The battle against Sclerotinia: Unveiling the hidden threat to our crops
Sclerotinia, a soil-borne fungal disease, is a silent menace lurking beneath the surface of our fields, ready to strike at the heart of our crops. As more canola and pulses are grown, this disease is becoming an increasingly prevalent concern, with its impacts on yields and grain weight being the focus of a new study. This research, funded by the GRDC and Agriculture Victoria, is shedding light on the causes, effects, and management strategies of Sclerotinia, offering a glimmer of hope in the fight against this insidious pathogen.
The Impact of Sclerotinia: A Devastating Blow to Canola
The study, conducted at the Horsham SmartFarm, has revealed a dramatic reduction in grain weight in mature canola plants infected with Sclerotinia. In conditions simulating 100% humidity, disease-free canola seed weighed 1.3 g, while seed from plants infected with sclerotium-infested soil had a grain weight reduction of 73% to just 0.3 g. This is a stark reminder of the devastating impact of Sclerotinia on our crops, and the need for effective management strategies.
Understanding Sclerotinia: A Durable and Opportunistic Fungal Disease
Sclerotinia is an extremely unpredictable, durable, and opportunistic fungal disease. It can lay dormant in the soil for several years as sclerotia, survival structures made up of hard, compact masses of fungal tissue that germinate in favourable wetter conditions. This makes it a persistent and insidious threat to our crops, as it can strike at any time and from any direction.
The disease can infect crops via two pathways: the soil, through myceliogenic germination, impacting largely the roots, crown, and basal stems; or the air via carpogenic germination, producing ascospores that can be carried on wind and rain affecting the upper canopy. This dual mode of infection makes Sclerotinia a particularly challenging pathogen to manage.
The Importance of Understanding Sclerotinia's Impact
Understanding Sclerotinia's impact on yield is crucial for developing effective management strategies. The study has shown that infection severity varies in regions with similar climates, highlighting the need for a nuanced approach to disease management. By understanding the conditions that support Sclerotinia infection and its impact on yield, we can develop integrated disease management approaches, including seed treatments, in-season fungicides, and rotations, to help growers minimise losses.
The Role of Technology in Understanding Sclerotinia
The glasshouse research at the Horsham SmartFarm has played a pivotal role in understanding Sclerotinia's impact on crops. By simulating a range of conditions, including leaf wetness, drying periods, and relative humidity, the researchers have been able to assess the disease's severity and impact on different crops. This high-tech testing has blown the door wide open in what we can assess in high-throughput settings, offering a wealth of insights into the disease's behaviour and impact.
The Importance of Protecting Crops at Early Stages
The study has also highlighted the importance of protecting crops from infection at early stages. In canola, disease was more severe in plants infected at an earlier stage (10% bloom), underlining the need for early intervention. This is particularly important in the case of soil-borne diseases like Sclerotinia, which can be more destructive than foliar infection pathways.
Management Strategies for Sclerotinia
The findings of the study point to some clear management strategies to help reduce the impact of Sclerotinia. For example, it confirmed the importance of protecting crops from infection at early flowering. While fungicide is an effective control measure, it should be just one part of the disease management picture. Cultural practices, such as rotating crops with cereals as a disease break, are also crucial in reducing the number of disease-harbouring sclerotia in the soil.
The Future of Sclerotinia Management
The study has opened up new avenues for research and management strategies. By understanding the basal infection mechanisms in the production of the disease, we can develop ways to eliminate or reduce the load of sclerotia in the soil. This knowledge will be particularly important as more host plants, such as pulses and oilseeds, are introduced into cropping systems. The farming community has been a big driver of this research, as growers targeting poorer-performing areas of paddocks are asking more questions about soil-borne disease.
In conclusion, the battle against Sclerotinia is far from over, but with the insights gained from this study, we are one step closer to developing effective management strategies. By understanding the disease's impact on our crops and the conditions that support its infection, we can work towards minimising losses and protecting our agricultural systems. The future of Sclerotinia management looks bright, with new technologies and insights offering a glimmer of hope in the fight against this insidious pathogen.
