Advances in biotechnology in cotton cultivation and safety in the management of ratoon crops

Brazilian cotton farming has stood out on the global stage, driven by high productivity and the adoption of innovative technologies that promote sustainability and efficiency in the sector. In the 2023/2024 harvest, Brazil took the lead as the world's largest cotton exporter, an unprecedented feat that consolidates the country as an important player in the global market.

Biotechnologies such as Bollgard, the first version of which was launched in Brazil almost 20 years ago, have represented a significant advance in pest protection and driven the growth of the sector. At the 14th Brazilian Cotton Congress, Bayer presented the Bollgard 3 XtendFlex (B3XF) platform, maintaining protection against the main caterpillars targeted by cotton crops and increasing tolerance to herbicides - being the first cotton biotechnology tolerant to glyphosate, glufosinate ammonium and dicamba.

This tolerance to herbicides offers greater flexibility in management, reduces weed competition and ensures greater assertiveness in weed control. Tests carried out indicated that cotton growers who adopted this biotechnology obtained an increase in productivity of approximately 11 arrobas of lint per hectare. This is the result of the combination of integrated management with dicamba in desiccation, glufosinate ammonium and glyphosate in post-emergence to genetics with high productive potential.

The biotechnology was developed to support cotton farmers in the challenges of tropical agriculture, from pre-planting to post-harvest, including crop protection and seed protection. B3XF was made available in the 2024/2025 harvest with varieties adapted to the main cotton-producing regions in Brazil.

Quality standard in ratoon management

In cotton farming, the safety of cotton stubble management is a concern for cotton growers. The destruction of cotton crop residues after harvest is a recommended practice as a measure to reduce pest and disease populations during the off-season. Stubble destruction occurs through cultural, mechanical, chemical methods and through the integration of methods, with chemical destruction being the most widely used due to operational yield and control benefits.

This process is divided into three stages: at the stump, the plants are cut 20 to 30 centimeters from the ground and sprayed immediately, which requires constant monitoring for possible reapplications; at regrowth, where spraying is carried out when the regrowth reaches between 5 and 8 centimeters in height, paying attention to the stage of phytosanitary risk; and standing plants, without prior mowing, with herbicide application when the regrowth is uniform, considering the same size and monitoring criteria as for regrowth.

Regardless of the chemical destruction method, one of the most commonly used active ingredients to eliminate cotton ratoon weeds is 2,4-D, applied alone or in combination, sequentially. Other herbicides are usually added in the second application to enhance the effectiveness of ratoon weed control.

Regarding the adoption of Bollgard 3 XtendFlex technology coupled with the use of 2,4-D, there are no changes in the chemical destruction practices of ratoon crops. This is confirmed by Technical Circular No. 62, recently published by the Mato Grosso Cotton Institute (IMAmt). In other words, producers who use B3XF can follow the same application protocols as 2,4-D, without the need for adjustments to their operations.

In 2020, IMAmt conducted three experiments to evaluate ratoon control with a Bollgard 3 XtendFlex line compared to a commercial variety without dicamba tolerance. The studies were conducted at IMAmt's experimental stations in Primavera do Leste, Sorriso, and Rondonópolis, in Mato Grosso. Treatments included standard ratoon destruction management, with the first application made to the stump - immediately after mowing the plants - and standard ratoon destruction management with the first application on the regrowth, without application immediately after mowing.

The experiment did not identify significant differences in the evaluation of regrowth in the treatments applied to the B3XF line and the commercial variety without dicamba tolerance. The results demonstrated that the standard management of ratoon destruction, based on the use of the herbicide 2,4-D, was efficient in plants with the B3XF technology.

In 2023, new trials were conducted at the IMAmt experimental stations in Primavera do Leste, Sorriso and Sapezal. The experiment compared a Bollgard 3 XtendFlex line with another commercial variety without dicamba tolerance. The standard destruction management, with the first application on the stump after mowing, proved to be efficient, resulting in low percentages of regrowth in the final evaluation in both technologies. The results confirmed that the chemical destruction management based on 2,4-D is effective in eliminating cotton ratoon plants with the B3XF technology.

The IMAmt Technical Circular serves as a safe guide for cotton growers, and ensures that ratoon destruction operations are carried out efficiently and in compliance with the legal parameters established by the cotton crop health gap. Bollgard 3 XtendFlex is a biotechnology that helps producers face the challenges of tropical cotton farming to improve productivity and sustainability in the field.

* By Fernando Prudente, executive director of cotton for Bayer's agricultural division