MANAGEMENT OF EMERGING WEEDS WITHIN WESTERN AUSTRALIAN WHEAT BELT

A recent comprehensive survey on the changes in weed spectrum within the Western Australian (WA) wheat belt shows that some emerging weeds species are becoming more problematic. A study was conducted at two locations within WA over three years to develop management practices for barley grass, brome grass (great brome) and silver grass within the WA wheat belt. In the rotation trial to control barley grass, a lupin-wheat rotation provided more effective suppression of barley grass than a wheat-wheat rotation. The herbicides (simazine, metribuzin, Select®) used in the lupin crop in 2009 provided excellent suppression of barley grass. Consequently, the herbicides used in the wheat crop in 2010 (Sakura 850 WG and Monza®) after the 2009 lupin crop also effectively suppressed barley grass where weed density was effectively reduced in the 2009 lupin crop, leading to yield increases. Sakura 850 WG and Monza® herbicides provided poor control of barley grass where its density was high in 2009, probably due to dry seasonal conditions. In the brome grass (Great brome) control trials, Sakura 850 WG, Boxer Gold® and Triflur Xcel® provided comparable suppression of brome grass plants in a wheat crop in 2009. However, Sakura 850 WG provided the greatest suppression of brome grass seed head production, followed by Boxer Gold® and Triflur Xcel®. Boxer Gold® was more toxic to the wheat crop than Sakura 850 WG or Triflur Xcel® in disc sowing systems when stubble was present in brome grass trials. However, the grain yield of wheat was not affected by early crop damage from herbicides. In silver grass trials, Boxer Gold® suppressed silver grass more effectively than Triflur Xcel® or tank mixes with other herbicides and increased wheat yield by 7 to 17% compared to Triflur Xcel®. Sakura 850 WG was not included in silver grass trials.