Canola growers across Australia are facing a growing challenge: the turnip yellows virus (TuYV). This insidious pathogen, spread by the green peach aphid, poses a significant threat to canola crops, with potential yield losses of 10-20%, and up to 50% in severe cases. What makes this issue particularly concerning is the virus's ability to remain dormant, often without obvious symptoms, until it's too late. As the growing season warms up and rainfall increases, conditions become favorable for the aphid and the virus, making monitoring and early action crucial for canola farmers.
In my opinion, the reliance on neonicotinoid seed treatments has been a major disappointment in the fight against TuYV. Recent research reveals that these treatments no longer provide adequate protection against the green peach aphid, which is a devastating development. This means that even crops treated with neonicotinoids are not immune to the virus, highlighting the need for alternative management strategies.
The symptoms of TuYV can be subtle and easily mistaken for nutrient deficiencies or environmental stress. Dr. Ben Congdon, a senior research scientist at the Department of Primary Industries and Regional Development (DPIRD), warns that foliar symptoms like leaf purpling or reddening, starting at the leaf margins of lower leaves, may progress to the entire plant. However, these symptoms can appear weeks or even months after the virus was transmitted, making it challenging to manage effectively.
To combat this issue, DPIRD has contributed to a comprehensive 'Manage Turnip Yellows Virus in Canola' fact sheet, providing valuable information to optimize crop potential. Foliar insecticides are the recommended solution for targeting green peach aphid infestations and controlling TuYV once the crop is sown. However, these insecticides must be applied carefully and only when the crop is in its early stages of development, from emergence to the seven-leaf stage.
Dr. Congdon emphasizes the importance of targeted insecticide applications, stating that pre-emptive spraying is unlikely to be effective, and widespread spraying once the virus is already present will provide no benefit. The key to success lies in vigilant monitoring and a careful approach to management strategies. By removing broadleaf weeds and volunteers near canola paddocks, growers can reduce the aphid population and virus reservoir.
As the growing season progresses, DPIRD's monitoring efforts in the Northam, Geraldton, Albany, and Esperance areas will provide crucial insights into TuYV risk. Growers and advisers are encouraged to share paddock intelligence through the PestFacts WA Service, developed with GRDC investment, and to report green peach aphid observations using the dedicated app. This collaborative approach is essential in staying ahead of this growing problem and ensuring the health and productivity of canola crops across Australia.
In my view, the battle against TuYV is far from over, and the industry must remain vigilant and adaptable. The failure of neonicotinoid seed treatments should serve as a wake-up call, prompting a reevaluation of our approach to crop protection. By embracing innovative management strategies and staying informed about the latest research, canola growers can mitigate the impact of this insidious virus and safeguard their crops for the future.
