The Town of Johnstown’s Environmental Mosquito Management Program

In 2011, The Town of Johnstown Mosquito Management Program completed its 8th year of cost effective Integrated Mosquito Management operations with Colorado Mosquito Control (CMC) as its contractor. Mosquitoes are dynamic insects which are capable of rapid populations increases dependent on habitat, water level, rainfall events, and temperature patterns.  The experience and knowledge possessed by CMC employees of the local lands and irrigation patterns, enables an overall reduction of mosquitoes.  The biorational management operations and data driven response to spikes in mosquito abundance are aimed at reducing the risk and annoyances associated with mosquitoes.  If left unmanaged residents residing throughout large sections of the town would be burdened by mosquitoes, thereby resulting in a decreased quality of life and reduced ability to enjoy outdoor activities.

The primary objective of the Johnstown Mosquito Management Program is to employ trained field biologists to suppress the development of larval mosquitoes in the aquatic habitats.  CMC prioritizes, at minimum 90% of resource allocation on larval control efforts. Surveillance monitoring of adult mosquito populations is performed to determine the need to reduce adult populations via adulticiding materials. This goal enables a reduction in both the overall mosquito populations and the threat of mosquito borne disease transmission at the least possible cost, while minimizing the impact on the people and natural environment.

Please call 970-962-2583 or 970-663-5697 to report any water that stands for more than 4 days, mosquito annoyance concerns, or for information regarding West Nile Virus prevention.

The larval coverage area includes approximately 7.2 square miles of private and public lands, where resident contact has been made and permission has been granted in the town limits of Johnstown. 

Johnstown’s Integrated Mosquito Management program focuses on utilizing naturally occurring soil bacteria, larvicides, to control mosquitoes in the larval stage, instead of relying entirely on application of pesticides in the form of fogging materials.  The program primarily utilizes applications of Bti, a stomach toxin, which is target-specific to larval mosquitoes. This naturally occurring bacteria is activated by a specific pH within the larval gut and disrupts the larvae’s ability to consume and digest food resources.   
When properly carried out, by trained applicators, IPM programs return beneficial results in reduced pesticide use, reduced frequency of pesticide resistance, and reduced exposure to pesticides by the environment. The Mosquito Management Program offered by CMC follows successful IPM principles for cost effective, scientific methods of survey/inspection, evaluation, diagnosis, application and record keeping of materials used.
To date, there are 124 active larval mosquito habitats and 36 mandatory sites (weekly or twice/week inspections based on seasonal potential) included in the inspection and larviciding program for Johnstown. Field technicians methodically inspect larval habitats twice a week, weekly, bi-weekly or post rainfall, as deemed necessary based off of historical data.  A technician may spend the day inspecting a variety of habitats ranging from urban mosquito breeding locations (storm drains, catch basins, wading pools, paddle boats & tire piles), as well as cattail marshes, stagnant ditches, reservoir edges and irrigated pastures.  Inspections are performed to determine whether larval mosquitoes are present or not at a site. Once the presence of mosquito larvae is confirmed, larvicides are applied.  This enables targeted control, while reducing the miles of city streets that need to be fogged for adult mosquitoes.

The 2011 mosquito season can climatically best be summarized as warm and wet.

April ended warmer and drier than normal according to the National Climatic Data Center (NCDC), while May finished cooler and wetter.  June’s mean temperature of 68.2oF for the Denver area was only 0.6oF above normal (68.8oF). A total of 2.43 inches of precipitation fell during June in the Denver area which was 0.87 inches above average. In addition to above average rainfall, above average snowpack for many of the rivers across the Northern Front Range presented record runoff levels during June and into July.

July marked the third month in a row in which precipitation was above normal, with 3.41 inches of rain recorded in the Denver area.  This was 1.25 inches above the average for this month. Most of that moisture fell in the first weeks of the month which, along with the heat that followed, resulted in an increase of both larval and adult mosquito activity. The average temperature for July was 73.4oF according to the NCDC, which was 2.5oF warmer than normal. July contained twenty days in which temperatures exceeded 90oF.  Seventeen of those twenty days occurred during a consecutive period of July 15th - July 31st.

The combination of heavy rains during the first part of July followed by weeks of temperatures in the 90s resulted in a subsequent spike in flood water mosquitoes and customer concerns. Severe weather often impeded both larval and adult control operations as omnipresent standing water presented seemingly countless new potential breeding sites.  Evening fogging applications were often also delayed or rescheduled due to high winds and heavy rain.

Temperatures in August broke records as it became the hottest August since 1872. There were twenty-two 90 plus degree days in August.  By August 31st there were seventy-one consecutive days with high temperatures reaching or surpassing 80oF, which broke the record of fifty-nine days set in 2002. A total of 0.3 inches of rain fell during August in the Denver area, which was 1.27 inches below average (1.57”), according to the NCDC.

The heat wave and dry conditions in August caused water levels to recede at many larval sites. This greatly reduced the amount of mosquitoes collected in light traps, compared to July.  This helped bring workloads back to normal levels, as compared to the fast paced operations required in July.  Fortunately, the overall numbers of Culex mosquitoes remained below epidemic levels as a result of fluctuations in water levels for a majority of the 2011 season. 

