Cereal crops should be monitored for Russian Wheat Aphid (RWA), as temperatures reach the ideal range for reproduction. Any decision to treat infected paddocks should be based on an economic threshold, plus consideration of the yield potential of the crop and effects on beneficial insects.
RWA have been observed in the western Riverina in recent weeks, however observations have not yet been made outside of areas where RWA were found in 2016. Monitoring should focus initially on plant symptoms, which are much easier to find than the aphids themselves.
The GRDC has recently released a document titled “Russian Wheat Aphid: Tactics for Future Control”, which summarises the most up to date information for what is an evolving issue. Following are key points from this resource:
- Wet conditions in 2016 are suspected to have significantly impacted RWA populations, through direct displacement plus fungal disease. Population dynamics may be considerably different in 2017.
- 18 – 21°C is considered ideal for RWA reproduction.
- Plant symptoms are likely to be the first indication of infestations. These are yellowing, leaf rolling and stripes along leaves.
- Stressed plants are likely to be targeted first, so monitoring should start around gateways, headlands and tree lines.
- An economic threshold of 10% infested tillers once crops reach stem elongation, is the current recommendation for treatment.
- Under dry conditions, the yield potential of the infested crop must be assessed against the cost of treatment.
- The recommended treatment is Pirimor at 125 – 250 g/ha ($4.25 – $8.50 /ha) to reduce the impact on beneficial insects, as these are expected to play an important role in managing RWA populations.
- Removing alternative host plants such as volunteer cereals and summer grass weeds, will be important for management of RWA into the future.
For more information, the full resource is available at: