Growers chase pest-control answers

Established and transient pests were in the firing line at the 2015 GRDC Grains Research Update for Advisers in Adelaide

Image of two seated men

Greg Baker from SARDI (left) and Paul Umina from cesar presented the pest Q&A at the 2015 GRDC Grains Research Update in Adelaide.

PHOTO: Rebecca Jennings

South Australian Research and Development Institute (SARDI) principal entomologist Greg Baker, and cesar director Dr Paul Umina tackled the tough questions from advisers and growers at the GRDC Update for Advisers in Adelaide and provided tips and tools to reduce the impact of pests on crops.

Q. What challenges do growers and advisers face when it comes to monitoring pests?

Dr Umina: There are many. Migrating species are particularly challenging due to their unpredictability; a paddock that has not had pests for years can suddenly be rife with them. Resident pests can be a little easier to predict by using paddock history, and agronomic and weather data to determine the likely presence (and numbers) of certain pests within a paddock. Changes in farming practices, such as retained-stubble systems, are presenting new challenges for growers around monitoring pests at the paddock level.

Q. What new tools are on the horizon to help monitor pests?

Mr Baker: Automated camera systems linked to data loggers to monitor pest activity in real time. For example, in collaboration with Michael Richards from Ag Excellence Alliance, SARDI is linking camera surveillance methods to climatic data to build our understanding of key environment triggers that initiate snail activity and feeding, so growers can optimise the time of baiting treatments. Other tools, such as unmanned aerial vehicles, are also being developed to assess if green vegetation deficit patches exist in an established crop, so a grower or their adviser can ground-truth the affected area to determine the cause and take appropriate action.

Q. What gaps exist in monitoring and identifying pests?

Mr Baker: There is a scarcity of easy monitoring techniques that provide timely information about established pests. Europe and the US have long-term aphid monitoring in place and it would be good to see this adopted in Australia. The Plant Biosecurity Cooperative Research Centre, backed by the GRDC, is addressing this by developing automated traps for monitoring aphids and moth pests. These will be suitable for monitoring broad areas for new pest incursions and seasonal flight activity of existing pests.

Dr Umina: The challenge is how to monitor broad areas of land in the Australian grainbelt in a timely manner. I would love to see monitoring for resistance status in existing populations of pests such as diamondback moth and green peach aphid so growers can make informed management decisions.

Q. What are the challenges of controlling emerging pests in canola, and what are the options?

Dr Umina: Canola is vulnerable to attack from a number of invertebrate pests, particularly at crop establishment. Pests such as earwigs, millipedes and slaters are presenting new challenges, in part because not much is known about them. Insecticide resistance in other species, such as redlegged earth mites and green peach aphids, are also emerging issues.

Mr Baker: With GRDC support, our group has worked on Mandalotus weevils to better understand their biology and improve their management. We now understand that rain events trigger the emergence of adults from soil in mid-autumn. They continue to emerge for six to eight weeks, and control needs to pre-empt egg laying, so a one-off treatment is never totally effective.  

Q. What are some non-chemical strategies to deal with problem pests?

Mr Baker: Effective control begins with understanding what you are dealing with on a paddock-by-paddock basis, as integrated pest management is specific to each pest type and the type of crops grown. Non-chemical control options for snails include action over summer, such as knocking them to the ground so they are exposed to extreme summer heat or strategic burning. Other non-chemical options include modifying crop rotation to reflect paddock pest history. All chemicals should be critically selected, as all have the potential to limit the ability of natural enemies to contribute to pest regulation.

Dr Umina: There are many cultural and biological control options that can suppress pest populations. For example, sowing into standing stubble is known to reduce the likelihood of aphid landings on emerging crop seedlings. Another is controlling the ‘green bridge’ (volunteer canola, wild radish/turnip, marshmallow and other broadleaf weeds), which are known to host viruses and aphids. However, for some pest species we lack a lot of basic information.

Image of a diamond back moth

Diamondback moth

Q. Some growers are seeing ladybirds control diamondback moth populations. How can growers select chemicals that will not impact on natural predators, such as ladybirds?

Mr Baker: The current generation of insecticides are far more selective in terms of non-invertebrate toxicity compared with the older, pyrethroid chemistry. The reality is, in this age of tight gross margins, broad-spectrum insecticides are the first choice for many – that’s the brutal reality. There are definitely ‘softer’ options, but growers need to be willing to use a different economic metric and take a longer-term approach to softer, but often more expensive, control options.

Q. What are good preventive and containment strategies for resident pests?

Dr Umina: Knowing the paddock history is important. This will point towards the likely pest issues and allow growers to implement preventive options. For example, if slugs were an issue in a particular paddock there is a reasonable chance they will be there the next year. Pre-season strategies such as burning or reducing stubble loads over summer and autumn can reduce slug numbers. Planting less susceptible crops (such as cereals instead of canola), and sowing at higher rates might be considered. For slugs, the timing of baiting is important. Baiting at the time of sowing is critical.

Mr Baker: Understanding the influences of crop rotation on pest population build-up is needed. Growers have seen dramatic differences in slug populations between linseed and canola. It appears that including linseed in the crop rotation can be a non-chemical, longer-term management option for slug issues.

Q. What transient pests are on your radar this year?

Mr Baker: All transient pests respond to different seasonal conditions. Diamondback moth is favoured by dry, warm winter conditions and warrants careful monitoring in canola. Native budworm could be more of a problem this season if conditions are favourable in inland Australia, particularly if the area sown to pulses increases.

Q. How can growers and advisers contribute to better pest monitoring and management?

Dr Umina: Balance the economics of post-emergence insecticide sprays against better assessment of pest risk for more informed decision-making. Making the move towards reducing our reliance on broad-spectrum, non-targeted insecticides.

Mr Baker: More robust, timely and precise monitoring of invertebrates. This monitoring can contribute to the regional picture of pest threats through reporting to the PestFacts service.

More information:

Dr Paul Umina, cesar,

pumina@unimelb.edu.au;

Greg Baker, SARDI,
greg.baker@sa.gov.au;

GRDC Ute Guide – insects

cesar PestFacts

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