Integrated strategies, such as controlling seed sets, may reduce the frequency of glyphosate resistance in ryegrass, according to a new report in the most recent issue of Weed Science.

Glyphosate is the most widely used herbicide in the world and is often applied to plants that readily develop resistance to other treatments. However, certain ryegrass species, once effectively controlled by glyphosate, have evolved to resist even its application. This report focuses on a review of the evolution of glyphosate resistance in ryegrass, the mechanisms of this resistance, and suggestions for the management of ryegrass.

The over-reliance on glyphosate to control certain ryegrass species, even to the exclusion of other practices, has enabled the plant to develop a resistance to the herbicide. Two resistance mechanisms have been determined: reduction of the translocation of glyphosate to the shoot meristem and roots, and modifications in the target site on the EPSPS gene. It also appears as though a cross between individuals carrying each of these mechanisms results in a multiple resistance to glyphosate.

Research into management of ryegrass has shown that glyphosate-resistant plants do suffer a fitness cost, however, which can be exploited by using integrated strategies such as herbicide rotation and crop competition to control the plant.

To read the entire article, “A Decade of Glyphosate-Resistant Lolium around the World: Mechanisms, Genes, Fitness, and Agronomic Management” (Vol. 57(4):435-441, 2009), visit http://www.allenpress.com/pdf/wees/WEES_57.4_435_441.pdf.