The 2025 Grains Research and Development Corporation (GRDC) Grains Research Updates showcased the latest research and results from across the grains industry.
Several Crop Protection researchers from the Western Australia (WA) Department of Primary Industries and Regional Development (DPIRD) were among the industry experts presenting on a variety of topical issues at the Perth and regional Research Update events.
In this issue of Protecting WA Crops, we spotlight the presentations delivered by Senior Research Scientist and 2025 Seed of Light winner, Svetlana Micic at the Perth event and Senior Research Scientist, Ben Congdon who spoke at the Wagga Wagga update in New South Wales.
Beneficial insects in canola
At a glance:
- Increasing restrictions on pesticide use is driving market demand for alternative pest control methods in canola.
- An integrated pest management strategy involving natural enemies of insect pests could be a promising strategy for pest control.
- We are investigating the factors that impact the arrival timing of natural enemies, their impact on pests and their persistence in the field.
Pest management in canola has always been challenging due to the crop’s high susceptibility to pests. Traditionally, control strategies have relied heavily on non-selective pesticides. However, growers are facing increasing restrictions on pesticide use, whether due to regulatory changes or market demands. As a result, alternative approaches to pest control are becoming necessary.
One promising strategy involves using natural enemy species (e.g. lacewings, ladybeetles, parasitoid wasps, carabid beetles and many other species) to suppress pest populations. However, for natural enemies to be effectively integrated into pest management, robust surveillance systems are needed. These systems must combine diverse monitoring techniques to determine when and where natural enemies are present in canola fields, providing growers with the confidence to rely on them for pest control. A surveillance system that incorporates natural enemies would allow growers to either delay spraying while monitoring population dynamics or opt for selective insecticides that preserve beneficial species.
WA DPIRD is participating in a 5-year project led by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and supported by the GRDC. In partnership with the South Australian Research and Development Institute (SARDI), New South Wales Department of Primary Industries and Regional Development (NSW DPIRD), and Murdoch University, the project is focused on answering 2 key questions:
- Do early-season pesticide applications affect the arrival time of natural enemies, thereby impacting their ability to control late-season pests?
- Does the early arrival of natural enemies in the late season help reduce pest populations and minimize crop losses?
To answer these questions, the team developed a standardised trial protocol to be implemented across multiple locations over several years. They introduced contrasting treatments — some with common insecticide use and others without. This approach enables researchers to observe sites with different levels of pests each year and captures the diversity of natural enemies present in canola crops.
In 2024 (the first year), field trials were conducted across multiple locations, including Northam and Katanning in WA, Wagga Wagga and Tamworth in NSW, and Rosedale in South Australia (SA). The canola cultivar Bonito was used at the WA sites, while 43Y92CL was sown at Tamworth and Rosedale, and Renegade was used at Wagga Wagga. Each site included 2 treatment groups: sprayed and unsprayed. The sprayed treatment involved multiple insecticide applications, including:
- chlorpyrifos (500 gai/L) at 350 mL/ha, applied seven days prior to seeding
- imidacloprid (600 gai/L) at 400 mL/100 kg of seed, applied as a seed dressing
- bifenthrin (250 gai/L) at 820 mL/ha, applied at the time of seeding
- alphacypermethrin (250 gai/L) at 160 mL/ha, applied at the stem elongation stage
These insecticide groups are useful for controlling pest species but are also considered to be very highly toxic or highly toxic to many natural enemy groups in controlled laboratory studies.
Additionally, at the Northam site, cyantraniliprole (100 g/L) was applied once at 150 mL/ha during the flowering stage to target diamondback moth (DBM) larvae that had reached threshold. The unsprayed plots did not receive any insecticide treatments (either via sprays or seed dressings). However, due to significant early damage from redlegged earth mites, the unsprayed treatment at Northam required resowing to establish an adequate crop. Notably, Northam was the only trial site with a pasture rotation in 2023, whereas all other locations had a cereal crop in the previous season. Multiple techniques were used to monitor crops for pests, predators and parasitoids on the ground, in the air and on plants. The data from 2024 has not yet been fully analysed but patterns are described below.
Aphids and their parasitoid wasps
In both sprayed and unsprayed treatments, sticky traps captured parasitoid adults flying either at the same time as their host aphids-coinciding with crop germination (Northam and Rosedale) or after their host (Katanning and Tamworth). At Wagga Wagga, parasitoid wasps were detected 3 weeks later in the sprayed treatment on sticky traps. The sweep net results, which collect samples directly off the plant, showed no difference in the time of arrival of aphid parasitoids between sprayed and unsprayed at 2 locations (Northam, Tamworth), a delay in the sprayed treatment at 2 locations (Katanning and Wagga Wagga) and the opposite pattern at one site (Rosedale).
Although parasitoids were generally present very early in the season in canola fields the insecticide applications appeared to affect their persistence and activity within the crop. Plant assessments detected parasitised aphids (mummies) at least four weeks earlier in the unsprayed treatments compared to the sprayed treatments. Overall, aphid numbers remained low, preventing an assessment of the parasitoids' impact on aphid populations across the season.
Diamondback moth patterns
Arrival of DBM moths was monitored using pheromone traps at 4 locations, but only in WA was DBM a consistent problem for growers in 2024. At Tamworth and Wagga Wagga, the adults arrived at the same time in both treatments, but there were predators present before DBM larvae were seen on the canola plants (based on samples taken with sweep nets). In WA the adults arrived earlier in the crop growth cycle, and earlier in the sprayed treatment in Katanning, and in the unsprayed treatment in Northam. The predators were then detected well after the larvae were found on the plants and there appeared to be a difference between the treatments.
Across all the sites we can see that natural enemies are present very early in the canola growth cycle, and insecticide applications do impact them but in inconsistent ways. Insecticide use may affect their ability to persist within the crop over time, but more analysis is required to understand the different factors that are important in each location.
To learn more about beneficial insects refer to the GRDC Back Pocket Guide Beneficial Insects.
Attribution
Canola Allies: Tailoring Practices for Beneficials in Canola Systems (2023-2028). GRDC Investment CSP2309-004RTX Minimising damage of invertebrate pests in canola through a better understanding of the impact of beneficial insects. A collaborative research project led by CSIRO, in partnership with NSW DPIRD, SARDI, Murdoch University, DPIRD and Biological Services.