Barnyard grass responses to glyphosate - the importance of morphological traits

The genus 'Echinochloa' includes the species 'E. colona' (L.) Link and 'E. crus-galli' (L.) Beauv. Both are common summer weeds in farming systems of the northern grain region of Australia. Commonly referred to as barnyard grasses, these species are widespread problems within the region. Glyphosate is commonly relied upon for fallow control of these species. However, farmers are achieving variable control of barnyard grass with glyphosate. In addition, management of barnyard grass in Australia has become an important issue due to the development of populations resistant to glyphosate. Barnyard grass populations are variable in morphology and this may be a cause for differences in glyphosate efficacy. Field surveys found that within populations, individual plants had differences in characteristics such as growth form, culm thickness, and the presence/absence of banding on the leaves. Plants were categorised into one of five growth forms: erect, semi-erect, or prostrate and two intermediary forms, semi-erect/erect or semi-erect/prostrate. The aim of this study was to assess the relationship between plant morphology and their response to glyphosate.