For more than a century, sugar beet growers across the Great Lakes region have battled Cercospora leaf spot, a fungal disease that remains one of the industry’s most destructive and costly threats.
The disease, which thrives in warm, humid conditions, attacks sugar beet leaves and reduces the plant’s ability to convert sunlight into sugar. Left unchecked, it can slash yields, diminish sugar content and inflict significant economic losses on growers.
“Circospora leaf spot is one of the most economically damaging foliar pathogens of sugar beets,” said Ryan Humann, a field scientist with Corteva Agriscience.
According to the Beet Sugar Development Foundation, Cercospora leaf spot could have caused more than $900 million in economic losses during the 2024 production year if left unmanaged. Researchers estimate the disease can reduce tonnage and sucrose yields by more than 40 percent, while losses in the Great Lakes region can exceed six tons per acre and reduce sucrose content by three percentage points — translating to more than $700 per acre in lost revenue under current market conditions.
The threat is especially significant in Michigan, where weather conditions often favor disease development.
“Depending on the environment—humidity, moisture, some other factors—it really can blow up, and like, you can have an epidemic. And if you don’t manage that with fungicides or genetic resistance, if it’s left unchecked, it’ll start to rob farmers of their sugar beet yields as well as sugar quality at the end of the year. So, it can be pretty devastating if left unmanaged,” according to Humann.
The challenge facing growers has become increasingly complicated in recent years. Repeated use of existing fungicides has led to resistance issues, reducing the effectiveness of some products. Industry researchers say a relatively new genetic trait designed to improve tolerance to Cercospora leaf spot has also become less effective as the pathogen continues to evolve.
Because the disease is polycyclic — meaning it can produce spores multiple times during a single growing season — growers often must make numerous fungicide applications to maintain control.
This year, however, sugar beet farmers will have access to a new disease-management tool.
Corteva recently announced the launch of Verpixo™ fungicide, following registration by the U.S. Environmental Protection Agency. Available for the 2026 growing season, the product introduces a Fungicide Resistance Action Committee (FRAC) Group 21 mode of action to the U.S. sugar beet market, offering growers a new option for disease control and resistance management.
“Corteva just happened to develop an all-new one that’s never been used in sugar beets or, frankly, in a lot of other crops in the U.S. The active ingredient is florylpicoxamid. And essentially, it’s an all-new mode of action for sugar beets, a FRAC Group 21, which is a quinone inside inhibitor, so QII,” says Humann.
The fungicide, which contains Corteva’s Adavelt™ active ingredient, was classified by the EPA as a reduced-risk chemistry. Developed from a naturally occurring compound found in soil bacteria, it provides broad-spectrum disease control and can be incorporated into integrated pest management programs designed to slow the development of fungicide resistance.
According to Corteva, Verpixo™ offers translaminar activity, allowing it to disrupt fungal germination on both the upper and lower leaf surfaces. The company says the product provides preventive disease control while helping preserve the effectiveness of existing fungicides through rotational use.
Researchers and industry experts say introducing new modes of action is critical as growers work to stay ahead of resistant disease populations.
“So, really, we’re bringing a truly a new tool to the toolbox for growers to use and implement and incorporate into their leaf spot management programs to help give these other fungicides a little bit of a break. So, it’ll be great and should help to prevent resistance development and also manage that, if used appropriately,” says Humann.
The introduction of Verpixo™ comes as sugar beet producers face mounting pressure to protect crop yields and maintain profitability amid rising production costs. Industry leaders say effective management of Cercospora leaf spot will remain essential, particularly in regions where the disease has historically caused severe outbreaks.
For growers, the new fungicide represents not a cure for the disease, but another tool in a continuing fight against a pathogen that has challenged the sugar beet industry for generations.
CLICK HERE to learn more about Verpixo™ Fungicide from Corteva Agriscience.
CLICK BELOW for Michigan Ag Today’s radio news report:
