Leavenworth Mosquito Control District



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History of the Leavenworth Mosquito Control District

Prior to the formation of the Leavenworth Mosquito Control District the Lions Club of Leavenworth had undertaken over a number of years to raise funds for the aerial spraying of mosquitoes in the Leavenworth area.  This spraying typically occurred shortly before the Fourth of July.  However in the late 90's this practice began to be challenged and spraying was suspended in 2000 and 2001.  Mosquito numbers in 2002 were high enough that the City of Leavenworth combined with the Chamber of Commerce took responsiblity for a final aerial spray prior to the formation of the Leavenworth Mosquito Control District.  Funding was provided by the Lions Club.  In the meantime Lions Club members had begun the process of preparing the question of a Mosquito Control District to be put to the voters along with funding for it through taxes.

In the Fall of 2002 voters overwhelmingly approved the formation of a Mosquito Control District and its funding.   Since a board and an approved budget had to be in place prior to the approval of tax collection, no taxes were available for 2003.  The Lions Club generously donated about $20,000 in funds which they had collected for mosquito control.  This along with a small loan obtained in late 2003 financed the initial season of operation.  In 2004 through 2006 taxes were assessed based on property value.  In 2006 the state informed the district that to continue such an assessment a levy must be approved each year. The board therefore decided to collect taxes on a per parcel basis.

After the District was approved by the voters the Chelan County Board of Commissioners accepted applications for the initial Mosquito Control Board and appointed 4 board members: these were  Tom Guthrie, Dayle Massey, Karl Pflugrath and Bill Luebke.  A fifth Veronica Harrison was appointed by the city.  President Tom Guthrie and Secretary Treasurer Dayle Massey were the original board officers.   Dayle Massey is the only continuously serving member from the original board. He now serves as the Board President. Tom Guthrie stepped down for a few years due to illness.  Other obligations or poor health resulted in the transition of the other 3 members.  Bill Luebke was the first to resign followed by Veronica Harrison and Karl Pflugrath. Becki Subido was the first new member.  Later she resigned.  The city appointees have seen the most transition: Veronica Harrison was replaced by Ken Coffin who was in turn replaced by Bob Kelly.  When Bob Kelly resigned, county appointee Larry Meyer took his place and Tom Guthrie returned to take Larry Meyer's place as a county appointee. When Tom Guthrie orriginally resigned Dayle Massey stepped up to become president and Chester Marler joined the board to serve as Secretary Treasurer. Larry Meyer and Nick Stemm are regular board members.  All board members have served at least 5 years (at least 2.5 two year terms). People interested in serving as board members are invited to contact Manager Jenny Mullins at 509-548-5904 and attend board meetings.

The board began meeting in early 2003 and soon became persuaded that the District activities should include larvaciding. A number of Mosquito Control Districts were consulted.  Manager Lorna Johnson of the Curlew Mosquito Control District was especially helpful and agreed to provide some instruction and materials (forms and applicatiors) for the new District.

The position of Manager was advertised and Manager Jenny Mullins was hired to begin May 1st .  She took the information which the Board had gathered and quickly obtained a permit and materials (including the larvicides Bacillus thuringiensis and monomolecular film).  She began the treatment of larval habitat as she searched for such sites by soliciting information from the public as well as by scouting areas by truck and on foot.  Later in the summer Central Washington Helicopters provided a tour of the District and this resulted in the discovery of two ponds and an untreated swimming pool.  In later years, complaints have been used to eliminate backyard breeding areas as well as to pinpoint new treatment sites. 

Large concentrations of Aedes vexans in 2003 and 2006 resulted in aerial spraying of the adulticide malathion.  In 2006 a concentration against the hillside east of East Leavenworth Road resulted in the spraying of 275 acres.  In 2003 most of the district (except for the northern most end) was sprayed in late June.  Complaints continued and the area between Shore Street and the southern end of East Leavenworth Road was aerially sprayed again in late July following a ground spray behind Alpine Heights in early July. 

In 2004 Assistant David Wood was hired.  He worked for us from 2004 thru 2006.  In 2007 Assistant Bruce Hill was hired and provided the majority of larvaciding assistance.  In 2010 he retired and was replaced by Barry Moats who served through 2012 with additional help in the big snowpack years of 2011 and 2012.  Arnica Briody took his place in 2013 and 2014.  
2015 had such a low snowpack (like 2005) that no assistant was needed. In 2016 Teri Sessions joined the District as an assistant: she has served continuously since then. These assistants have been an integral part of our success over the years, since water levels in May and June result in a much greater area of larval habitat.  They each have their own pesticide applicators license and work independently in their assigned areas using their own vehicle.  

In 2004 the treatment of storm drain catch basins began. The introduction to the district of an economical long lasting material Bacillus sphaericus helped to spread out the larvaciding work schedule.  Bacillus thuringiensis israelensis (Bti) continued to be the treatment of choice but in 2006 the use of methoprene was also adopted.  It became clear in 2006 that Bacillus sphaericus was not effective against Aedes vexans.  Fortunately this discovery was made while there was still enough time to retreat the areas with Bti.

Lower water levels in 2004, 2005 and 2015 (record lows in 2005 and 2015) combined with the knowledge of sites gathered in 2003 to produce successful larvaciding years where no adulticiding was necessary.  These years also had early high temperatures so that larvaciding began by April 1st.  In 2006 and 2007 larvaciding was not needed until late April, but more recently larviciding has begun by early April.  Although water levels were much higher in 2006 with flooding in the parks, control of  mosquitoes along the rivers was quite successful.  The missed larva were due to high rains and runoff against the East Leavenworth hillside.  In 2008, 2011 and 2012 high snowpacks also led to high runoff but adequate control was achieved through larviciding.

In 2007 water levels were comparable to that of 2003.  Successful control was achieved.  Almost all sites had trap counts below ten.  However trap numbers at Waterfront Park and the Wheeler Woodland climbed in August to over 20 and 30 Culex per night.  The approach of West Nile virus means that we cannot afford to become complacent.  We seek to improve our control efforts as long as mosquito-borne disease remains a serious threat to our community.  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.

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.  

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.  

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.  Very high water in May resulted in a more nuisance mosquitoes, but there were relatively few complaints.