New York City Department of Health

Q: What are larvicides?
A: Larvicides are chemicals or natural bacteria that can be applied to kill mosquito larvae.

Q: What are larvae?
A: Larvae are one of the four forms in a mosquito's development. Adult mosquitoes lay eggs, which hatch into larvae; larvae then become pupae, from which the adult mosquitoes emerge. Adult mosquitoes lay their eggs on surfaces of standing water and the larvae live and develop into pupae in the water.

Q: In what form are larvicides used?
A: Larvicides can be applied to standing water as liquid, a spray, granules or briquettes. A briquet is a block that is placed in the water where mosquitoes breed. The briquette releases concentrated larvicide slowly over weeks to months.

Q: Where are larvicides used to kill mosquitoes?
A: The New York City Department of Health will apply larvicides to water in which mosquitoes can breed. It will primarily use the briquette and granule forms of larvicides in catch basins (storm drains) in which standing water has developed. The products will be place into the storm drains by hand. For other types of standing water, granules or liquid products may be applied either by hand, or sprayed from backpacks or trucks. For borders of stagnant water in wetlands, swamps and marshes, where access may be difficult, larvicide may be sprayed from a helicopter.

Q: Are larvicides any better at killing mosquitoes than pesticides that attack adult mosquitoes (adulticides)?
A: Larvicides are more effective at controlling mosquitoes because they kill mosquitoes before they become adults and disperse.

Q: What types of larvicides will the New York City Department of Health be using to combat the spread of mosquitoes with the West Nile Virus?
A: The three larvicides to be used this spring are Altosid (Methoprene), Vectolex (Bacillus sphaericus), and Vectobac (Bacillus thuringiensis israelensis). These products have been approved for mosquito control by the US Environmental Protection Agency and NYS Department of Environmental Conservation. Altosid mimics an insect growth hormone and prevents the development of adult mosquitoes from pupae. Vectolex and Vectobac contain a bacteria that can damage the gut of the mosquito larvae that feed on them, causing the larvae to starve to death. All three have been found to be highly effective in mosquito control. The New York City Department of Health has created fact sheets with information on each of these larvicides.

Q: When will these larvicides be used for mosquito control?
A: Initial application of the larvicides will take place during the last two weeks of April 2000 and through mid-May 2000. Follow-up applications will take place periodically afterwards, and after heavy rains. Some areas will not receive persistent larvicide applications to protect sensitive aquatic and wildlife.

Q: If we use larvicides for mosquito control now, does that mean the use of pesticides for adult mosquitoes won't be needed later on?
A: The use of larvicides is part of our first line of defense against mosquitoes carrying the West Nile virus. A preventive approach also includes encouraging residents to eliminate standing water areas around residences where mosquitoes breed and placing mosquito larvae eating fish in some areas. In the event of a public health threat, reducing the adult population of mosquitoes with EPA approved pesticides will be done when necessary to prevent or address the potential for illness in humans.

Q: Are these larvicides available to the public for home use?
A: Some local hardware stores may carry a product called Mosquito Dunk that contains a larvicide - Bacillus thuringiensis israelensis (BTI) - for use in areas of standing water around the home. The City Department of Health recommends eliminating standing water around the home to reduce breeding sites for mosquitoes and warns that direct handling of larvicides may cause skin and eye irritation. If these products are purchased for home use, we recommend careful reading of the hazards label, directions, and details regarding storage and handling.

Q: Am I likely to be exposed to these larvicides?
A: No. The larvicides are being applied in storm drains, catch basins and other areas to which the general public does not have access. Larvicides will not be applied in areas that drain into waters consumed by humans.

Q: What problems could I have if I am exposed to these larvicides?
A: Altosid, as well as Vectolex and Vectobac, can cause mild eye and skin irritation, but mostly through direct contact with highly concentrated forms of these agents. The City will apply these larvicides to areas inaccessible to the public and at low concentrations.

Q: What should I do if I am exposed to these larvicides?
A: If you experience eye or skin irritation as a result of exposure to a larvicide, rinse the eyes with tap water for 20 minutes and wash the skin thoroughly with soap and water. If the symptoms persist, first contact your local doctor or emergency department, then contact the New York City Poison Control Center.

For more specific information on the larvicides Altosid, Vectobac and Vectolex, or other pesticide use, you can call the New York City Poison Control Center at (212) POISONS or (212) 764-7667. For more information about West Nile virus, call the New York City Department of Health West Nile Information Line, 24 hours a day, seven days a week, at (877) WNV-4NYC or (877) 968-4692.

April 2000
Every effort has been made to provide correct, complete and up-to-date pest management information for New York State in this publication. Changes in pesticide regulations thus occur constantly, and human errors are still possible. These recommendations are not a substitute for pesticide labeling. None of the above has been verified by the employees of Ocean-Beach.com

 Revised: 01/14/2004