Barley grass control with herbicides in subterranean clover pasture. 1. Effect on pasture in the year of spraying

Abstract

Barley grass (Hordeum spp.) in a subterranean clover pasture was controlled with herbicides in the time between the 2-3 leaf stage and flowering. The effects on subsequent pasture production and composition were measured and the interaction between grazing and herbicides was also assessed. Early removal of barley grass reduced dry matter production in winter by an average of 41%. It also allowed an incursion of Indian hedge mustard (Sisymbrium orientale L.). which was suppressed by grazing but comprised an average of 23% ground cover in ungrazed pasture. Loss of total pasture production decreased as the date of herbicide application was delayed from June to September. Broadleaf species compensated for the early removal of barley grass, so that total dry matter production in spring in herbicide-treated areas was higher than in the unsprayed pasture. Fluazifop-p at 32, 53, and 106 g a.i/ha gave, respectively, 94, 91, and 94% reduction in barley grass seedhead density when applied at the 2-3 leaf stage, and 64, 88, and 98% reduction when applied at mid jointing. Application of this herbicide at 53 or 106 g a.i/ha for barley grass control can be delayed until late winter, thereby maintaining winter feed production but avoiding declining palatability and awned barley grass seeds.

The Impact of Herbicide Application and Defoliation on Barley Grass (Hordeum murinum subsp. glaucum) Management in Mixed Pasture Legumes

“…Herbicide efficacy was negatively impacted by seasonal conditions (i.e., drought or frequent rain) and timing of application (i.e., late application to larger plants) resulted in poor control. A single application of propaquizafop timed optimally at early tillering (Zadok's growth stage 21) [36] was most successful in reducing barley grass survival and fecundity during 2016 and 2017, similar to the findings of others regarding ACCase-inhibiting herbicides used against barley grass in mixed pastures [48,49].…”

“…Despite high propaquizafop efficacy in 2016, a small number of barley grass plants survived in 2017 when low rainfall and temperatures likely facilitated rapid maturation of barley grass and reduced propaquizafop activity due to limited translocation, an effect commonly observed in plants treated with ACCase inhibitors during cold and dry conditions [50][51][52][53][54][55][56]. Low subsequent barley grass seedling emergence counts the following year may have also reflected the limited seedbank from barley grass survivors as opposed to low seed viability per se [48,49]. The subsequent invasion of Vulpia spp.…”