Responses of Lolium spp. to glufosinate ammonium application at different temperatures

An experiment to investigate why glufosinate ammonium control of Lolium spp. is more effective at cooler temperatures than warmer temperatures was conducted at Welgevallen Experimental Farm, Stellenbosch University. Wild Lolium spp. was grown at 10/15, 15/20, 20/25 and 25/30°C (night and day) temperature regimes and treated with glufosinate ammonium at 0, 300, 600, 900 and 1,200 g a.i./ha, 6 weeks after planting. Control of Lolium spp. decreased with increasing temperature. Results from elemental analysis, scanning electron microscopy (SEM), fluorescence imaging and gas chromatography–mass spectrometry (GCMS) investigations allude to calcium accumulation, cuticle thickness and plant phenolic compounds playing roles in the response of Lolium spp. to this herbicide. Increased cuticle thickness and calcium accumulation as temperatures increase indicate promotion of plant defence mechanisms through increased phenolic compound production, which is induced by herbicide stress, hence resulting in poor control of Lolium spp. under warmer temperatures.