MDA entomologist urges source reduction as best defense against Asian tiger mosquitoes in College Park

Gene Zastrow, an entomologist with the Maryland Department of Agriculture’s mosquito control program, told College Park residents on July 9 that the state’s approach emphasizes integrated pest management and community source reduction as the most effective way to limit nuisance and disease-carrying mosquitoes.

“Only female mosquitoes bite because they need the blood for eggs,” Zastrow said, explaining basic mosquito biology and why reducing breeding sites matters. He described roughly 60 species in Maryland across about 10 genera and said only about 10 species are of concern for vectoring disease.

Zastrow said two established mosquito-borne threats in Maryland are West Nile virus and eastern equine encephalitis (EEE). “About 20 percent of the people infected develop symptoms,” he said of West Nile; he also noted EEE’s high impact on horses and severity in human cases. Zastrow added that malaria and viruses such as Zika and dengue are typically travel-related when they appear in the state.

On control tactics, Zastrow said the MDA program prioritizes methods with lower environmental impact: biological controls, biorational larvicides such as BTI and insect growth regulators, and targeted use of conventional pesticides when necessary. Larviciding is typically reactive—MDA treats sites where crews find active breeding—but some persistent sites are treated preemptively.

Regarding truck-based adult spraying, Zastrow described criteria that must be met before the state conducts an application: either mosquito populations exceed defined thresholds or there is a known disease threat. He said state truck fogging is timed for evening or night to reduce risks to pollinators and that the fog’s knockdown effect lasts “about 30 to 40 minutes,” after which the material disperses.

Zastrow also explained the state’s opt-out policy for standard nuisance applications: residents may request not to be sprayed and MDA will record addresses and establish a 300-foot buffer zone around opt-out properties. He emphasized that any exemptions are suspended during a disease-response application.

The entomologist singled out the Asian tiger mosquito (Aedes albopictus), introduced to Maryland in 1987, as a common cause of daytime biting and neighborhood nuisance. “They will breed in as little as a teaspoon of water,” Zastrow said, pointing to common containers—recycling bins, clogged gutters, plant saucers, corrugated drain pipe and tires—as frequent local breeding sites. He said Asian tiger mosquitoes generally fly about 200 meters from where they hatch, so neighborhood-level cleanups can substantially reduce local populations.

Zastrow recommended household steps—weekly yard checks, tipping or removing water-holding containers, screens on doors and windows, stocking ornamental ponds with fish such as fathead minnows (with a free permit available via the Department of Natural Resources), and the use of proven repellents such as picaridin or oil of lemon eucalyptus. He discouraged reliance on broad-spectrum, long-residual pesticides used by some private companies unless applicators hold mosquito-specific certification.

Residents raised concerns about fairness and health trade-offs when neighbors opt out of spraying. One attendee said, “I’m 70 years old with major health problems, and I have a neighbor within 300 feet of my house that does not like to be sprayed … Which puts me in more jeopardy.” Zastrow advised first trying to negotiate with neighbors about reducing individual buffer zones and, failing that, organizing community petitions that can be reviewed by the Secretary of Agriculture; he also suggested contacting local municipal or county officials if breeding is tied to public stormwater infrastructure.

On notifications, Zastrow said cities typically publish zone maps and announce scheduled treatment nights on social media or city communication channels and that residents can contact their local mosquito control office to confirm schedules and participation.

The session closed with Zastrow directing attendees to MDA and University of Maryland Extension resources and offering to check with his public information officer about sharing the recorded talk. The city moderator said the meeting recording would be posted on the city website under committee materials.

The MDA contact number Zastrow referenced covers Prince George’s County and central/western Maryland; residents seeking inspections or information were told to call that office or the College Park mosquito-control office to confirm participation and notification procedures.