Keep an eye out for aphid threat
Researchers are encouraging graingrowers across the region to continue monitoring crops for Russian wheat aphid, RWA.
But they suggest only consider treatment if infestations were approaching potentially damaging levels.
Colder conditions since March – in comparison with 2019 – are likely to have slowed aphid population growth during establishment and early tillering stages.
Jessica Lye from research organisation cesar said this was fortunate, because RWA growth rates were also influenced by plant growth stage, with younger plants supporting faster aphid reproduction than older plants.
“If there is wet weather during late winter and spring, as predicted by the Bureau of Meteorology, this is also likely to suppress RWA,” she said.
But she added that despite this outlook, monitoring and making threshold-based decisions remained key to effective long-term management of this aphid.
“Growers and agronomists are advised to monitor for RWA during tillering and stem elongation, keeping in mind current recommended thresholds if they observe any infestations,” Dr Lye said.
Australian intervention thresholds are based on overseas advice, which recommends a spray application when more than 20 percent of all seedlings are infested with aphids up to growth stage 30 and more than 10 percent of tillers are infested with aphids from growth stage 30.
Through Grains Research and Development Corporation investments, led by the South Australian Research and Development Institute and cesar, work is developing a biological and ecological profile of RWA to provide grain growers with scientifically robust management tactics for the future.
This includes economic thresholds for Australian farming systems.