Interview Series 1: New Solutions for Control of Asian Soybean Rust in South America

Soybean is one of the most important crops in South America. In Brazil, soybean plays an important role in the economic development. The export of soybean and its processed products is a main source of income of foreign currency in Brazil. The income of many farmers is dependent on the growth of soybean and the yield of soybean. The recent Sino-US trade friction has facilitated a rapid increase in Brazil’s export of soybean to China. In 2017, some 50.93 million tons of soybean imported to China was supplied from Brazil, which accounted for 53.3% of China’s total imports. Compared to soybean in other countries, the soybean of South America is cost effective, with high protein content, while the price appears to be competitive. The favorable situation in exports will stimulate the plantation of more soybean by the farmers of South America. The soybean output of South America this year is expected to hit the second highest record in history, according to the climate condition and satellite remote sensing. 

The Asian soybean rust has been for long a major disease causing damage to soybean in South America. Since the first-time occurrence of Asian soybean rust in Brazil in 2000-2001, its impact on the soybean crop has lasted for nearly 20 years. The Asian soybean rust tends to occur in warm and humid environments, which may damage the crop leaf and kill crops, resulting in a serious loss of yield. 

Rafael Pereira, senior manager for Regulatory Affairs, Development and Innovation at UPL Brazil, told us that the Asian soybean rust, caused by the fungi Phakopsora pachyrhizi, is the most important disease in soybean, the yield loss being from 10% to 90%, dependent on the geographical region where the disease was reported. 

“Rust is spread overall in Latin America, but in Paraguay, Bolivia and Brazil, growers need to pay a lot of attention and use fungicides to manage it. Brazil, the biggest soy producer in Latin America, experiences rust from south to north with the potential to damage the yield significantly high,” said Jean Zonato, director of Fungicides at Bayer in Latin America. 

Luis Demant, Product Manager Fungicides at Ihara, said, “The weather condition was favorable for Asian soybean rust this year in Brazil; however, the severity of the disease increased only in the last part of the season.” 

“This year, the occurrence of Asian soybean rust in Brazil was more recurrent, especially in the south of the country. Due to the excessive rains, the producers faced difficulties in carrying out cultural dealings at the appropriate time. According to Embrapa, there were more than 641 rust occurrences in commercial crops, the number being higher than the last six soybean harvests that had an average of 350 occurrences,” added Helio Cabral Costa, marketing manager of soybean at BASF.

Over the last dozen years, Asian soybean rust has been spreading overall. Farmers have increased the use of fungicides, which has brought about a serious concern over the increasing resistance issue. The increasing resistance may result in a situation where almost no pesticide can be used for the control of diseases. Statistics show that the sale of fungicides in Brazil has tripled that of 10 years ago, while nearly 56% of the fungicide is consumed for application on soybeans. Experts are calling for action by South America to import more new product varieties for the control of diseases, and are considering a soybean rotation practice. 

“Consuming some 66% of the relevant uses of fungicides, placed in a tropical region and led by a natural process of selection, the populations of Asian soybean rust are now less sensitive to fungicides with a single mode of action (affecting only one site in the fungi metabolism). Since 2008, soybean growers are facing an erosion in the efficacy of Demethylation Inhibitors, also called Sterol Biosynthesis Inhibitors. After that, the Quinone Outside Inhibitors in 2014 and the last confirmation by Fungicide Resistance Action Committee (FRAC) was published in 2017 for the Succinate Dehydrogenase Inhibitor,” elaborated Pereira. 

Zonato provided a graphic showing the efficacy of the main mode of actions since Embrapa, and the agrochemical companies started measuring the efficacy of the compounds. Most of them decreased the efficacy, and rust has become more difficult for growers to manage.

Demant deemed the main point in the control of Asian soybean rust the selection of an effective product and using the chemical tools in a program that involve all good agricultural practices, including select cultivar, area, planting time, fertilizing, and soil preparation. 

