The Grand Forks Mosquito Control Program received overwhelming approval during a City of Grand Forks ballot measure on November 7, 1996. The citizens voted 91.8% to continue a mosquito control program implemented as a two year pilot test during 1995 and 1996. The program is designed to promote health and well being by reducing the risk of mosquito-borne diseases and reducing the nuisance level of mosquitoes in an environmentally sensitive manner.
The mosquito problem in Grand Forks is primarily generated by two types of mosquitoes, the floodwater (Aedes/Ocherotatus) and standing water (Culex) mosquitoes. The plan to control these insects is based on an understanding of their life cycle, reproductive cycle, habitat, and range of travel. A comprehensive mosquito control program employs all phases of mosquito control, such as source reduction, surveillance, larviciding, adulticiding (ground spraying), and public education.
The Aedes/Ochlerotatus mosquitoes lay their eggs on the ground in areas that are eventually covered with water at a later time. The eggs need water to hatch into larvae and to continue their life cycle. The mosquito remains in the larval stage for several days (3 – 10 days on average, depending on temperature and species) before transforming into the pupae stage. The pupae stage is a resting stage for the mosquito before it transforms into an adult. Once the eggs hatch, the cycle from egg to adult takes about seven to fourteen days in the Grand Forks area. The time it takes for the mosquito to complete its life-cycle depends on the average temperature and species. The adult female mosquito mates almost immediately and then seeks a blood meal to nourish the eggs before laying additional eggs. The life cycle then begins again. Mosquito eggs can lie dormant for several years before receiving enough water to hatch. The female floodwater mosquito has an effective range of five to ten miles, but may travel as far as forty miles to obtain a blood meal.
The Culex mosquito, specifically the Culex tarsalis, has significance not only as a nuisance, but also as a potential carrier of the West Nile virus, St. Louis Encephalitis, and Western Equine Encephalitis, which can be deadly to humans.
The Culex mosquito lays her eggs in standing water. The habitats generally preferred are open, sunny areas, but shaded areas with vegetation are also used. The Culex mosquito is also a container-breeding mosquito. Containers as small as a bottle cap may be successful in producing mosquitoes. The egg to adult life cycle can be completed in seven to 10 days, dependent on the weather. The adult female mosquito may live approximately four to six weeks. During this time seeking many blood meals and potentially laying thousands of eggs. The Culex mosquito can travel several miles from a breeding site, but generally stays close to its origin.
The policy for adulticiding (spraying, fogging, etc.) in Grand Forks is determined by the surveillance division through several factors. Thresholds have been established based upon surveillance and monitoring efforts for immature and adult mosquito populations using several types of indicators. No one factor is always decisive for determining action. Often times a combination of quantitative or objective data must be evaluated to make “spray/ no-spray” decisions. Some of the factors considered prior to citywide spraying include; mosquito population, species diversity, mosquito-borne disease activity, community events, specific (public) events, weather conditions (short term and future weather conditions) and environmental factors. The numeric values for the thresholds are subject to further refinement or modifications by the Mosquito Control Surveillance Division as circumstances or new information warrants. As a result of the information gathered, a responsible decision can be made as to the timing and justification of a ground spray effort. Without this information and guidelines, inappropriate spraying of pesticide throughout the city might occur. This option contains a measuring device that is essential to any mosquito control program.
The public education program includes presentations, newsletters, TV commercials, radio, newspaper, etc.
The use of any type of insecticide may pose a certain amount of risk to the the public and the environment. The insecticides used by Grand Forks Mosquito Control are cost effective and environmentally sound products which minimize the risk to the public and environment. The intent of this program is to reduce the mosquito population without harming people or the environment. While the Environmental Protection Agency considers the chemicals used in ground spraying safe for use as intended, we recommend people avoid direct contact with the spray. Our staff are instructed to shut the sprayer off if they suspect there’s a possibility of the spray coming in contact with people.
The type of products used in the ground spraying operations are synthetic pyrethroids. These products are toxic to adult mosquitoes. Proper education and training help minimize the risk to the public and environment when using public health pesticides.