Arkansas will temporarily ban the use and sale of the weed killer dicamba after a rise in complaints that the agricultural chemical is drifting into neighboring fields and damaging crops, the state's agriculture department said on Friday. The emergency 120-day ban of dicamba, produced by Monsanto Co, Germany's BASF and others, will go into effect as soon as paperwork is filed with the Arkansas Secretary of State, said agriculture department spokeswoman Adriane Barnes.