Abstract Expanded polystyrene (EPS) beads have been shown to be an effective tool for controlling immature stages of mosquitoes, as well as preventing oviposition by adults. Polystyrene does not biodegrade quickly, resulting in some concerns about its effect on the environment. A potential solution is the use of biodegradable materials that cover the surface of mosquito breeding sites in the same way as EPS beads. Two candidates are polylactic acid (PLA) beads and corn starch shreds. Larval mortality and adult emergence of Culex quinquefasciatus Say (Diptera: Culicidae) were monitored in bowls with each of four treatments: EPS beads, PLA beads, corn starch shreds and a control. The PLA beads were as effective as EPS beads at preventing mosquito emergence, whereas the shredded corn starch treatment resulted in significantly higher rates of emergence to the control. Similarly, EPS and PLA beads resulted in 100% mortality after 10 days, while there was low mortality of larvae in the corn starch (9%) and control treatments (20%). PLA beads provided similar levels of mortality and reduction in adult emergence as EPS beads. However, the production requirements of PLA beads may limit its use in field conditions.