Control of the recentlyintroduced weed butterprint (Abutilon theophrasti) in maize

Butterprint (velvetleaf in many countries) is one of the worst broadleaf weeds in maize (Zea mays) and soya bean (Glycine max) crops in USA It has been accidently introduced into New Zealand on several occasions Recently it has been found in three maize fields in Waikato and has become well established at one 20 ha site Twelve different postemergence herbicides were evaluated for control of butterprint in glasshouse pot trials and in a field trial In the glasshouse bromoxynil dicamba mesotrione aminopyralid and topramezone all gave 100 control In the field trial dicamba showed the most activity but overall efficacy was less than in the glasshouse Dicamba controlled most of the plants that were present at spraying but germination over the next month resulted in a final population of 88 of the original This population of butterprint also shows a very high tolerance to atrazine when treated postemergence