Facts about Aerial Adulticiding and Larviciding

Originally posted Sept. 1, 2016

See the CDC comments on Aerial adulticiding and larviciding further down this page.

There is a great deal of information on the internet about aerial adulticiding and larviciding. There are claims aerial spraying will not work against Aedes aegypti or Aedes albopictus.  There are claims against the use of naled.  Some of the information is misinformation.

Some claim aerial adulticiding and larviciding does not work against Aedes aegypti.

Some control experts/researchers claim aerial spraying for controlling the Zika virus is not effective because the Aedes aegypti and albopictus mosquitoes that can transmit Zika are living inside homes and are protected from aerial spray. Their perspective is based on less developed countries that typically deal with mosquito borne diseases. Those areas have mainly been in locations where there are no screens on houses, no air-conditioning and no municipal water system.

In Lee County, Florida, the majority of homes have screens and many have air-conditioning. The Aedes aegypti and albopictus mosquitoes are found around homes and businesses and only found inside structures when given access. These Aedes aegypti and albopictus do not live in the structures; they are living in close proximity to a home or structure. Lee County Mosquito Control District inspectors rarely find Aedes aegypti or albopictus in homes where mosquitoes are allowed inside by torn screens, doors left open, pets going in and out bringing mosquitoes in with them or something that allows mosquitoes to fly inside the home. Aedes aegypti and albopictus are very rarely found breeding inside a home or structure within Lee County. With municipal water systems, residents no longer store water in containers inside their homes; therefore, Aedes aegypti and albopictus do not have breeding areas within the structure.

When the Florida Keys had a local outbreak of Dengue, which is transmitted by the Aedes aegypti mosquito, they started with the basics and moved to every modern mosquito control technology available including aerial larvicide and adulticide treatments to stop further transmission. Florida mosquito control programs have learned from the work and reporting of the Florida Keys Mosquito Control District on how to control Aedes aegypti. Lee County Mosquito Control District will utilize aerial adulticiding and larviciding treatments that have been shown to control Aedes aegypti in Florida, if needed.

Some claim naled is banned in Europe, not true.

Naled was not banned for mosquito control in Europe. Since aerial application of adulticides for mosquito control in Europe is utilized very rarely, AMVAC simply chose not to support the product under the EU Reregistration program. The statement from the official EU document reads as follows: For the active substance naled, the notifier informed the Commission on 2 December 2004 that it no longer wished to seek the inclusion of that substance in Annex I to Directive 91/414/EEC. Consequently, that active substance should not be included in that Annex and Member States should withdraw all authorizations for plant protection products containing naled. Further the EU review stated: Naled does not show any evidence of delayed neurotoxic potential following either single or repeated administration.

Some claim naled causes neurological effects in people. Not true when used as directed by label.

Available data supports that naled applied according to the label does not cause neurotoxic effects in humans. Studies that are required by regulatory authorities look at this potential effect and those have been submitted to and reviewed by the EU and EPA. The EU concluded: Naled does not show any evidence of delayed neurotoxic potential following either single or repeated administration. The EPA in its most recent regulatory decision has concluded that when used as labeled, the agency is not concerned about adverse effects to humans.

Some basics on risk.

It is the dose and duration of exposure that determine the risk to human and environmental health. Potential effects from any product use are directly related to the amount of exposure a person gets. For example, many everyday items that we all come in contact with daily can be deadly to a person at too high a dose. The dose rate for uses of naled in agriculture is much higher than those used for mosquito control. Naled is packaged in a closed system and applied – from an airplane or helicopter – at the equivalent of one ounce or less per air column acre for mosquito control and usually from an altitude of 300 feet.  Lee County Mosquito Control District uses 0.50 to 0.66 ounces per acre from 350 feet. The packaging, application method, timing of the application and corresponding droplet size -less than one third the width of a human hair in size- ensures that there is essentially no exposure from the application to people.

There is a tremendous difference in the mechanics and products used for treating the immature, mosquito larvae and the adult mosquito. Videos of larvicide treatments can be confused as adulticiding treatment.  Videos showing aircraft treating in Miami make references that areas are being drenched with naled, an adulticide. They are incorrect, when in fact the video is an aircraft larviciding. For controlling the adult mosquitoes, the rate of use for naled in the Miami project is 1.0 ounce per acre. The droplet size from LCMCD aircraft is around 20 microns. How big is a micron? The droplets are so tiny it would take 9,761,000 droplets of 20 microns to fill the volume of one BB shot. In Miami, the altitude of release is approximately 300 feet above ground. Contrast that to LARVICIDING:  In Miami the rate of release for the larvicide is 32 to 64 times higher at one to two quarts per acre. The droplet VMD is larger by many multiples making the application entirely different. The altitude for the larvicide application is 100 ft. above ground level. They are not treating with naled at the higher larvicide rate.

