Canola farmers in South Australia are facing a formidable challenge as the Turnip Yellow Virus (TuYV) wreaks havoc on their crops. This insidious virus, spread by the Green Peach Aphid, has the potential to decimate entire fields, causing leaves to turn from yellow to purple and ultimately leading to infection in up to 100% of the plants. Dr. Nicole Thompson, a SARDI expert, has been witnessing the devastating impact of TuYV firsthand, with reports of severe outbreaks across the state. The virus thrives in 'green bridges' - perennial weeds, forage brassica, volunteer canola, and new canola crops - and its spread is facilitated by the aphids feeding on infected plants. The situation is further complicated by the fact that TuYV infections can be non-symptomatic, making early detection and diagnosis a daunting task for farmers and agronomists alike.
The webinar, hosted by the GRDC and featuring experts like Dr. Thompson, Steve Marcroft, Maarten van Helden, and Narelle Nancarrow, emphasized the urgency of the situation. Dr. van Helden highlighted the unusual boom in aphids this year, which has led to a rapid spread of the virus. He advised farmers and agronomists to remain vigilant and take proactive measures to prevent further transmission. The use of pesticides like Versys and MainMan has shown some effectiveness, but the timing of their application is critical, and the wet and cold weather may also impact control efforts.
Another concern is the Sclerotinia stem rot, a disease affecting canola crops in Victoria and New South Wales. Dr. Kurt Lindbeck, a pulse and oilseed pathologist, warned against premature use of fungicides, emphasizing the importance of timing. The optimal stage for treatment is 20-30% flowering, which corresponds to 15-20 open flowers off the main stem. This stage is crucial as it triggers significant shedding or senescence of petals, leading to stem infections. Lindbeck recommended using a ground rig with high water rates and finer droplet sizes to ensure good coverage and penetration of the fungicide to the lower leaves and stems.
As the agricultural season progresses, farmers must remain vigilant and take swift action to protect their canola crops from these devastating diseases. The future of their livelihoods and the stability of the agricultural industry depend on their ability to detect and manage these threats effectively.
