In the 1970s, she attended University of California, Davis for two years then relocated to the UC Berkeley where she studied and worked as a practicing entomologist and science writer prior to obtaining her Ph.D. in entomology in 1974.
During her academic career at Cornell, Hajek ran an active research program in both laboratory and field studies and led as many as 200 people.
[2] In 1999, Ann E. Hajek published her study on Entomophaga maimaiga and how it can be used to control the spread of the spongy moth (Lymantria dispar).
[3] In 2019, Prof. Hajek along with fellow scientists from Ohio State University studied spotted lanternfly which is an abundant pest known to damage grape and apple crops in China, Taiwan, and Vietnam and had invaded South Korea and Japan.
While studying how the insect feeds on the tree of heaven, Hajek and her team discovered an outbreak of Beauveria bassiana and Batkoa major, two species of native fungal pathogens, which appear to have potential to control the growing populations of lanternflies; Batkoa major killed lanternflies on trees while Beauveria bassiana killed those on the ground, with only a few viable egg masses produced in the fungal outbreak area.