Researchers see more severe rust in Rio Grande do Sul in the 2017-18 harvest

The low intensity cold recorded in the recently ended winter indicates that Asian rust attacks in the 2017-18 harvest tend to be more severe in crops in Rio Grande do Sul. Experts attest that unlike the last harvest, when low temperatures practically eliminated from planting areas to voluntary soybeans or 'guaxa', reducing the risk of incidence of rust, this year producers must raise awareness regarding the conditions largely favorable to the emergence of the disease.

According to the phytopathology coordinator at the Phytus Institute and doctor in agricultural engineering, Mônica Debortoli, it is possible that the presence of the fungus that causes rust in crops in Rio Grande do Sul will be detected at the beginning of the harvest. The specialist recommends that the producer anticipate the first application of fungicides, preventively, within a period of up to 40 days after planting.

For the researcher and PhD in phytopathology at the Federal University of Santa Maria (UFSM-RS), Ricardo Balardin, one of the main recommendations to the producer is to carry out the correct management of the crop, observing the ideal time for sowing and choosing cultivars appropriate. Shortening the soybean cycle to up to 115 days is another important measure, says Balardin. He also understands that chemical treatment of soybeans must be carried out preventively.

Fungicide program - The treatment of soybeans with the preventive and combined use of the fungicides DuPont Vessarya and DuPont Aproach Prima increased the productivity of the oilseed by up to 4 bags per hectare, according to data obtained in 450 experimental fields from DuPont Crop Protection set up in the 2016-17 harvest.

According to the company's fungicide manager, agronomist Manoel Pedrosa, application of the program resulted in effective control of rust and other soybean diseases, such as target spot and powdery mildew.

The Aproach Prima fungicide, explains the DuPont agronomist, contains the most powerful strobirulin on the market associated with a triazole. The Vessarya fungicide, he adds, results from a mixture of the active ingredients picoxystrobin and benzovindiflupyr.

“Of all the strobirulins on the market, picoxystrobin shows an interesting performance, it is a very efficient product”, says Mônica Debortoli, from the Phytus Institute. According to her, the effectiveness of the fungicide Vessarya has been proven in controlling rust and end-of-cycle diseases. Mônica is part of a group of experts who have been studying the action of carboxamides in soybean management.

Balardin, from UFSM-RS, states that one of Vessarya's differences is the molecule formed by a strobirulin and a carboxamide with a broad control spectrum. “When applied preventively, the product provides a very satisfactory level of control”, points out the researcher. “The Vessarya fungicide is effectively a great alternative for controlling soybean rust in Rio Grande do Sul,” he adds.

“Vessarya’s big difference is the control of Asian rust and other end-of-cycle diseases, because picoxystrobin shows excellent efficiency. If we compare picoxystrobin with other strobirulins we will see that it remains highly efficient. Another novelty of this product is the control power of benzovindiflupyr”, adds Carolina Deuner, researcher at the University of Passo Fundo (UPF).

For the researchers interviewed, the inclusion of carboxamides in the soybean treatment program helps the producer to manage resistance of the fungus that causes rust to fungicides sold in Brazil. “Carboxamides are a new group and an excellent tool for composing product rotation”, emphasizes Caroline Wesp, PhD in phytopathology and researcher at CCGL Tecnologia.

Manoel Pedrosa, from DuPont, recalls that the application of multisite fungicides is also recommended for the effective control of oilseed diseases. “Multisites play a decisive role in the resistance management strategy. The producer should also not make more than two applications of carboxamide-based fungicides per soybean cycle”, warns the agronomist. Other important recommendations, according to him, are respecting the sanitary void, planting varieties with genetic tolerance and a short cycle and the adoption of good product application technologies.