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Chemical control involves the use of biorational products and insecticides to kill mosquitoes. The products aimed at the immature stages (larvae and pupae) are called larvicides, and products aimed at controlling the adult flying population are called adulticides.
A. Larvicide - This approach is used where practical, so as to reduce the amount of adulticide (See Section V.B. Adulticide ) used. It is typically more effective and target-specific than adulticiding, but less permanent than source reduction. Biorational products (see Glossary) such as Bacillus thuringiensis israeliensis (B.t.i.), Bacillus sphericus, and methoprene (an insect growth regulator) and oils are the products of choice to be used against the mosquito larvae. A list of recommended larvicides and oils is available in The Insect Pest Management Guide published by the Louisiana Cooperative Extension Service of the LSU AgCenter (see complete reference at right under Further References and Websites ).
A list of prospective sites and pertinent facts is as follows:
1. Treatment of roadside ditches - Primarily for the control of the Southern House Mosquito, but also for freshwater species breeding in permanent water and for floodwater species.
a. Ditches are treated by the use of conventional or right-hand-drive vehicles.
b. Granular or liquid formulations are used.
c. Treatments are routinely performed throughout the mosquito season.
d. It is the primary control method of the Southern House Mosquito.
2. Treatment of swales, permanent ponds, storm water retention structures, flood-water pools and depression areas in pastures, vacant lots, wooded areas and flooded rice fields.
a. Aerial ultra low volume (ULV) or low volume (LV) liquid or granular treatments are applied by aircraft or truck.
b. Ground LV liquid or granular treatments are applied by power sprayers or back pack sprayers.
c. Various formulations of biorational mosquito larvicide products are applied by hand.
3. Treatment of marshlands - Marshlands are treated when found to be conducive to mosquito breeding in sufficient quantities so as to affect human life in and adjacent to those areas.
a. Aerial ULV or LV liquid or granular larvicides are applied by helicopter or fixed wing aircraft.
b. Ground ULV or LV liquid or granular treatments are applied by airboats or other marsh equipment.
B. Adulticide - This control strategy is used as the last resort, after using as much as practical permanent control and biorational larvicides.
1. Treatment thresholds are triggered based on the analysis of adult mosquito surveillance data (See I. B. Adult Mosquito Surveillance).
Insecticide selection and time of application should be based on the distribution and behavior of the target mosquito species. Minimum factors to be considered when deciding the scope of adulticiding effort include:
a. The general ecology of the area (key habitat types, presence of natural barriers)
b. The flight range of vector and nuisance mosquitoes of importance in the area
c. The activity period of the target species, which depends on such factors as:
i. the season of the year, which affects the "window of treatment" (period of greatest mosquito activity and abundance)
ii. the time of the day or night is crucial because most adulticides treat mosquitoes while they are in flight and vulnerable to the application, and the target species may be diurnal (active in the day time) or crepuscular (active after dusk)
iii. in the case of disease vectors, the length of time between the transmission risk and the diapause phase
d. Once arbovirus activity is detected, the following factors should be considered:
i. the human population at risk
ii. the mosquito population density and age
iii. evidence of persistent transmission activity
iv. evaluation of effectiveness of
control of targeted disease mosquito vector
2. Efficacy of adulticides is extremely important. Many factors can adversely affect efficacy. These are:
a. droplet size, must be maintained within the optimum range to avoid efficacy problems.
i. Nozzle selection and correct operational engine pressure will be critical to assure the correct droplet size in hand foggers and ground ULV units. Selection of aerosol generators (nozzles, rotary atomizers, etc.), location and placement of the aerosol generators on the aircraft fuselage, operating pressure and airspeed are all critical in generating the proper droplet sizes in aerial applications.
ii. Droplet measurements should be taken on each spray unit several times during the year to assure droplet size is within optimum size for the product used.
b. Flow rate must be as prescribed in the label to achieve maximum efficacy and avoid overdosing,
c. Concentration of adulticide must be as prescribed in label. Under-dosing reduces efficacy and may lead to development of resistance.
d. Weather conditions, for example, too high wind speeds or no winds blowing, or temperature inversions will hinder adequate droplet dispersion.
e. Equipment maintenance is necessary to provide properly operating equipment essential for maintaining droplet size.
