To evaluate residual control of tall fleabane in fallow

Only Valor 280 g/ha provided a significant reduction in common sowthistle counts compared to the untreated. Neither Dual Gold alone or the experimental Group 27 herbicide showed any suppression of common sowthistle numbers, at either assessment.
Low fleabane numbers were present at 80 DAA with untreated populations of tall fleabane at 0.2/m2 and flaxleaf fleabane at 1.7/m2. There were no significant differences for either species.
A new cohort of tall fleabane was present 3 months later when a final count of weeds was made at 172 DAA. An additional 254 mm of rain had been recorded between assessments 2 and 3. Although tall fleabane counts were still low, there was no apparent effect from any herbicide.
At this site, with very high levels of groundcover from the 2021 wheat harvest and ~170 mm of rainfall in the first month after application, no herbicide showed useful residual activity against either tall or flaxleaf fleabane. 

Valor 280 g/ha was the only treatment to provide significant control of a trace population of common sowthistle at 80 DAA.