The Town of Johnstown’s Environmental Mosquito Management Program
The Johnstown Mosquito Management Program can provide services regarding:
• Information about mosquito biology and source reduction of mosquito habitats
• Information on mosquito control and monitoring efforts within the city and West Nile Virus activity on a seasonal basis
• Information about personal protection for mosquito annoyance and West Nile Virus risk
• Arrange routine habitat inspections at residential backyards, catch basins, retention ponds on either city or private property with permission
• Perform application of mosquito control products using integrated pest management methods and target specific controls on mosquito larva at no cost to the property owner
• Discuss treatment options and management procedures with property owners
• Respond to reports and concerns of mosquitoes and possible mosquito habitats
• Stock residential ponds with fat head minnows for biological control
In 2009, The Johnstown Mosquito Management Program completed its 6th 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 of CMC and its’ 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.
Colorado Mosquito Control has designed, implemented, pioneered, refined and pushed to new technological levels, a comprehensive mosquito control program based on the sound scientific principles of IPM and the environmental goals of Johnstown. In the years since the Johnstown’s inception and continuation of CMC as the program contractor, the Mosquito Management Program, under the operation and management of CMC, has developed into one of the foremost environmentally sensitive and technologically advanced Integrated Mosquito Management Programs in the United States.
The objective for the Johnstown Mosquito Management Program is to utilize trained field biologists to suppress the number of mosquitoes, in the aquatic larval habitats. This reduces the potential for mosquitoes to emerge from the water to feed on and possibly infect the residents of Johnstown. Johnstown monitors adult mosquito populations via a surveillance trapping network to enable a proactive response to suppress West Nile Virus vector mosquito populations prior to a public health emergency outbreak. Adult mosquito population data provides real time information regarding the nuisance and risk associated with mosquito populations within Johnstown. This data provides scientific premise when determining the need to reduce the mosquito populations via adult mosquito control materials.
This objective enables a decline in the overall mosquito populations, while reducing the threat of mosquito borne disease transmission, at the least possible cost, and with the least possible impact on the people and natural environment. CMC will continue to strive and demonstrate a commitment to Integrated Pest Management principles for a progressive approach to mosquito reduction.
The larval coverage area includes approximately 7.2 square miles of private and public lands, where permission is granted, within town limits of Johnstown. Although many of the larval mosquito habitats are outside the town limits, all are well within the flight range of most mosquitoes. Larval control work within and around the town boundaries will continue to remain a critical part of the overall operation of CMC. Studies have indicated that adult mosquitoes can travel several miles in search of a blood meal and new habitat for offspring. CMC’s larval mosquito reduction across the control area greatly reduces transient mosquito populations.
Funding for the Johnstown Mosquito Management Program is appropriated from a general fund from local tax revenue. The money paid funds the surveillance monitoring of larval mosquitoes in the water, the application of bio-larvicide control products, the monitoring of adult mosquito populations via mosquito traps throughout the town, and data driven response & control of adult mosquitoes through ULV fogging applications.
The History behind the Johnstown’s Mosquito Management Program
After 6 years of larval control in the Johnstown and buffer areas, the reduction in overall mosquitoes is evident from surveillance data and resident feedback, despite seasonal variation in temperature and rain variables. This environmentally friendly program always uses biological control choices first to reduce mosquito populations at the source…the aquatic larval habitats. Larvicide applications are designed to reduce mosquito populations below established disease thresholds.
The Town’s Integrated Pest Management program focuses on utilizing naturally occurring soil bacteria, larvicides, to control mosquitoes in the larval stage, instead of solely 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.
2009 Season Perspective
The higher-than-normal levels of precipitation during the 2009 season replenished the water table to levels not seen in years for many areas along the Front Range. Rainfall totals remained above average for a majority of the 2009 mosquito season. Although most of the rainfall occurred in early April and June, additional weekly rainfall created numerous larval mosquito habitats and kept things green throughout the season. With the excess moisture came a corresponding above-average workload for larval mosquito control activities, due to the flushing and refilling of aquatic habitats on a regular basis. In general, many reservoirs and ditches remained full for a large portion of the summer, because irrigation water was not moved as quickly. Many grassy edges and inlets to reservoirs were consistently producing mosquito larvae throughout most of the season. Working with local farmers to understand and recognize the patterns of agricultural irrigation continues to be one of CMC’s ongoing priorities.
