Larval surveys are conducted to locate the exact areas in which mosquitoes are breeding, estimate their relative abundance and to treat or eliminate larval habitats. Reducing populations of immature mosquitoes (larvae and pupae) reduces the reliance and expense of adulticides. Many larvicidal products are biorational and come in sustained released formulations. Larvicides are available in a variety of formulations such as briquettes, granules and oils and should be selected based on the type of treatment site as well as the duration of control needed.
- Larval inspections of urban sites. Inspect any containers holding water including rain barrels, tires, buckets, coolers, watering cans, flower pots, bird baths, pet dishes, trash, gutters and tree holes.
- Evaluate the data collected. Information should include if larvae and pupae collected, the type and size of container and mosquito species. Locations should be recorded to construct a map of positive larval sites for re-inspection when appropriate.
- Review data. Review the data to ensure that the most current and least ecologically impactful control strategy is used and that the efficacy has been evaluated. Larvicides are available in a variety of formulations and should be selected based on the site of treatment, the developmental stage targeted, and the duration of control needed.
- Review mapping of the sites once it has been completed.
NOMTCB has a history of research and operational use of biological control agents including Gambusia (mosquito fish), copepods (small crustaceans) and Toxorhynchites (cannibal mosquitoes). In February, we began to increase the production of these at our Biological Control Laboratory in New Orleans East. Sustained control efforts will likely involve the experimental releases of biological control species in areas at higher risk such as those with frequent illegal waste tire dumping, prolonged tire storage or high number of containers positive for immature mosquitoes.
- Biological control
- Mosquito fish program. Gambusia affinis is a commonly used fish species which consume larvae, reproduce readily and are successful, long-term solution for mosquito control in permanent water habitats. The Louisiana Department of Wildlife & Fisheries permits release into man-made structures like fountains and pools but are prohibited from being released into natural water bodies.
- Copepods. Copepods are small (0.5 -1.5 mm) crustaceans found naturally in marine and fresh water habitats. Mesocyclops longisetus and Macrocyclops albidus are aggressive species which can consume first and second instar mosquito larvae (>40 larvae/day). Successful control of Ae. albopictus and Ae. aegypti larvae has been achieved through the addition of copepods in containers such as tire, barrels and cisterns. Copepods have a varied diet allowing them to survive once mosquito larvae have been depleted and can tolerate dry periods. Door-to-door source reduction campaigns (habitat reduction & education), Involve community & neighborhood groups for sustained effect, community-wide events (such as waste tire collection)
- Copepod Poster
- CDC Fact Sheets http://www.cdc.gov/zika/fs-posters/index.html
- EPA approved and registered larvicides used as needed. Larvicides have a variety of formulations and each type used will be based on the situation and need.
- Ultra-low volume (ULV) larvicide application,
- Truck - Grizzly ULV/ LV application unit with SmartFlow tracking
- Aerial application – possible but can only be applied by helicopter over congested air space, NOMTCB does not have the capacity at this time
- Granular or liquid larvicides
- Back-pack application - Maruyama sprayer, granules Spheratax SPH® good for large, difficult to reach areas such as abandoned home with containers and tire piles
- Can also be applied by hand directly to breeding sites
Adulticide applications are effective in causing a rapid reduction in the vector mosquito population but typically must be reapplied to have a sustained effect.
- Device: SOLO or Stihl SR200 Backpack Spray Mister
- Insecticide: Talstar® (bifenthrin)
- Aerial application
- Device: Britten-Norman Islander Aircraft
- Insecticide: Dibrom® (naled)
- Truck/ Ground ULV
- Device: Ford F-150s with ULV units: Guardian 190ES with Monitor 4 tracking system, or Grizzly with SmartFlow tracking
- Insecticide: Fyfanon ULV® (malathion)
- Pesticide rotation - use of different adulticides for additional modes of control including residual and knockdown
- Scourge® (resmithrin), DeltaGard® (deltamethrin)
- Permanone® (permithrin) - persistent
Evaluating aerial ultra-low volume (ULV) adulticiding
Monitoring Insecticide Susceptibility and Resistance
Repeated applications of insecticide can result in chemical tolerance, and there are several methods that can be utilized to test mosquito populations for resistance. It is important that testing is done continuously and if resistance is detected, changes should be made in response such as increased application rate or a change in the class or type of insecticide used.
- Bottle Bioassays – laboratory assay, conducted prior to and following the spray season determines baseline susceptibility and if there has been a change in insecticide resistance
- Cage tests – field test, using a cage of field-collected mosquitoes, and ground or aerial ULV equipment to determine spray efficacy
Bottle bioassays conducted by NOMTCB with local populations of Ae. albopictus and Ae. aegypti have determined susceptibility to insecticides currently in operational use in the district at application rates. Over the last two years, NOMTCB has evaluated the efficacy of the aerial and ground ULV (truck) against populations of Aedes mosquitoes. The results of these studies demonstrated 80-90% mortality in caged mosquitoes placed in open and sequestered locations in neighborhoods in Mid-City and the 7th Ward.
Surveillance and Container Assessments for the Prevention of Mosquito-borne Disease
The Louisiana Department of Agriculture and Forestry (LDAF) requires records be kept on pesticide applications including the site of application, specific chemical information and rate applied. LDAF provides "Pesticide Applicator Record Keeping forms" for use by certified applicators. Applications must be made in adherence to Louisiana Pesticide La (L.R.S. 3:3201-3310), state pesticide regulations (LAC7:XXIII) and the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and also under the rules set forth in the Louisiana Pollutant Discharge Elimination System General Permit (LAG870000) These records must be kept on file and available for inspection at the NOMTCB Administration building. Only certified applicators will apply pesticides.