ENTOMOLOGISTS and agronomists are warning brassica producers to be aware of the threat of green peach aphid and associated viruses this season.
Researchers at pest monitoring service Cesar Australia Marielle Babineau and Lizzy Lowe wrote in April that the green bridge of volunteer plants was high in many areas due to the wetter than average summer.
This means there is a higher likelihood of large numbers of aphids in emerging crops through autumn and winter.
Green Peach Aphid (GPA) is particularly problematic as it can spread many viruses, including turnip yellows virus (TYV), formerly known as beets western yellow virus.
The bad news for growers is that Dr Lowe and Dr Babineau identified seasonal conditions this year, with an early autumn break, as similar to those in 2014.
There are also a substantial amount of canola volunteers across the country due to the big plant of the oilseed last year and the wet summer.
Even in areas without a big green bridge farmers are being warned to closely monitor paddocks.
"We haven't had a wet summer but I am noticing green peach aphid on other brassica species, mainly just in the vegetable patch," said Ground Up Agronomy's Michelle Bammann.
"They are a nasty pest so we are really going to monitor closely to ensure they aren't present in damaging numbers," Ms Bammann said.
While GPA is mainly associated with issues in brassicas it can live on a host of other broadleaf species as well, meaning even if farmers did not have canola last year they still need to remain vigilant.
Further compounding the potential problem since the last major outbreak researchers have found some pockets of increased GPA resistance to popular insecticides, such as sulfoxaflor which is the active ingredient in Transform insecticide.
The Pest Facts team reported there were already accounts of significant numbers of aphids present in paddocks in central NSW and Victoria.
They said the timing of the onset of cold conditions was critical to aphid numbers at key crop development stages, as the sharp drop in temperatures experienced in late autumn reduces aphid numbers.
If the current mild weather continues, however, aphids will be a major issue upon crop germination.
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