“There is no doubt that the main measure for this disease control is still done by spraying fungicides; some three to four applications on average are done per soybean cycle in Brazil. The fungicide should be used as soon as the first symptoms are visible or must be preventative (preferable) and have the resistance gene,” said Pereira. 

“The use of an efficient product since the beginning of the soy cycle is one of the most important decisions for growers after the crop implantation. The choice of a wrong fungicide can predispose the crop for higher infestation along the cycle. After the soy rust appears, there aren’t products powerful enough to stop the disease completely; if growers start wrongly, the risk of losses is high,” explained Zonato.

Besides an efficient product, Zonato also believes that crop rotation and a free period of soybean crop to reduce the source of fungi inoculum, adequate germplasm in the region, earlier sowing, and the time of fungicide application are measurements crucial to have success in the fight against diseases. 

Costa emphasized that it is necessary to adopt a strategy of continuous monitoring of the crop, so that the decision-making of the rural producer becomes more assertive.

■ UPL’s Tridium and Triziman
 

UPL brought to Brazil the fungicide multisite concept and the implementation for row crops. 

Tridium is a combination of three fungicides: one with a multisite action effect, Mancozeb belonging to Group M03; Azoxystrobin that interferes with mitochondrial respiration and belongs to Group C3, and Tebuconazole with a systemic effect that acts as a biosynthesis inhibitor of Sterol, which is a constituent of the cellular membrane of fungi and belongs to the G1 Group, according to the international classification by FRAC. Due to its distinct characteristics, it shows a complete fungicidal action in the inhibition of spore germination, penetration and development in leaf tissue and its sporulation. Due to this differentiated action, it is an excellent option in the management of resistance, and it is recommended to be adopted at the beginning of the development of the crop, that is, before the visual appearance of the symptoms and the stages from V8 to R1. 

After the R1 stage (first soybean flower appearance), the farmer has the option to use Triziman that follows the concept of soybean diseases control at a high level and resistance management. 

Triziman brings the highest concentration of Mancozeb and Azoxystrobin per hectare, especially of Ciproconazole, which is one of the most systemic DMIs and selective for the soybean crop. 

UPL has been contributing to the soybean Brazilian growers, offering complete solutions for the Asian soybean rust control and the disease resistance management.

BASF innovates again by offering a solution for soybean with a new active ingredient thatbelongs to the group of morpholines. The fungicide Versatilis® has curative action in the germination and the development phase of the fungus and has reached the market to be used in associationwith the existing fungicides, enhancing the performance of these products in the control of Asian rust and, consequently, helping to manage resistance. 

Versatilis® offers ease and flexibility of application in the different phases of soybean development, also increasing productivity for the crops. In more than 25,000 hectares of research confirmation areas, the use of Versatilis®, in conjunction with other BASF solutions, has resulted in more productivity, increasing it by two sacks of soybeans, compared to the standard areas of farms where the tests were carried out. This harvest that ended the product had a fantastic performance on the Asian rust associated with Multsstio or another fungicide.

Fox Xpro (bixafen + prothioconazole + trifloxystrobin) is the most powerful and complete fungicide in the Brazilian market. In the last years, Fox Xpro was always a highlight during the net trials of Embrapa and Companies. It is possible because the product has a unique combination of three different active ingredients and mode of actions performing against soy rust and other important diseases for the soybean crop system.

Ihara launched two new tools, Fusão EC and Approve WG, to control the Asian soybean rust. Fusão EC is a mixture that was introduced in the Brazilian market; this product is based on metominostrobin, the most systemic strobilurin in Brazil that promotes better levels to control the Asian soybean rust in a scenario where event F129L is dominant. Approve WG, much more than a protector is a unique product in the Brazilian market that promotes the control of Asian soybean rust, white mold and the final cycle disease. For the best results, we recommend it be applied in association with Fusão EC and Approve WG in a program for the management of soybean diseases.

 
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