Scientists on guard against herbicide resistance

07 October, 2004

Scientists involved in weed studies with the Cotton and Weed Management Co-operative Research Centres have developed a framework to assess the potential for glyphosate resistance in Roundup Ready® cotton farming systems.

__Presenting a paper to the recent Australian Weeds Conference in Wagga, PhD student, Jeff Werth, noted that Roundup Ready cotton was introduced in cotton almost four years ago, and the industry is anxious that its use does not result in resistance or a shift in weed species due to changes in herbicide selection pressures.

To analyse these developments, a research team from the Cotton CRC and the CRC for Australian Weed Management monitored two popular weed species under integrated weed management, with and without Roundup tolerant technology.

A grower survey was also conducted in NSW and Queensland to assess how the introduction of Roundup has impacted on weed species, weed management and herbicide use.

The survey found little change in weed species between fields to this time, but the research team noted that four seasons may be too early to observe weeds species shifts.

The survey did find a marked increase in the use of Roundup, but the total volume of herbicides used in these crops was lower, due to reductions in both pre-emergent and post-emergent herbicides.

The research team’s investigation of the population dynamics of weeds, and the impact of management practices, using barnyard grass and liverseed grass as model weeds, is ongoing.

It comprises an IWM approach with and without Roundup Ready technology, a half-IWM approach with Roundup Ready, and utilising Roundup Ready only.

The team believes these experiments will lead to the development of a model predicting the likely evolution of glyphosate resistance, initially for grass species and later for a range of weed species in cotton systems.

The end result will be to facilitate the development of sustainable weed management practices in Roundup Ready cotton.

The research team comprises Jeff Werth (University of Adelaide and the Cotton and Weed CRCs), Christopher Preston (University of Adelaide and the Weeds CRC), Grant Roberts (Cotton CRC/CSIRO), and Ian Taylor (Cotton CRC/NSW Department of Primary Industries).

Further information: Grant Roberts 02 6799 1500