A new fungicide that has proven to be highly effective in controlling Asian soybean rust in Brazil and Zimbabwe has been granted a Section 18 emergency exemption for use on soybeans in most soybean-growing states.

Tetraconazole, which will be sold as Domark in the United States, can be used to protect the crop and stop Asian soybean rust once it appears, according to researchers who have worked with the disease. Domark contains the triazole class of chemistry that is currently used on 75 percent of all soybean acres treated in Brazil.

“There are different categories of triazoles,” says Fabiano Victor Siqueri, technical agronomist with Foundation Mato Grosso, a private organization working with farmers in northwest Brazil. “We have found that some give us a higher level of performance than others.”

Siqueri said Domark and another formulation of tetraconazole that is sold in Brazil have both provided excellent control of Asian soybean rust in tests conducted by Foundation Mao Grosso and other organizations.

“All of the companies here know the products and their level of performance,” he said. “They all know they must make sure they make recommendations that will show performance or farmers will let them know about it.”

Siqueri spoke to a group of Valent USA Corp. and farm chemical supply representatives who spent several days in Mato Grosso and Sao Paulo state. Valent sponsored the trip to help its staff and suppliers learn more about Asian soybean rust and the fungicides available to treat the disease.

Valent recently acquired the rights to sell Domark fungicide in the U.S. soybean market from Isagro SpA. The company expects other Section 18 emergency exemptions to be granted for Domark on Asian soybean rust.

“Domark is recognized as the premier fungicide and has a proven track record for superior control of Asian soybean rust,” said Jamie Nielson, Domark product manager who accompanied the group to Brazil. “Its unmatched control serves as a first line of defense to protect soybean investments and minimize yield losses from Asian soybean rust.”

The two tetraconazole formulations have also performed well in tests conducted by researchers in Zimbabwe, according to Monte Miles, a plant pathologist with USDA's Agricultural Research Service.

Prefacing his remarks with the admonition that he was not recommending any products, Miles told persons attending a soybean rust seminar at the Mid-South Farm and Gin Show that certain triazole fungicides provide longer residual and preventive control than others.

Miles has been coordinating tests involving a number of fungicides used to control Asian soybean rust in Paraguay, Zimbabwe and Brazil. He focused on the test in Zimbabwe in his comments at the Gin Show.

“You have to realize that some products can be applied every seven to 10 days and others every 14 to 21 days,” he said. “We're at 20 days between products in this test. The disease started somewhere between the first and second application in these two locations in Zimbabwe.

“All of the products gave us yield protection, so all can be used,” he said. “When you look at the final disease level, you can see all of the products are different. On this end, you can see we had products with no disease in the field. These have high residual and curative properties.”

The products he referred to included Domark and the other tetraconazole formulation used in Brazil and Zimbabwe.

Miles says research in Brazil and Zimbabwe indicates that the first application should be made at or near flowering and that growers should plan on two applications, 14 to 21 days apart.

Valent's recommendations closely follow those: For the first application, apply 5 ounces of Domark at flowering (the R1 stage of development) or when the first symptoms of Asian soybean rust are found in the area. For the second, depending on rust pressure, apply a labeled fungicide by early pod fill (R5.1), at a 14-day to 21-day interval.

To be sure the product reaches mid-canopy, Valent is recommending Domark be applied with TwinJet, flat fan nozzles with 10 to 20 gallons of water per acre with a ground rig and a minimum of 5 gallons with aerial equipment. Applicators should use a nonionic surfactant with the spray.

Domark will come in a 230 ME (micro-emulsion) formulation that is designed specifically to treat Asian soybean rust in the U.S. soybean crop. “The product is quickly absorbed by the soybean leaf and evenly distributed throughout the plant to insure fast-acting, long-lasting control,” says Nielson.

“Domark can provide protection against Asian soybean rust for more than three weeks. Plus, it protects newly-emerging plant growth for 21 days or longer after treatment.”

Domark will be submitted for full Section 3 registration from the Environmental Protection Agency for soybeans in 2005.

In the Mid-South, Domark is now available are Alabama, Arkansas, Louisiana, Mississippi, and Missouri for the control of Asian soybean rust under a Section 18.