Leavenworth Mosquito District

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  Local mosquito genera:
 
  • Culex (Culex pipiens and Culex tarsalis)
  • Aedes
  • Anapheles 
  • Coquillettidia
  • Culiseta
 Chemicals and Procedures used:

Larvicides:
  • Bacillus thuringiensis israelensis (Bti) in the form of Vectobac granules and Bti briquettes
  • Bacillus sphaericus (Bs) is used in combination with Bti above in the form of Vectomax granules which have organic certification. 
  • Methoprene in the form of Altosid pellets for long-lasting control of all mosquito larva
  • Spinosad in the form of Natular could be used but will not be (due to broad spectrum effects) as long as the above 3 (or pupicides) are effective
 Pupicides:
  •  Cocobear, a paraffinic mineral oil used to kill pupa
  • Agnique MMF, a monomolecular film (note: used through 2020 to kill pupa but is no longer available)
 
Last Resort pesticides for Adult Mosquito control:
  • Board approval is required
  • Notice will be provided to the public prior to use
    • Malathion used to kill adult mosquitoes (last used in 2006 aerially)
    • Alternatives to malathion which could be used are: natural pyrethrins, piperonyl butoxide (PBO), permethrin, etofenprox, naled, prallethrin, resmethrin and/or sumithrin
 

 

2020: Nuisance mosquitoes caused several complaints south of Prowell Road.  Culex mosquito numbers continued below 10 until the very end of August when 24 were caught at Waterfront Park. There were also enough (at least 10) to test for West Nile virus one time in early September.  All mosquitoes tested negative for the disease.

 

 

2019: Snow pack levels were below normal and excellent mosquito control was obtained throughout the season. This was the 3rd year in a row that Culex numbers were kept so low that testing for West Nile virus was unnecessary.  Fewer than 10 Culex were caught per night in each trap.


 

2018 was also a very good year for successful control of Culex mosquitoes: no more than 8 Culex mosquitoes were caught in a trap: this was the first time that West Nile virus testing was not required for two years in a row. High water levels in May resulted in a more nuisance mosquitoes, but there were relatively few complaints.

 

 

2017 was the first year we conducted aerial larviciding by helicopter.  This was done on April 10 and May 2 to 20 acres against the East Leavenworth hill side just east of 1.5 miles to 1.9 miles along the East Leavenworth Road.  This snowmelt wetland was the source of the adult mosquito problem in 2006 and was particularly large and deep this year (and much too brushy to use a boat) . The same granules we spread by hand (Vectobac: Bti) was spread by helicopter.  Very few adult mosquitoes were found there over the summer so the aerial larviciding was successful.  

2017 was a very good year for successful control of Culex mosquitoes. The previous year there had been enough to test for West Nile virus at Prowell, Run of the River and the Wheeler woodland.  In 2017 all these areas along with Mine Pond were treated with Vectomax (a Bti, Bs combo) by June or July since it provides better control than Bti alone in wetlands with high organic matter.    No more than 5 Culex were caught at any location overnight so West Nile virus testing was not needed.  This is similar to the degree of success achieved in 2010 and 2013 when testing was also not needed.  There were enough Aedes to generate a few complaints in some areas especially Prowell where up to 32 were caught, but this was still well below the minimum of 70 required for spraying of nuisance adult mosquitoes.  

 


In June 2016 the Prowell Road area once again has an elevated number of Culex mosquitoes.  West Nile virus testing on June 10 showed Ramp readings of 54 and 32 for Culex pipiens mosquitoes collected from two traps in the area.  This was the only time readings were over 10.  RAMP testing was begun in 2014 since VecTest was no longer available.  

 


2015 had high numbers of Culex by the Mine Pond snowmelt pond.  We continue to pay close attention to each area with regular trapping during the season.  It is believed that Bti was bound up by the organic matter at Mine Pond so Bacillus sphaericus (Bs) will be tried there from 2016 on starting in late June.

 

 

2010-2015: In 2010  excellent control was achieved with a high trap count of just 12 mosquitoes and fewer than 10 Culex per trap.  These numbers were further reduced in 2013 with a high trap count of just 6 mosquitoes.  In 2012 the numbers of Culex between Prowell and East Leavenworth road were a source of concern, peaking at 39.  2014 saw high numbers of Aedes against the East Leavenworth hillside and south of Shore Street while 2015 had high numbers  of Culex by the Mine Pond snowmelt pond.  We continue to pay close attention to each area with regular trapping during the season.  It is believed that Bti was bound up by the organic matter at Mine Pond so Bacillus sphaericus (Bs) will be tried there from 2016 on starting in late June