Integrated Pest Management
The Cape Cod Mosquito Control Project (C.C.M.C.P.) was organized in 1928. Since its organization the C.C.M.C.P. has tried to use the most effective, yet least environmentally invasive mosquito control techniques. The control plan follows the fundamental concepts described by the phrase Integrated Pest Management. Integrated pest management (IPM) simply stated is the combination of mechanical, cultural, and biological controls to keep pest populations low enough to prevent intolerable damage or annoyance. While the C.C.M.C.P. has utilized this concept from its inception, we feel it is important to put our current policy into writing.
Any IPM program is composed of the following four basic components:
- pest threshold
As the C.C.M.C.P. concentrates on controlling mosquitoes in their immature stages, the IPM policy will only deal with the control of mosquitoes in their larval and pupal stages.
Inspection is the first step toward solving a pest problem. The inspection can take various forms. During the mosquito season, on a daily basis, crews from the C.C.M.C.P. conduct larval surveys. This means that all sites that have been known to contain mosquitoes in the past are checked for the presence of mosquito larvae. This is accomplished through the use of a standard dipper (350 ml). Other methods of direct inspection include searching for new larval habitats (i.e. artificial containers) and developing mosquito habitats (i.e. water that has been blocked from running). Landing rates of adult mosquitoes are also noted. Further, light traps are placed at various locations around the county. Mosquitoes are removed from the light traps, counted, and identified. Finally, although it can be subjective, discussing the level of the problem with people in the area can help in a pest inspection.
2.) Pest Threshold
Pest threshold refers to the level at which any increases in the pest population will cause damage or annoyance. That is how many mosquitoes can be tolerated before action is taken to reduce the population. This is a very difficult term to define as it relates to mosquito control. Many factors must be taken into account before determining the pest threshold. Most important is the history of the site. Changes in the species composition and environmental conditions must be taken into consideration. Human population density is another significant factor. The following general threshold levels for treatment are currently being utilized:
- Zero tolerance (i.e. any larvae found are destroyed) is accepted when the area has a high human density, especially areas where children spend time outdoors. Zero tolerance is also accepted when dealing with salt marsh mosquitoes. As salt marsh mosquitoes will fly great distances to find a host and develop very quickly, these mosquito larvae are destroyed immediately without regard to the population size.
- Some tolerance is acceptable in other situations. In areas of low human population density, at least 10 dips are taken. If there are more than 5 mosquito larvae per dip an application is undertaken.
The application of choice is source reduction. Mosquitoes only develop in standing water, so if standing water is reduced or removed so is the mosquito population. Source reduction can be accomplished through a variety of methods. The method used depends on the source of the problem. In cases where artificial containers are concerned (tires, buckets, boats, etc.), education can be the most important method of source reduction. Once people realize where the mosquitoes are coming from they can then keep mosquitoes from developing on their own property. The other methods of source reduction concern the work done to keep water moving. Opening ditches, pipes, culverts, etc. allows water to continue flowing and reduces the habitat in which mosquito larvae develop.
While source reduction is the preferred application choice, there are some circumstances where removing standing water would be impractical. In these cases a larvicide is used. The type of larvicide used to control the mosquitoes will depend upon the developmental stage the insects have reached when discovered. Larvae in the 1-3 instar stages are treated with either Bti ( a bacteria) or in a catch basin environment Bacillus sphaericus in water soluble pouches. Fourth instar mosquito larvae and pupae must be treated using a different method, as the larvicides already mentioned are not able to affect their development at these stages. A light mineral oil is applied in cases where the mosquitoes have developed past the 3 instar stage. Finally, there are circumstances where no application is required. In some cases even though a few mosquito larvae are found, the population does not reach pest threshold. Populations below the pest threshold are not treated.
Monitoring is a major part of any IPM program. Adult mosquitoes are monitored with the use of carbon dioxide light traps. These traps are run once a week. Mosquitoes collected from these traps are taken back to the lab where they are counted and identified to species. Mosquito larvae and pupae are monitored on a regular basis by the field crews. All sites identified as potential mosquito habitat have been logged and recorded in our GIS system. Throughout the mosquito season, sites are checked on two week rotations. Any reapplication or source reduction work is completed or noted for future completion.
Eastern equine encephalitis surveillance has been a part of our program for over 30 years. Mosquitoes are trapped using both light traps and resting boxes. Specimens are identified then transported to the Massachusetts Department of Public Health for testing. In 2000, the C.C.M.C.P. instituted an expanded arbovirus surveillance program to include the trapping of mosquitoes for West Nile Virus (WNV). The C.C.M.C.P. has built CDC type gravid traps that are placed in 14 locations around Barnstable County. This WNV program is a new and continues to expand as we learn more about the nature of the disease.
The above stated IPM program is carried out by the 26 full-time employees of the C.C.M.C.P. The larval surveys and pesticides application are completed by ten, 2 person field crews. Each crew has responsibility for mosquito control in one specific area of Barnstable County. These crews work in the same area year after year. Crew members have spent an average of 10 years in their respective area. In addition to the 20 field crew members the project employs a seasonal employee, carpenter, an administrative assistant / dispatcher, and a field supervisor. Everyone is under the direct supervision of the assistant superintendent and superintendent. Field crews communicate with the administration daily through a two-way radio system run by the admin./dispatcher. The crews call in to the office four times a day. They give their location and a short description of the work they are completing. At the end of each day, the crews call in with a work summary for the day. A weekly report is written and submitted by each crew and entered into our computerized database/GIS.