Dennis R. Hamel, 46, an entomologist and pesticides specialist who had worked for the Agriculture Department's Forest Service since 1974, died Jan. 10 at Arlington Hospital. He had AIDS.

He was an authority on the use of pesticides in forestry and had lectured internationally on the topic. He received a 1986 Presidential Award for Volunteerism and a 1982 Agriculture Department Superior Service Award.

He was a member of the Entomological Society of America and the American Forestry Association.

He wrote several books for the Forest Service and had contributed articles to such journals as the American Entomologist.

He also was the author of the Gypsy Moth Workbook, a publication for children.

At the time of his death, he was working on an almanac of the world's insects.

Mr. Hamel, a Falls Church resident, was a native of St. Ignatius, Mont., and an Army veteran. He was a graduate of Montana State University and received a master's degree in entomology from Texas A&M University.

He worked for the Forest Service in Montana before coming here in 1978.

His hobbies included stamp collecting and gardening. He had written magazine articles on those topics and belonged to several organizations devoted to those endeavors, including the Potomac Bonsai Association.

His marriage to Molly Hamel ended in divorce.

Survivors include his companion of 11 years, David Alligood of Falls Church; a son, Anthony, of Clarkston, Wash.; his parents, Robert and Esther Hamel of St. Ignatius; and a sister, Kay Kelley of Billings, Mont.