Asian soybean rust in Brazil: resistance in the 2025/26 season

Estimates for Mato Grosso show production costs peaking at US$602 per acre in 2022/23. Costs were about US$559 per acre in 2025/26, and profit is projected near US$10 per acre. On those figures, there is very little room to absorb a loss.

Transport adds to the pressure. Estimates put the cost of trucking at US$8.02 per tonne per 100 miles in 2025, up 9%. Every pest and disease loss therefore comes straight out of a narrow margin. Crop protection is a financial question as much as an agronomic one.

Asian soybean rust remains the priority disease. The Anti-Rust Consortium recorded 379 cases in 2025/26, roughly triple the previous season. That is a sharp rise in a single year.

The fungicide picture is harder. Brazilian isolates of the rust fungus have shown multiple resistance to three fungicide groups: DMI, QoI and SDHI. Resistance to more than one group at the same time limits the options available for rotation.

Field results reflect this. Across 21 cooperative trials run by 23 institutions, registered fungicides controlled rust by only 62% to 80%. Regulators also expect proof: Brazilian regulators suspended 63 rust fungicides in 2017. Any rust programme has to show its evidence in the field before it earns a place in the market.

Rust is not the only concern. Stink bug control relies on three chemical groups, which narrows the choices for rotation. Embrapa has documented resistance in the brown stink bug.

Weeds show the same trend. Of 809 sourgrass populations tested, 25.96% were glyphosate-resistant. This is why weed programmes now need more than one mode of action.

The competitive landscape is moving quickly. Public information describes four developments, listed at the end of this section. None of them removes the need for rotation.

Each new molecule adds one more mode of action, and resistance can develop to any of them when it is used alone. IRAC-Brazil promotes a window approach to rotating modes of action in stink bug control.

Sulfoximines (IRAC 4C) are reported to show low cross-resistance with neonicotinoids, which makes them a candidate rotation partner. The practical lesson is to plan across non-overlapping modes of action rather than to rely on any single new molecule.

1. A tetrazolinone QoI fungicide, which its developer describes as effective despite QoI-resistance mutations. It was still in registration in 2025 and was presented as a launch in March 2026, so its status should be confirmed.
2. Isocycloseram (IRAC 30), an insecticide that arrived in 2023.
3. Dimpropyridaz (IRAC 36), registered since December 2024, including for soybean whitefly.
4. A broflanilide caterpillar insecticide, announced and due within two to three years.

White mould needs its own plan. Fluazinam was effective in Embrapa trials, and Trichoderma and Bacillus biological products are used alongside it. For any product, follow the registered label and local extension advice.

Weed programmes layer different tools. They combine PPO and long-chain fatty acid residual herbicides with post-emergence products that have different modes of action. The reasoning is the same as for fungicides and insecticides: no single mode of action should carry the whole programme.

Chemistry is one pillar of crop protection, not the whole plan. The sanitary period, early sowing and resistant cultivars sit beside it. Local extension services set the rules that apply in each region.

Digital tools are designed to strengthen every part of this plan. Weather-driven disease-risk models, drone and satellite scouting, leaf-image diagnosis and resistance dashboards all aim to help growers decide when and where to act. The decision stays with the grower, within the registered label and local extension advice.

Variable-rate application aims to protect margins by matching inputs to the needs of each part of a field. These tools are only as good as the evidence behind them. A disease-risk model, for example, needs local validation before anyone relies on it.

SYGOPLUS is Fertivero's global R&D programme with international laboratories. It is in development. Fertivero's global R&D, which runs from Copenhagen, studied evidence from Brazil's research network, including Embrapa Soja, Fundação MT, Coamo and Desafios Agro. It then built SYGOPLUS as an integrated programme rather than a single product.

For rust, SYGOPLUS is designed to rotate DMI, QoI and SDHI fungicides with multisite partners, as Embrapa recommends, and to be benchmarked against tetrazolinone QoI chemistry. For stink bugs, it is designed to follow the IRAC-Brazil window approach and to evaluate sulfoximines as a rotation partner. The focus is rotation across non-overlapping modes of action, not any single new molecule.

Every candidate goes through laboratory, greenhouse and multi-location field testing. It is then registered with MAPA before sale. Registered before sold. SYGOPLUS aims to help protect yield, delay resistance and lower cost per bag, and we make no performance claim until a named trial supports it. If you work in Brazilian soybean and want to share field evidence or ask a question, write to info@fertivero.com.

1. Conab — 12th crop survey, released on 15 September 2026, Brazil 2025/26 soybean estimate of 180.4 million tonnes
2. Industry estimates — Mato Grosso production costs and projected profit per acre, and trucking cost per tonne per 100 miles in 2025
3. Anti-Rust Consortium — 379 rust cases recorded in 2025/26
4. Cooperative fungicide trials (21 trials, 23 institutions) — rust control by registered fungicides of 62% to 80%
5. Brazilian regulators — suspension of 63 rust fungicides in 2017
6. Embrapa — documented resistance in the brown stink bug, fluazinam results in white mould trials, and the recommendation to pair rotated fungicides with multisite partners
7. Sourgrass resistance data — 25.96% of 809 populations glyphosate-resistant
8. IRAC and IRAC-Brazil — mode-of-action groups 4C, 30 and 36, and the window approach to rotation
9. Embrapa Soja, Fundação MT, Coamo and Desafios Agro — Brazilian research network evidence reviewed by Fertivero R&D
10. MAPA — Brazilian regulator for crop-protection registration