Information about mosquito abundance and species identity is critical to a successful mosquito control program.  Colorado Mosquito Control employs two kinds of traps to monitor mosquito populations.  The most commonly used is the CDC light trap which  uses carbon-dioxide from dry ice as bait to attract female mosquitoes seeking a blood meal from a breathing animal.  Once attracted by the CO2, the mosquitoes are lured by a small light to a fan that pulls them into a net for collection.  The Gravid Trap uses a tub of highly-organic water as bait to attract female mosquitoes that are looking for a place to lay their eggs.  A fan placed close to the water surface forces mosquitoes that come to the water into a collection net.  Once back in the laboratory, the contents of the trap nets are counted and identified by technicians trained to recognize the Colorado mosquito species.

In 2011, Colorado Mosquito Control monitored a statewide network of hundreds of weekly trap sites, collecting over 900,000 adult mosquitoes that were counted and identified to species by the CMC Surveillance Laboratory.  While individual traps provide only limited information, trap data is interpreted in the context of historical records for the same trap site, going back in time more than a decade.  Individual traps are also compared to other traps from around the region that were set on the same night and therefore exposed to similar weather conditions.  Technicians working in the Surveillance Laboratory at Colorado Mosquito Control, Inc. are trained to provide accurate species-level identification of mosquito specimens, for both adults and larvae.  More than 50 mosquito species are believed to occur in Colorado, and 32 of those were identified from samples processed during the 2011 season from across the state.

Additionally, the CMC Surveillance Laboratory conducts an intensive larval identification program with larval mosquito samples collected by I&L technicians prior to larviciding being identified to species.  This information is now invaluable in targeting mosquito control efforts as we gain a greater understanding of the habitat types preferred by Colorado mosquito species and the seasonality of these habitats as sites for mosquito development. 
CDC Surveillance Light Trap Data Comparison

In 2011, an average of 5 surveillance light trap locations monitored adult mosquito populations within Johnstown. The surveillance locations for Johnstown included: (JT-01) Johnstown South Pioneer Ridge, (JT-03) Johnstown Central at Rolling Hills Ranch, (JT-04) Johnstown West at Rocksberry Ridge, (JT-05) Johnstown East at 237 East 2nd and (JT-06) Thompson River Ranch. CMC relocated the South Pioneer Ridge location on July 26th to its new permanent location on Mallard Drive in Pioneer Ridge (JT-07). Surveillance trapping began June 1st and trapping was concluded on September 1st in all areas halted by cooler temperatures during the first weeks of September.  

In 2011, 75 surveillance light traps were set within Johnstown which collected 29,016 total mosquitoes. The average number of mosquitoes collected per trap per night was 387 and the average number of Culex spp. mosquitoes collected per trap per night was 12. The percent composition of mosquitoes collected in 2011 included; 80.9% (23,466) Aedes/Ochlerotatus spp., 5,112 (17.6%) Culex tarsalis, 219 (.8%), Culex salinarius, 104 (.4%) Culex pipiens, and 115 (.4%) Culiseta spp. mosquitoes. The 2011 season set new records for annoyance mosquito collections and associated reports.

Targeted Ultra-low Volume Adult Mosquito Control

The goal of Colorado Mosquito Control, Inc. is to provide all residents of Johnstown with the best options for safe, effective, modern mosquito management. The primary emphasis of our mosquito management program is to control mosquitoes in the larval stage, using safe biological control products.  This environmentally focused program maintains adulticiding applications as a final resort when mosquito populations surpass nuisance or risk thresholds. Mosquito surveillance trapping results are used to make data-driven decisions regarding areas that need to be sprayed for adult mosquito control. Adult mosquito control spraying is targeted to specific sectors determined by this trap data, thereby reducing the area sprayed and the frequency of spraying in each sector. 
CMC uses all available data from CDC light traps, gravid traps, Mosquito Hotline annoyance calls, and field technician reports to focus adult mosquito control efforts on specific, very limited “targeted” areas. 

CMC uses state of the art technology, calibrated application timing, and least-toxic products to minimize non-target impacts.  All adult mosquito control is accomplished using Ultra Low Volume (ULV) fogging equipment and performed after dusk when the majority of mosquito species are most active.  This type of equipment produces droplets averaging 12 microns in diameter and allows for a minimal amount of product to be put into the environment. These treatments take place in the evening when mosquitoes are flying in greater numbers and non-target insect activity (for example, day-flying pollinators like bees) is greatly reduced.  Using this application technique, the overall goal of minimal environmental impact and effective adult control is achieved in the targeted area.

In 2011 CMC utilized the water-based products AquaLuer 20-20 and Envion for ULV adult mosquito control.  Both use the highly effective pyrethroid Permethrin as their active ingredient, while the water-base provides a much more environmentally sound solution to traditional petroleum oil-based adulticides.

Notification and Shutoff Services
Upon request, residents can be notified prior to spraying with Permethrin insecticides.  Call & Shutoff forms are available online and may be submitted via CMC website or by mail. Please note that a shutoff does not guarantee that drift of insecticide material will not occur and may decrease the effectiveness of adulticiding on mosquitoes in your immediate area. Please note that the call shutoff list is a service that CMC provides to residents and may be obsolete in the case of a West Nile Virus Public Health emergency, as experienced in 2003/ 2007.  For additional information regarding permethrin, including toxicology data please visit: www.comosquitocontrol.com and click on the tab for pesticides.