Sustainable weed management in cotton farming systems is critical to the long-term production of profitable, high yielding cotton crops. The introduction of Roundup® Ready cotton in 2000 has seen a major shift in weed management in cotton, with greatly increased reliance on glyphosate for weed control, frequently at the expense of diversity in the cotton weed management program.

Roundup Ready cotton provides growers with a number of advantages, including:

– Earlier planting opportunity, with less time dedicated to weed management between spring weed emergence and planting

– Control of weeds which were previously more ‘difficult’ to control e.g. nutgrass

– Less crop yield impact from residual herbicides

– Reduction in the use of chipping and interrow cultivation

– More simple and ‘easy’ weed management program.

In parallel with and prior to the adoption of Roundup Ready crops, many cotton and adjoining paddocks and farms were also increasing their reliance on glyphosate with the conversion to zero till management in the non-cotton phase and/or prior to establishing cotton.

The high reliance of glyphosate has seen three major trends:

– Species shift towards surface germinating weeds in no-till farming

– Species shift towards weeds with higher levels of tolerance to glyphosate

– Selection of weeds resistant to glyphosate.

An increasing number of cotton growers are experiencing glyphosate control ‘failures’ on certain weeds on parts of their farms. Through travel, some growers have also been exposed to the glyphosate resistance issues (Palmer Amaranth in particular) currently being experienced in North American cotton systems.

This has increased the level of urgency to address the lack of diversity in weed management. As a reflection of this demand, ICAN has recently been approached by a number of cotton advisers to assist them in facilitating discussions on increasing diversity in weed management processes with their cotton grower clients.