Black soybean weevil advances in central Argentina

The black soybean weevil (Rhyssomatus subtilis) has advanced into central Argentina in recent harvests. For two decades, it remained concentrated in northwestern Argentina. Now, records from the National Institute of Agricultural Technology (INTA) and the National Service of Agrifood Health and Quality of Argentina (Senasa) indicate its presence in soybean-growing areas of Córdoba and Santa Fe. Experts link the expansion to the movement of machinery and vehicles between productive regions.

The presence of the insect was first recorded in Argentina during the 2005/2006 growing season in Santiago del Estero. Afterwards, its spread was slow in northwestern Argentina (NOA), with records in Tucumán, Catamarca, and Salta. Between 2022 and 2025, it expanded to new productive areas in northeastern Santiago del Estero. In January 2026, the pest appeared in the southeastern part of the province. In Chaco, the record occurred in the Almirante Brown department.

High alert

The biggest alert came at the end of the 2024/2025 harvest, with detection in north-central Córdoba. In the 2025/2026 harvest, INTA technicians confirmed its presence in the departments of Río Primero, Santa María, and Río Segundo. There was also confirmation in Ceres, in the province of Santa Fe.

According to María Guillermina Socías, from INTA Salta, the geographical shift does not follow a natural pattern of dispersal. The technical hypothesis points to an association with the movement of machinery and vehicles.

The insect has an annual life cycle and accompanies soybeans throughout the crop's development. Adults attack new shoots and can reduce plant growth. The larvae cause the main damage, as they feed on the grains inside the pods. The perforations also facilitate the entry of water and pathogens.

Management requires prevention. Experts recommend crop rotation with grasses and other non-host species. This practice should encompass affected areas and neighboring crops. They also recommend thorough cleaning of machinery and vehicles before moving between production zones. Monitoring should begin early, with inspection of pods, punctures, perforations, larvae, and grain damage.