Methods of reducing ripgut brome seed production and carcass damage

Abstract

Ripgut brome (Bromus diandrus) is an annual grass weed prevalent in dry, hill and high country regions throughout the South Island. Its large seeds contaminate wool and carcasses. Two studies were undertaken in 2006/2007 to test strategies to control and mitigate its impacts. The first study (South Canterbury) tested different rates and timing of application of herbicides on ripgut brome. Glyphosate applied in spring as a spray-topping application (112 g a.i./ha) showed potential as a control strategy, reducing ripgut brome seed production and seedling densities without large increases in bare ground caused by the other broad spectrum and grass selective herbicides. Herbicides had no effect on the cover of perennial grasses, dicots or forbs. In the second study (Marlborough and Central Otago), shearing lambs at weaning reduced the number of carcasses that were detained due to seed contamination (0.33 and 0.41 respectively, proportion of shorn and unshorn carcasses detained) but did not reduce the number of seeds contaminating each carcass. Shearing at weaning, combined with herbicide application targeted at ripgut brome dominant areas may be useful strategies to help reduce seed contamination.