3. Adulticide products of choice are all applied at ultra low volumes (ULV) (except thermal foggers, which are used as handheld units and in some underground applications) by either ground equipment or aircraft. The Environmental Protection Agency (EPA) has determined that insecticides registered nationally for this type of application pose minimum risks to human health and the environment when used according to the pesticide label. A list of recommended adulticides is available in The Insect Pest Management Guide published by the Louisiana Cooperative Extension Service of the LSU AgCenter (see complete reference under Further References and Websites ).
4. Equipment falls in these three categories, depending on the type of terrain:
a. Truck-mounted ULV sprayers, used in areas where there is good accessibility by roads
b. Aircraft ULV applications, used in areas where there is little accessibility for truck usage or in situations where ground ULV treatments would not be sufficient to reduce the adult mosquito populations successfully. Aircraft applications allow for coverage of larger areas in shorter periods, but it is the most costly of the equipment types
c. Portable hand held units, used in localized situations such as barns, around the outside of the homes or in backyards.
C. Operational Factors
1. All personnel (seasonal, part-time) do not need to be certified if they are working under the direct supervision of a certified individual (section D. below). However, these personnel, especially the truck drivers, need to be trained. LMCA strongly recommends the use of "Spray Truck Drivers' Training Program" and has produced an accompanying tape titled "Spraying Safely" (see Websites ). 2. A night supervisor or designated full-time employee shall observe and assist the seasonal part-time employees. Seasonal, part-time personnel normally perform adulticiding at night, including dusk or dawn, and should be trained by full-time personnel.
3. An operational plan must be filed with the state health officer of the DHH/OPH Vector Control Program (see Louisiana Sanitary Code and State Enabling Act section 7725 on approval of ordinances by state health officer).
4. Inspector(s) shall routinely perform larviciding throughout the mosquito season with special emphasis when disease activity occurs (see VII. Disease Surveillance).
D. Louisiana Pesticide Law/Advisory Commission on Pesticides - Rules and Regulations
1. Certification Requirements. Under the authority of the Louisiana Pesticide Law, R.S. 3:3201, et seq., and in accordance with the provisions in R.S. 49:950, et seq., the commissioner of agriculture adopts pesticide regulations. Under these Rules and Regulations (see Pesticide Law), specifically Subchapter R, Section 125., Part B. Subpart h., the Louisiana Department of Agriculture and Forestry (LDAF) requires commercial applicators and state, federal and other government employees using or supervising the use of pesticides in public health programs for the management and control of pests having medical and public health importance to be certified in Category 8. There are two subcategories in Category 8 applicable to mosquito control:
a. Subcategory 8a Mosquito Control: Applicator. This subcategory is for commercial applicators and government employees who are applicators in mosquito control programs.
b. Subcategory 8d Mosquito Control: Program Supervisor. This subcategory is for commercial applicators and government employees who are program supervisors in organized mosquito control programs.An individual applying for certification in Category 8d must have either:
i. a bachelor's degree with at least 12 hours in entomology; or
ii. at least four years of experience in mosquito control working under supervision of a person certified in Category 8d. Required experience must be substantiated by a notarized statement acceptable to the commissioner.
2. Pesticide Record Keeping Requirements. Any person applying pesticides as a commercial applicator including those described above in Category 8, shall accurately maintain, for a period of two years, records of pesticide applications on a record keeping form or record keeping format approved by LDAF. Records described herein must be maintained, within three days of the application, at the physical address of the employer or the physical address on the owner/operator license. A copy of these records shall be provided to any employee of LDAF upon request at a reasonable time during normal working hours. The following information shall be included on that form:
a. owner/operator name, address and license number;
b. certified applicator name, address and certification number;
c. customer name and address;
d. product/brand name;
e. EPA registration number;
f. restricted/general use pesticide;
g. application date;
h. crop/type of application;
i. location of application;
j. size of area treated (acres, square feet, or minutes of spraying);
k. rate of application;
l. total amount of product (concentrate) applied;
m. applicator;
n. certification number of applicator (if applicable).
3. Handling Pesticide Spills/Emergencies by Commercial Applicators. All uncontained spills of more than one gallon liquid or four pounds dry weight must be reported to the director of Pesticides and Environmental Programs at LDAF within 24 hours by telephone and by written notice within three days. The spill hotline telephone number is (225) 925-3763, available 24 hours a day. |