Alwyn E. Wolfarth will retire as assistant treasurer and director, pension asset management, at Monsanto Co., St. Louis. He will be replaced by Gary Stentz, director, pension asset operations. Mr. Wolfarth, who has been involved with managing Monsantos fund for more than 20 years, said he will continue to work in the investment management industry as a consultant after his retirement. Monsanto manages $1.5 billion in U.S. defined benefit assets, $2.3 billion in U.S. defined contribution assets, and about $700 million in non-U.S. pension assets. Mr. Stentz couldnt be reached for comment.