Rigid ryegrass (Lolium rigidum) abundance in Tunisian Northern cereal fields and its susceptibility to selected inhibitors of acetolactate synthase (ALS) and acetyl coenzyme A carboxylase (ACCase). Khammassi, M., Chaabane, H., Bousselmi, A., Belbahri, N., and Souissi, T. (Tunisia)

Abstract

Rigid ryegrass (Lolium rigidum) is one of the most prevalent grass weed in cereal crops in Tunisia. The study was undertaken to determine its occurrence in the Northern regions of the country and to evaluate its susceptibility to selected commonly used herbicides inhibitors of acetyl Coenzyme A carboxylase (ACCase) and acetolactate synthase (ALS). The frequency of infested surveyed fields by this weed is 32%. Its abundance varied among locations and bioclimatic stages. High weed infestations (> 300 individuals/m²) were located in the Northern regions of Bizerte and Bejà where weather conditions, namely the rainfall, are the most favorable. None of the tested herbicides whether in field trials or in pot experiment gave a satisfactory control of rigid ryegrass. Over 80% of tested ryegrass populations in pots were resistant to clodinafop-propargyl and iodo-mesosulfuron, with high proportions of resistant plants to both tested herbicides, suggesting that rigid ryegrass has evolved resistance to herbicides commonly used to control weeds in wheat fields.

Keywords

• ALS and ACCase inhibitors
• rigid ryegrass
• Tunisia
• wheat