Ciba-Geigy, a predecessor of Syngenta, had a confidentiality agreement with Agroscope, and insisted that she keep the research secret, she said. Confidentiality agreements are not unusual for Agroscope. In one such agreement obtained by The Times, the agency agreed to return or destroy corporate documents it received as part of a research project.

Dr. Hilbeck said she refused to back down and eventually published her work. Her contract at Agroscope was not renewed. An Agroscope spokeswoman said the episode took place too long ago to comment on.

Dr. Hilbeck continued as a university researcher and was succeeded at Agroscope by Jörg Romeis, a scientist who had worked at Bayer and has since co-authored research with employees from Syngenta, DuPont and other companies. He has spent much of his career trying to debunk Dr. Hilbeck’s work. He followed her lacewing studies by co-authoring his own, finding that genetically modified crops were not harmful to the lacewing.

Next, after Dr. Hilbeck co-wrote a paper outlining a model for assessing the unintended risks of such crops, Dr. Romeis was lead author of an alternative approach with a Syngenta scientist among his co-authors.

Then, in 2009, Dr. Hilbeck was an author of a paper looking at risks to ladybug larvae from modified crops. Dr. Romeis followed by co-authoring a study that found “no adverse effects” to ladybug larvae. In subsequent publications, he referred to work by Dr. Hilbeck and others as “bad science” and a “myth.”

“They were my little stalkers,” Dr. Hilbeck said. “Whatever I did, they did.”

In an interview, Dr. Romeis, who now leads Agroscope’s biosafety research group, said, “Her work does not affect our mission in any way,” adding that the idea of researching the effects of genetically modified crops was “not patented by her.”

Refereeing a scientific dispute is difficult. But Dr. Romeis and his collaborators do seem preoccupied with Dr. Hilbeck’s work, judging from a review of email traffic between Agroscope and the U.S.D.A. obtained by The Times after a Freedom of Information Act request.