To evaluate residual control of button grass in fallow

This trial was conducted to evaluate the residual control of button grass in fallow. An establishment of button grass was already present at the site with the majority of weeds ~15-25cm in diameter. These weeds were controlled with Roundup 450 @4L/ ha + Liase @1%. Residual treatments were applied on the 19/11/18, 5 days after the Roundup application.
Significant rain events occurred 3 days after residual application (52mm) and 29 days after application (30mm). There was no new emergence of button grass even in the untreated areas. A second maintenance spray of Roundup was applied to control any surviving mature button grass plants ~30 days after the residual herbicide application. Assessment on the 5/2/19 (77 days after application) still showed no new button grass emergence.
Additional rain events occurred in March 2019 (85mm on 16/3/19 and 35mm on 30/3/19) with an assessment of control conducted on the 1/5/19 (163 days after application). The majority of button grass at this assessment were flowered, up to ~30cm in diameter and expected to have emerged following the March rainfall. Dual Gold 2L provided ~99% control of the emergence flush with Flame at 150-200 mL/ha in excess of 90% control. Stomp Xtra and Valor provided useful levels of suppression and controlled ~70-80% of the emergence. Neither Balance 100 g/ha nor Terbyne Xtreme 1.2 kg/ha provided any button grass control and there was no obvious indication of biomass suppression.