Mosquito populations in the first part of the 2009 season consisted of primarily Aedes spp., known as “floodwater” mosquitoes as their eggs hatch in response to rising water levels resulting from rainfall and/or irrigation. Adult Culex mosquito populations spiked in mid-July, as they require standing water to lay their eggs in. Overall, vector mosquitoes comprised about 50-75% of mosquito collections during July and August, remaining in line with historical averages. This scenario could have played out much differently had the median temperature during early spring been warmer, as occurred in 2003 when the vector Culex mosquitoes had an early population spike. 2009 was different in that we had similar moisture levels, but without the corresponding high temperatures of the 2003 “WNV epidemic” season.
In 2009, 81.4% of total site inspections consisted of wet sites with larval production at 48.3% of those sites. An estimated 351.6 million larvae were eliminated before emerging due to larval control operations in 2009. The first West Nile Virus infected mosquitoes were detected in Weld County on July 10, Boulder County on July 13, and Larimer County on July 14. West Nile infection rates in mosquitoes remained below epidemic years and the Colorado Department of Health and Environment (CDPHE) ceased WN testing of mosquitoes on August 14. Dip counts for larval mosquitoes slowed into late August. By the first days of September the species composition of Culex mosquitoes collected from adult trapping dropped to less than 10% of the total counts in most areas. In 2008, the Northern Front Range did not receive heavy rains in May, June or July, thereby keeping floodwater mosquito species below normal in some areas. Exceptions to this occurred in areas that saw heavy flood irrigation or spring snow melt runoff along the river basins of the Big Thompson and Poudre River. Most of the significant mosquito populations early in the season were Aedes species resulting from river runoff and early season irrigation. Lab larval identification of mosquito samples collected during field inspections indicated an increase in Culex tarsalis mosquito larva during week 26 (late June) and another spike in the second week of July (week 28).
Targeted Ultra-low Volume Adult Mosquito Control
Adult mosquitoes can come from unknown unidentified sites or may migrate in from uncontrolled areas. The Johnstown uses all available data from CDC light traps, Mosquito Hotline annoyance calls, and field technician reports to focus adult mosquito control efforts on specific, very limited “targeted” areas. In parts of the community were high numbers of mosquito annoyance calls are received, “floater” CDC light traps are set to evaluate adult population levels and species make-up. In most cases, a direct correlation is evident between areas with high complaint calls and high trap counts. While this correlation allows us to focus adult control in these areas, the emphasis is placed on finding the source of breeding and continued larval control measures. Over 95% of the Johnstown mosquito control program is targeted against larval (aquatic stage) mosquitoes utilizing biological control materials, however on occasion adult mosquito suppression becomes necessary. If deemed necessary from surveillance trapping data, Colorado Mosquito Control utilizes 3.3% Permethrin in ultra low volume (ULV) spray applications via truck mounted fogging machines. ULV sprayers dispense an extremely small amount (0.0019 pounds per acre) of fine aerosol droplets which stay aloft and kill adult mosquitoes on contact. Permethrin is a synthetic pyrethroid similar to the insecticide pyrethrum which occurs naturally in chrysanthemum plants. Permethrin is found in a variety of products, including household insecticides, flea dips, repellent for clothing, sprays for pets, and lice shampoos. This pesticide has been selected to achieve effective control of mosquitoes and suppression of West Nile Virus transmission with the least impact on human health and the environment. Fogging applications are performed only within the first few hours after sunset because this is the most active period for mosquitoes, when they emerge from the vegetation after the hottest part of the day has passed. All insecticides used by Colorado Mosquito Control are registered by the EPA and the Colorado State Department of Agriculture. Fogging applications are performed based on mosquito populations caught in traps on a nightly basis. Specific neighborhoods are fogged when surveillance traps catch 100 floodwater mosquitoes, referred to as a “Nuisance Threshold” or 50 Culex mosquitoes, referred to as a “Disease Threshold”. The thresholds for fogging applications are established by an industry standard that measures vector and nuisance mosquito populations. Colorado Mosquito Control uses state of the art technology, correct application timing, and least-toxic products to minimize non-target impacts. All adult mosquito control is accomplished using calibrated Ultra Low Volume (ULV) equipment and performed after dusk. 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 activity is greatly reduced. Using this application technique, the overall goal of minimal environmental impact and effective adult control is achieved in the targeted area. All insecticides used by Colorado Mosquito Control are registered by the EPA and the Colorado State Department of Agriculture.