Working for DuPont in the 1950s, Arden Aanestad was at the forefront of a chemical revolution on U.S. farms.

A trained bug expert with a knack for business, he made an early fortune by manufacturing poisons that killed insects and weeds. But in retirement he built a three-decade legacy of volunteerism to protect birds, trees, prairie grasses and wildlife.

"There was a complete paradox there,'' said his son, Chris Aanestad of Hopkins. "Once he was done with the business, he went full on into nature.''

Aanestad, who died Aug. 27, was 86 and fighting cancer.

Aanestad co-founded Castle Chemical Co. in 1960, then retired at age 55 and devoted the rest of his life to environmental causes. He was a birder, a forester and a park naturalist for 30 years at Bloomington's Richardson Nature Center. Even his home in Edina was a sanctuary of ponds, bluebird houses, a bog, butterfly garden and feeders.

"It's a crazy yard,'' said Chris, one of four children raised by Arden and his wife, Phyllis.

In the late 1970s, Aanestad's expertise in pesticides earned him a trip to the Soviet Union on a goodwill tour organized by former U.S. Agriculture Secretary Bob Bergland.

Jennifer Aanestad, a career naturalist herself, said her father always defended his work as necessary to feed the world. But she thinks he was motivated in retirement partly by a realization that farm chemicals were "part of the destruction of some animals.''

The pesticide DDT, banned in 1972 as a threat to bald eagles and other raptors, was one of the poisons he dealt with. Son Jonathan Aanestad of Wayzata said his father was an early doubter about DDT.

Birds topped the list of Arden Aanestad's wide range of interests, his children said. Once an avid hunter of ruffed grouse and ducks, he traded a gun for a camera in middle age, and ultimately won a number of photography awards.

"It was always about the science, but he loved the beauty of it all, too,'' Jennifer said.

Aanestad grew up in north-central North Dakota and learned to hunt with his grandfather, Helge Aanestad, a fire-and-brimstone Lutheran minister. Jennifer said her father asked to be buried at the foot of his grandfather's grave at Roselawn Cemetery in Roseville -- a tribute to the elder's influence.

Aanestad was a lifetime member of the National Rifle Association, a past chapter president of the Izaak Walton League and a past leader of the Ruffed Grouse Society.

On 200 family-owned acres near Emily, Minn., Aanestad worked with a local forester to plant and harvest trees to benefit wildlife. Started in the 1970s, it was one of the first private sustainable forest plans of its kind, his children said. In 2009 he was named Outstanding Tree Farmer by the Minnesota State Tree Farm Committee.

Aanestad was also a master bird bander who contributed 25 years of research data to the Migratory Avian Production Survey and to Project Feeder Watch for Cornell University.

"Educating people about the natural world was his passion,'' said Jane Votca, interpretive naturalist at Richardson Nature Center.

Votca said she got hooked on watching birds after Aanestad caught a tiny warbler and held it up to her ear. "I heard the heart beat and it was one of my most memorable experiences,'' she said.

He was preceded in death by his wife, Phyllis Adele Aanestad, and is survived by his children, Leslie Thoreson, Jonathan Aanestad, Jennifer Aanestad and Chris Aanestad; 10 grandchildren; a brother, Robert, a sister, Corrine; and numerous nieces and nephews. He is also survived by his companion Marge Thomas.

Funeral services will be at 10:30 a.m. Friday at Washburn-McReavy Funeral Chapel, 5000 W. 50th St., Edina, with visitation one hour prior to the service.