On Sunday night, airplanes dropped the pheromone solution over areas of Marina and Seaside.
The spray does not kill the pest but confuses male light brown apple moths, keeping them from mating and reproducing.
State officials say the eradication project is necessary to protect hundreds of plants and crops the moths feed upon.
The potential cost of damages if the moth is not controlled could surge into the millions of dollars, according to state officials.
Residents in the area have expressed concern over potential ill effects the spray could have and people, animals and the environment.