Sugar Producer

FUNGICIDES | By Keith Johnson, FMC Technical Service Manager Laying the Groundwork Early Successful management of Cercospora leaf spot 20 Sugar Producer APRIL 2019 T wo things rang true for many sugarbeet growers in 2018: irregular weather conditions and disease pressure. This was particularly the case for growers in the middle to southern portions of the Red River Valley. Rain came down heavy early on as well as in the later part of the summer, priming the conditions for Cercospora leaf spot (CLS) development. For growers who were affected by CLS during the 2018 season, it was a struggle to stay ahead of the disease due to the warm, wet weather, especially in the southern growing areas. As the rain and muddy fields kept growers on the sidelines, ideal spray intervals for fungicide applications were missed, and the disease was able to gain an advantage on growers and their fungicide programs. CLS is one of those diseases we know has the potential to be impactful each year on sugarbeet yields and sugar content. With the prevalence of the disease and strobilurin-resistant CLS increasing in many areas, we need to take appropriate measures to ensure fungicide programs are up to the challenge of combating this disease. So, what can we do in preparation for the 2019 season to better protect ourselves from CLS? It starts with breaking down your previous seasons' fungicide programs to see what worked and what didn't. Two aspects I'm encouraging growers to pay close attention to are resistance and residual control. Assessing these insights will help growers create stronger programs that set them up for success not only in 2019, but for growing seasons down the road. Mitigating Resistance Development University and extension experts are recommending more and more that fungicide programs targeting CLS include a diverse mix of broad-spectrum fungicides and a rotation of different modes of action for each application in their treatment program. This approach includes always tank-mixing a broad- spectrum fungicide such as mancozeb, copper or TPTH/tin with newer fungicides and triazoles. Tank mixtures of these broad-spectrum fungicides in a set rotation will help preserve the performance of newer chemistries and slow the progression of CLS resistance. I can't stress enough the importance of protecting the efficacy of these valuable fungicide tools. New fungicides take years to develop, and not many of them are being released for sugarbeet use. Boosting Residual Control This far out from summer, we can't accurately predict what July weather is going to look like, but we can at least plan for the potential of rain and other weather-related scenarios. From a disease control perspective, this requires selecting and using fungicides, especially during the first and second sprays, with a strong residual that allow us to endure periods of inability to get in the field. We should aim to use fungicides with at least 10- to 14-day intervals. In addition to the weather factor, growers are looking for ways to minimize input costs and passes through the field. Adequate residual control can play a role in reducing these elements as well. Having the right level of residual control can help bridge the gap between sprays and provide the disease control needed to protect that crop. From a best practice standpoint, we should aim for two or three fungicide applications in the northern Red River Valley and six or seven in the southern portion, but it is more important for growers to be utilizing the right fungicide chemistry at the right time. Examining New Fungicide Options I mentioned previously that it's not every year a new fungicide is introduced to the sugarbeet market for CLS control. For the 2019 season, however, there is one new fungicide growers should consider for their disease management

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