PestFacts June 2021
New tool for redlegged earth mite hatch framing
A new tool has been developed by Cesar Australia to predict when the conditions for possible Redlegged earth mite () (RLEM, Halotydeus destructor) hatching in autumn are met. This prediction, and knowing RLEM biology, can help inform a more tailored monitoring program.
Why timing is important
Year-round integrated management is the most efficient way to manage RLEM long term, especially as insecticide resistance within populations is becoming more common. The GRDC RLEM Best Practice Management Guide is available to help determine your risk levels and guide you through key actions throughout the season. Now is the critical time for monitoring RLEM during seedling emergence and establishment.
RLEM over-summering eggs in south-eastern Australia will typically hatch after 5 mm of rain over 5 days, followed by 10 days of mean temperatures below 19 degrees Celsius. The new RLEM hatch timing tool uses local weather data to calculate when these conditions will be met and then estimate a possible RLEM hatch date. This date should be used to aid in deciding when to monitor – and always ground-truth models with observations.
While weather conditions help determine the likelihood of RLEM egg hatch, other factors play an important part in whether RLEM will be an issue this year – including your previous management decisions and the paddock risk for this season.
How to use the tool
The RLEM hatch timing tool just requires you to input your location of interest. The tool will then provide the date when mite eggs are predicted to hatch for the current year and the hatching probability based on predicted hatch dates across the past 25 years of available data.
For more information on using the new tool, view the Cesar Australia RLEM decision tools webinar.
We need your reports
To improve the usefulness and accuracy of the hatch timing tool, Cesar Australia needs further validation of the estimates provided by the model. Reports from growers and advisors are an extremely valuable part of this validation. If you have checked for mites this season, please consider providing Cesar Australia with your report via the online form. It only takes a minute.
If you have any feedback about possible future features, please contact the PestFacts south-eastern team by sending an email to pestfacts@cesaraustralia.com
Acknowledgements
Many thanks to Dr James Maino for the development of the tool, Dr Garry McDonald, Dr Paul Umina and Professor Ary Hoffmann for the development of the model, Dr Paul Umina and Dr Jess Lye for help developing the article and Leo McGrane for the webinar video.
This web tool was developed by Dr James Maino through a GRDC investment (CES2010-001RXT) with contributions from CSIRO, Cesar Australia, the University of Melbourne, and the Department of Primary Industries and Regional Development.
The original article NEW Redlegged earth mite hatch timing tool is from PestFacts south-eastern, written by Dr Lizzy Lowe. Modified for relevance to South Australia.
Photos:
https://www.pir.sa.gov.au/__data/assets/image/0009/323982/varieties/preview.jpg Redlegged earth mites (C. Svilans)
Slugs hatching in some areas
When you see feeding symptoms on your emerging crops are you sure you know the true culprit? The evidence is often clear: plants going missing, leaves are nibbled on or show silvery patches. However, knowing which pest is causing these issues can be difficult as many pests are active during the night and hide during the day. It is easy to blame the first critter you see…but is that slater really the culprit or might there be others?
A new SAGIT funded research project called ‘CAUGHT RED HANDED’ is trying to clarify these culprits using night-vision (infrared) time lapse cameras. In three South Australian paddocks, we have installed modified cameras focused on small plantings of seedlings (wheat, barley, faba bean, canola, vetch and lentils) replaced fortnightly. The images below were taken at Riverton at the end of April and you can clearly see earwigs munching into cereal seedlings causing lopping and even eating beans before they fully emerge. The paddock is bare and would appear to be lifeless but at night it comes alive with earwigs, weevils, millipedes, beetles and other invertebrates.
Initial test runs pre-sowing have shown an amazingly high variety of organisms, and we also regularly observed vertebrate pests (such as mice) enjoying an evening snack in an otherwise bare paddock. Between the mice and the earwigs, the seedlings were completely gone within three days, however, that was when the seedlings were the only sprigs of juicy green present this autumn. Currently, we are now collecting data from these cameras while the crops are emerging.
In addition to the camera monitoring, pitfall traps are also deployed to help us understand invertebrate movement from edges into crops. Understanding the conditions that cause some resident (generally harmless) invertebrates to switch to eating crop plants will help to predict risk.
We will soon review the latest footage taken after field sowing at the three sites in Riverton, Rhynie and Finniss and will keep you informed of our observations.
For more details, contact:
Maarten van Helden
Phone: 0481 544 429
Email: maarten.vanhelden@sa.gov.au
Weevils spotted in canola
Several species of adult weevil have been spotted in cotyledon canola in recent weeks. Adult Mandalotus weevils (Mandalotus sp.) have been reported at Mt Hope and Warooka. A mixed population of adult vegetable weevil (Listoderes difficili) and spotted vegetable or desiantha weevil (Steriphus diversipes) was reported near Meningie.
Identifying weevils
The distinguishing feature of all adult weevils is the extended snout on the head. There are numerous species of weevils found in cropping paddocks, so refer to these resources with comparisons to tell them apart:
- GRDC Back pocket guide: Crop Weevils
- ISPY Manual – in section 4, page 29 for a comparison of common weevils.
PestFacts SA subscribers can also send specimens in for free identification. For more information, refer to the sending specimen guide.
How to report
The PestFacts SA team always wants to know what invertebrates you are finding in your crops and pastures, whether it is the ‘usual’ pests, beneficial or unknown. To make a report, please contact:
Rebecca Hamdorf
Phone: 0429 547 413
Email: rebecca.hamdorf@sa.gov.au
Maarten van Helden
Phone: 0481 544 429
Email: maarten.vanhelden@sa.gov.au
Source of reports: Nigel Myers (Nutrien Tumby Bay), Michael Nash, Matt Howell and Georgia Cole (Platinum Ag Coorong).
