowing | Sowing | Avoids exposing seedlings to peak aphid flights |
| Foliar systemic insecticide | Before aphids are widespread | Reduces aphid populations, may slow down virus spread if used appropriately |
For previous aphid and TuYV findings, and management information, refer to DPIRD’s:
- 2021 PestFax Issue 11 article Green peach aphid and virus update [27]
- 2021 PestFax Issue 5 article Aphid and turnip yellows virus update [28]
- Turnip yellows virus in canola: diagnosis and management [29] page
- Turnip yellows virus early warning system [30] page
- Aphid management in canola crops [31] page.
For further information on GPA, or other aphids, contact Research scientist, Svetlana Micic [32], Albany on +61 (0)8 9892 8591.
For further information regarding TuYV contact Research scientist Benjamin Congdon [33], South Perth on +61 (0)8 9368 3499.
Article author: Benjamin Congdon (DPIRD South Perth).
YellowSpotWM webinar recording can be viewed online
[34]
On Thursday, 15 July 2021 DPIRD research scientists Anna Hepworth and Geoff Thomas presented a webinar about DPIRD’s new YellowSpotWM decision support tool and the wheat disease yellow leaf spot.
If you weren’t able to attend this webinar, or wish the view it again, the webinar recording is now available for viewing on the DPIRD YouTube channel [35].
For more information on these topics refer to DPIRD’s YellowSpotWM – Yellow leaf spot management [36] and Diagnosing yellow spot of wheat [37] pages.
The YellowSpotWM decision support tool works on phones and tablets. It can be download from the Apple app store or from the Google Play store.
For more information contact research scientists Anna Hepworth [38] (modelling tools) on +61 (0)8 9368 3735 or Geoff Thomas [21] (wheat diseases) on +61(0)8 9368 3262.
Article author: Cindy Webster (DPIRD Narrogin).
Redlegged earth mite survey
Are you a grower or advisor in Australia who has encountered the redlegged earth mite?
Cesar Australia is interested in hearing from you!
Cesar Australia is conducting a national survey on redlegged earth mite. Your answers will help to increase understanding of current control strategies and to improve how the redlegged earth mite is managed across Australia. It only takes 10 min!
To thank you for your time, all survey participants will be given early access to module 1 of Cesar Australia’s redlegged earth mite online training which covers identification, distribution, host range and damage.
The survey is being led by Cesar Australia as part of a GRDC investment (CES2010-001RTX), which has been extended to red meat producers through co-investment from MLA and to pasture seed producers through co-investment from AgriFutures. The wider project involves contributions from the Department of Primary Industries and Regional Development (DPIRD), the University of Melbourne, and CSIRO.
If you have any questions, please contact Senior extension scientist Dr Lizzy Lowe [39] from Cesar Australia on +61 (0)3 9349 4723 or +61 (0)484 310 697.
To complete the survey, click here [40]
Article author: Dr Lizzy Lowe (Cesar Australia).