Andrew Paul Gutierrez, an entomologist and ecologist whose farm modeling changed the way scientists and agricultural producers control pest outbreaks without using pesticides, died on June 7, 2026. He was 86.
Gutierrez was born on January 25, 1940, in Arizona. A graduate of Winslow High School, Gutierrez earned a BS in Zoology from Arizona State College (now Northern Arizona University) in 1962, and later attended UC Berkeley for graduate school, earning his PhD in entomology in 1968. Before joining Berkeley’s Division of Biological Control as a professor of entomology in 1976, Gutierrez worked at Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO), Purdue University, the Institute of Animal Resource Ecology at the University of British Columbia, and UC Davis.
Gutierrez’s research contributions span decades and focus on systems ecology, population dynamics, and designing sustainable pest management strategies that integrate biological, environmental, and economic factors. A central element of his approach was studying a farm as a single system rather than a collection of separate problems. Specifically, his mathematical models combined how plants, insects, predators, and parasites respond to changing conditions across the growing season. This approach initially helped researchers understand the spread of aphid-borne plant viruses in southeastern Australia, and was further refined to account for how plants allocate nutrients and water availability.
A leading figure in integrated pest management (IPM), Gutierrez was the founding chair of the statewide committee that created the University of California's Integrated Pest Management Program (and later served as its associate director). While much of his work initially focused on reducing reliance on synthetic pesticides in California agriculture, he also developed models to cover staple and commercial crops grown worldwide. For most of the 1980s, Gutierrez was involved in an international effort to control the cassava mealybug throughout a broad area of Africa known as the Cassava Belt, led by the Centro Internacional de Agricultura Tropical (CIAT) and the International Institute for Tropical Agriculture (IITA). His contributions helped protect a staple crop for hundreds of millions of people in sub-Saharan Africa. The Belgian government recognized these efforts in 1990 with its King Baudouin Award for International Agricultural Research.
An accomplished field ecologist, Gutierrez and his collaborators gathered exhaustive data for crop systems including alfalfa, cotton, and beans. He trained 23 PhD students and 24 postdoctoral fellows, many of whom became leading scholars and researchers. He was recognized in 1988 with the Parasitis Award; with UC Berkeley’s Robert van den Bosch Medal in 2011; and elected a Fellow of the Royal Entomological Society of London in 2017.
After retiring from UC Berkeley in 2008, Gutierrez founded the Center for the Analysis of Sustainable Agricultural Systems (CASAS), which turned the demographic models he developed for crop systems into tools to predict how global climate warming alters ecosystems. A major goal of these efforts was to show how shifting weather patterns change the geographic ranges of agricultural pests and undercut the natural enemies that hold them in check.
Gutierrez is survived by his wife, entomologist Marina A. Pizzamiglio-Gutierrez, sons Paul and Barry, daughter Lorrie (Steve Williams), grandchildren Nicholas and Riley (Alyssa), two sisters, and a brother.