Methods of reducing ripgut brome seed production and carcass damage

摘要

Ripgut brome (Bromus diandrus) is an annual grass weedprevalent in dry, hill and high country regions throughoutthe South Island. Its large seeds contaminate wool andcarcasses. Two studies were undertaken in 2006/2007 totest strategies to control and mitigate its impacts. Thefirst study (South Canterbury) tested different rates andtiming of application of herbicides on ripgut brome.Glyphosate applied in spring as a spray-toppingapplication (112 g a.i./ha) showed potential as a controlstrategy, reducing ripgut brome seed production andseedling densities without large increases in bare groundcaused by the other broad spectrum and grass selectiveherbicides. Herbicides had no effect on the cover ofperennial grasses, dicots or forbs. In the second study(Marlborough and Central Otago), shearing lambs atweaning reduced the number of carcasses that weredetained due to seed contamination (0.33 and 0.41respectively, proportion of shorn and unshorn carcassesdetained) but did not reduce the number of seedscontaminating each carcass. Shearing at weaning,combined with herbicide application targeted at ripgutbrome dominant areas may be useful strategies to helpreduce seed contamination.