North Shore Mosquito Abatement District
Larviciding Program

Larviciding is aimed at controlling
mosquito larvae at the source of
reproduction where it is most
concentrated and vulnerable.  
Approximately 80-90% of the
Districts field program is directed
toward controlling mosquito
larvae in an average season, thus
larviciding is the major
operational program of the
District.  In 2003, larviciding
accounted for approximately
90% of our field program. We
treated approximately 4376 sites
and over 42,000 catchbasins.  

NSMAD's Chief Inspector James Binnall:
Treating some Standing Water in District.....z1980

When larviciding, the District uses
pellets and briquettes containing
methoprene (an insect
growth-regulator that is similar to
that found naturally in mosquito
larvae) as the primary means of
control used to treat small enclosures
of water such as poorly-maintained
ornamental ponds, abandoned
swimming pools, and catch basins.  
These breeding hotspots continuously
produce Culex mosquitoes. and once
in the water, These chemical
briquettes, when placed in these
breeding sites, slowly release
methoprene into the water and
prevent mosquito larvae from

NSMAD's Chief Inspector James Binnall:
Collecting a Dipper Sample in District.....z2005

developing past the pupae stage. It is a mosquito specific treatment; therefore other
organisms in the environment (such as insects, waterfowl, and mammals) do not suffer
deleterious effects.  In 2003,the NSMAD applied approximately 991 lbs. Throughout the
District.     
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          The N.S.M.A.D. also uses two types of widely used bacterial larvicides. These larvicides
are mosquito specific and are safe to humans and other mammals.  In order to treat small
marshes and catch basins, the district applied Bacillus thuringiensis var. Israelensis (BTI).  BTI,
used in either granular, liquid, or briquette formulations, is spread over flooded land or in
depressions that periodically flood or in catch basins that are not completely flushed after a
heavy rain .

                  The District also uses Bacillus sphaericus (B.s.). B.s. is similar to BTI in respect to its
mosquito specificity and ability to be used in wastewater, drainage systems, tire dumps, rice
fields, coastal areas, and natural or manmade aquatic sites.  However, in contrast to BTI, B.s.
can be applied in stagnant and polluted water-areas where the encephalitis transmitting
Culex sp. breeds. Overall, in 2003, the NSMAD applied approximately 5006 lbs. of B.s.
throughout the District.  

                                                     Swampy lowland areas, new construction sites, ditches along
roadways and railroad right-of-way, flooded yards, storm sewers, and other small temporary
impoundments of water were all potential sources of mosquito reproduction when water
was stangnant for approximately 6-10 days without treatment.  Fishponds and ornamental
pools were also inspected periodically for the presence of mosquito larvae.  Treatment of
these mosquito-breeding sites is the primary objective of the larviciding program. The
inspection of these areas continues throughout the summer on a weekly basis.