Safe recropping after Lontrel in winter crop systems in southern Australia

摘要

Lontrel Herbicide (300 g a.e. L~(-1) clopyralid) has been widely used in southern Australia for control of weeds of the Asteraceae and Fabaceae families, in winter crops such as cereals and canola. It is commonly used at 75-150 mL ha~(-1) as a tankmixpartner with other broadleaf herbicides in winter cereals, or at up to 300 mL ha~(-1) in canola. It has moderate persistence in the soil and is broken down by microbial activity. Breakdown is fastest under warm, moist soil conditions. Concerns had beenexpressed about the potential of Lontrel to carryover to subsequent susceptible crops and cause injury. Dow AgroSciences conducted six trials to determine whether label recommendations for safe plantback periods for sensitive crops were valid. Results showed that currently labelled plantback periods were safe for susceptible crops. Nine months was required for safe planting of sensitive crops after 300 mL ha~(-1) Lontrel was applied. This paper summarises those trials and shows new recommendations for the registered product label.