Sugarbeet farmers are in a fight to save their lunch from a bully named Cercospora leaf spot (CLS).
The fungus has caused more than 30 percent economic loss for sugar cooperatives in southern and west central Minnesota, as well as southeast North Dakota.
Now, a new fungicide product will help control CLS this summer.
Provysol fungicide from BASF received a Section 18 Specific Emergency Exemption for use by the Minn-Dak Farmers Coop, Wahpeton, N.D., and the Southern Minnesota Beet Sugar Cooperative, Renville, Minn.
The Environmental Protection Agency (EPA) issues a Section 18 to allow an emergency exemption for unregistered uses of pesticides.
Growers in these two cooperatives, as well as growers in Michigan Sugar may use Provysol this growing season on or before Sept. 25, 2019. Just over 70 percent of the sugarbeet acres in the U.S. will be eligible to use the new fungicide.
“We contacted BASF and just asked the question, ‘Hey, we know this is out there on the horizon. Is there any chance of us getting it a little bit early?’ Kudos to them, and I mean that sincerely,” said Mike Metzger, vice president, agriculture and research at Minn-Dak Farmers Cooperative.
The sugarbeet industry works with 1 million acres vs. 170 million acres for U.S. corn and soybeans, so Metzger appreciated BASF listening and providing the new product to the smaller market.
CLS feeds on dead tissue. It produces a toxin called cercosporin that kills living green leaf tissue and multiplies rapidly throughout the growing season. Small circular leaf spots expand into lesions and then cause white, brown dead leaves that stay attached to the sugarbeet crown. Without leaf surface area, the sugarbeet can’t convert sunlight into tonnage, sugar concentration or recoverable sucrose. The root also contains impurities that must be removed, adding to the cost of processing.
The fungus overwinters on sugarbeet leaves, weeds and seed. Lambsquarters, amaranth (pigweed), mallow and bindweed may host CLS. Rainy, wet and muddy conditions with temperatures between 75-85 degrees F favor development.
Sugarbeet growers have dealt with CLS for many years, but the fungus rapidly mutates and develops resistance to fungicides and other products. In 2016, CLS developed a mutation that made strobilurin fungicides – like Headline, Priaxor and Gem – totally ineffective.
Provysol is a triazole. It doesn’t represent a new mode of action, but it is considered a different form of a mode of action than is already used. It is expected to remain viable for a long time if used correctly.
BASF expects to have the product commercially registered during the 2019 growing season, and Provysol will be available to use on other crops.
The active ingredient is mefentrifluconazole – a Group 3 fungicide, or what is called the DMI fungicide class.
“This molecule is certainly different than other triazoles currently in the marketplace for sugarbeets. For example, it does have a stronger, intrinsic activity, which we’ve proven not only in the lab, but in the field as well,” said Ken Deibert, BASF technical service representative. “Its fungal pathogen binding capabilities are certainly unique as well.”
Provysol is known for very fast uptake and cuticle-binding with the sugarbeet leaves, he added.
The product will be applied in early July, as sugarbeet agriculturists want to nip CLS in the bud. Only 5 ounces of product per acre, mixed with 10-20 gallons of water applied by ground or 5 gallons of water by air, are needed.
The sugarbeet industry realizes that chemical applications are not enough to control CLS long-term. Sugarbeet agriculturalists know that growers need both fungicides and resistant varieties to improve success.
The industry is trying to rapidly develop sugarbeet varieties with increased resistance to CLS, and every year the varieties are getting a little stronger, said Metzger.
“We’ve adjusted our criteria in which seed has to meet in order to be sold within our cooperative,” said Metzger. “We made it harder for varieties that were very susceptible to Cercospora to make it into the seed portfolio that was available to the growers.”
The heavy-hitting BASF fungicide, Provysol, or Bayer Crop Sciences’ Proline fungicide, are being paired with “minor league” fungicides for increased activity.
Many of the sugarbeet fields could receive five or six applications per field to control CLS. The Minn-Dak Farmers Cooperative has set up the following 2019 fungicide application protocol:
1) (First application) TPTH (Triphenyltin Hydroxide or Tin) and ManKocide (copper hydroxide and mancozeb)
2) (Second application, etc.)Provysol and Copper fungicide
3) TPTH and EBDC (mancozeb)
4) Proline and Copper fungicide
5) TPTH and EBDC
6) Copper fungicide
The fungicide applications are made at 10-12 day spray intervals or tighter if rain or other conditions require it to maintain CLS control.
The Southern Minnesota Beet Sugar Cooperative (SMBSC) was still determining their fungicide protocol as of mid-June.
“We spent a lot of time this winter looking at different adjuvants and those types of things that might benefit us and give us longer-lasting control,” said Brian Ryberg, SMBSC member and owner/operator of Ryberg Farms. “It all depends on weather.”
Ryberg added that his family began raising sugarbeets in the 1960s. They raise about 800 acres of sugarbeets annually, which are in a five-year rotation with other crops.
In addition to the Minn-Dak Farmers Coop, the SMBSC was decimated by CSL in 2018. Despite six to eight applications of fungicide, the sugarbeet fields had very poor CLS control. Ryberg said CLS is the leading problem within the coop and threatens SMBSC’s future.
“We are excited about the release of Provysol as another tool,” Ryberg said. “We’re looking for any and all improvements to control CLS and this seems to be very promising.”
According to an EPA spokesperson: From 2008-2017, EPA issued approximately 125 emergency exemptions per year. The vast majority of authorized emergency exemptions are for agricultural uses.
Each state that is affected by an emergency can apply for an emergency exemption for a specific chemical and use site. Thus, for one emergency that affects several states, there may be several requests for the same chemical that year. For example, in 2017, while approximately 100 emergency exemptions were issued, these involved about 20 distinct chemicals.