The canola industry in on high alert for what could potentially be the worst year for the damaging virus turnip yellows virus (TYV) since 2014.
Near ideal conditions over summer for self-sown canola volunteers to flourish has meant industry figures are calling on growers to make sure they control the volunteers to prevent the spread of the virus.
There has been substantial rainfall across the nation's major canola growing belt over summer, in the early summer across the eastern states and South Australia and then in late summer in Western Australia.
This will provide valuable subsoil moisture for the upcoming crop but also has meant a substantial green bridge of canola volunteers to host the aphids which spread the viruses.
According to Grains Research and Development Corporation (GRDC) and Agriculture Victoria field surveillance the warm and moist conditions over much of summer have also meant aphids have persisted longer than normal, leading to fears of a quick build up when conditions are favourable during the year.
The field work also found high levels of TYV in canola volunteers.
Turnip yellows virus, formerly known as beet western yellows virus) is an aphid-borne virus that causes yield and quality losses in canola.
According to Western Australian Department of Primary Industry data TYV infection can cause up to 50 per cent yield loss if the plant is infected prior to stem elongation, while there are also quality issues in terms of decreasing oil content and increasing erucic acid and glucosinolate levels, both associated with bitter taste in the end product.
The GRDC has said given the conditions it will be prudent for growers to not only try and control canola volunteers prior to seeding but to also use an insecticide seed treatment and potentially an early season insecticide spray to control the aphids.
The pattern is set up similarly to Australia's last big TYV oubreak in 2014.
In that season an abundance of volunteer canola became infested with green peach aphid , which is the main vector for TYV.
The result was significant infection and damage in that year's crop, with the most severe impact on seedlings that had not received an insecticide seed treatment.
The virus can also infect several other broadleaf crops, including chickpeas, lentils, field peas and forage brassicas, while cereal crops may be at risk from other aphid-borne yellow dwarf viruses.
There will be limited options for control of GPA, with the GRDC reporting it had demonstrated resistance to over 70 insecticides including carbamates, organophosphates and synthetic pyrethroids.
They have also exhibited reduced sensitivity to neonicotinoids and this may be impacting the effectiveness of these insecticides under field conditions.
However, neonicotinoid seed treatments are still considered to provide emergent canola protection from green peach aphid and subsequently reduce or slow down TuYV spread.