Pest Management  - Chemicals & Other Techniques

Chemicals should be used as a last resort when trying to eliminate mosquitoes. Your first steps should be: If you still find an overabundance of mosquitoes then you can see if one of the methods below is appropriate.


Mosquito Dunks and Bits

Bti Larvicide (a.k.a. Mosquito Dunks and Bits) kill mosquito larvae. It can be purchased in home improvement stores and online. Bti larvicide should only be used in standing water in containers on your property that do not drain to open waterways, storm drains, ponds or wetlands. The scientific name for Bti is Bacillus thuringiensis var. israelenis.

Bti larvicide kills other aquatic insects in addition to mosquito larvae, therefore they should not be used in water that flows into natural water bodies.

Appropriate Places for Mosquito Dunks:
  • Flower pots
  • Bird baths
  • Roof gutters
  • Rain barrels
  • Old tires (For tire swings, drill holes in the bottom to allow for draining!)
  • Swimming pools
  • Ornamental ponds, such as fish ponds. (They are NOT for stormwater management ponds)
  • Animal watering troughs

DO NOT Use Mosquito Dunks In These Locations:
  • Water that drains to natural water bodies, such as creeks, streams
  • Water that is moving (mosquitoes can't breed in moving water)
  • Ponds, lakes, stormwater ponds or wetlands
  • Any water on parkland.  

VectoLex (Bacillus sphaericus or Bs) is another bacterial larvicide that does a better job targeting mosquito larvae over other aquatic insects, but can only be purchased and applied by someone with a pesticide applicator license.  The Bs larvicide is an option for MDA and other public agencies to treat natural water bodies when necessary.


FAQs on Mosquito Dunks



Should you choose to hire a contractor to spray around your home to deter mosquitoes, you should make sure the company is licensed to apply pesticides in Maryland.   The Maryland Department of Agriculture (MDA) is the licensing body and they have a web tool where you can enter a name of a company to find out if they are licensed.

Broader-scale spraying of adulticides may be performed by MDA or other public agency when other controls are not possible or are not effective in reducing mosquitoes below a level that may cause unacceptable annoyance or a public health threat.  

  • Adulticides only kill flying adults and not mosquito eggs or larvae.  
  • Many adulticides are also toxic to other flying insects, including beneficial bees and butterflies.  
  • When adulticides are carefully applied according to the label, environmental and human health effects can be minimized but not eliminated.  
  • The EPA provides additional information about pesticides used to control adult mosquitoes.‚Äč