CDC statements on Aerial Treatment for larval and adult mosquitoes:

When people in a large area are getting sick or when large numbers of mosquitoes are found, airplanes can be used to treat very large areas with insecticides safely, quickly, and efficiently. This process is called aerial spraying. Below is more information on aerial spraying.

Integrated Vector Management

Is aerial spraying an effective tool for killing mosquitoes?

Aerial treatment of areas with products that rapidly reduce both young and adult mosquitoes can help to limit the number of mosquitoes that carry the Zika virus. Repeated aerial applications of insecticide has reduced mosquito populations as a part of an integrated vector management program.

Is aerial spraying alone the best way to control mosquitoes?

• Aerial spraying is only one part of the solution for controlling mosquitoes, but it is the one method that can rapidly reduce the number of mosquitoes spreading Zika in a large area.
  • It is the most effective method when large areas must be treated quickly.
• Aerial spraying is used as part of an integrated mosquito control program to quickly reduce the number of mosquitoes responsible for infecting people with viruses like Zika, dengue, or chikungunya.
• An integrated mosquito control program includes
  • Source reduction.  Eliminating mosquito habitats, such as discarded containers and rain gutters.
  • Structural barriers, such as screens and enclosed, air-conditioned spaces, if possible.
  • Larval mosquito control using the appropriate methods for the habitat.
  • Adult mosquito control using insecticides.
  • Community education efforts related to preventing mosquito bites by wearing EPA-registered insect repellents and protective clothing (long-sleeved shirts and long pants).

Aerial Spraying and Insecticides

Is aerial spraying experimental?

• Aerial spraying is not experimental.
• EPA-registered insecticides are used for aerial spraying EPA-registered insecticides have been studied for their effectiveness and safety when used according to label instructions.
• Aerial spraying, using Naled and other insecticides, has been used in many populated areas of the continental United States, including Miami, Tampa, and New Orleans, to help control mosquitoes.
  • In 2014, almost 6 million acres of land in Florida was aerial sprayed with Naled by mosquito control programs.

Where has Naled been used?

• Naled has been extensively used since the 1950s and is currently applied by aerial and ground spraying to an average of approximately 16 million acres of the continental United States annually.
• It is also used for mosquito control following natural disasters, such as hurricanes and floods. (Human Exposure to Mosquito-Control Pesticides ― Mississippi, North Carolina, and Virginia, 2002 and 2003, CDC, 2005)
• In 2004 and 2005, it was used as part of the emergency responses to Hurricanes Charley, Jeanne, Frances, and Katrina.
• Naled is currently used in the United States by many local governments and mosquito control districts, including the Florida Keys Mosquito Control District, the Lee County Mosquito Control District, and Miami-Dade County.
• Historically, Naled has been used in Puerto Rico in attempts to control dengue.

What happens to Naled once it is sprayed?

• Naled starts to degrade (break down) immediately on surfaces, in water, and in sunlight.
• The chemical dichlorvos (DDVP) can be created when Naled degrades. It also breaks down quickly.
• In small quantities DDVP has not been shown to cause health problems in people.
• DDVP does not build up in breast milk or breast tissue.

What is Bti and how does it work?

• Bacillus thuringiensis subspecies israelensis (Bti) is a naturally occurring bacteria found in soils.
• Bti produces toxins that kill the larvae of mosquitoes and blackflies when swallowed. The toxins cause death by starvation and only begin working when swallowed by certain insects (larvae of mosquitoes, blackflies, and fungus gnats).
• There are several strains of Bacillus thuringiensis (Bt) that kill other insect larva like caterpillars and beetles. These are not the same as Bti.

Can Bti only be applied through aerial spraying?

• No, Bti is often applied using methods that are not aerial spraying.
• Bti can be applied using truck-mounted or backpack spraying. It can also be found as dunks or briquettes that can be put in areas of standing water that cannot be emptied, such as fountains and ornamental ponds, septic tanks, and unchlorinated pools.
• Dunks are currently being distributed in Zika prevention kits.

Aerial Spraying and Human Health

Is aerial spraying of insecticides dangerous/harmful to human health?

• No, during aerial spraying, a small amount of insecticide is sprayed over an area, about 1 ounce (two tablespoons) per acre or about the size of a football field.
• This small amount does not pose a health risk to people or pets in the area that is sprayed.
• When aerial spraying is done correctly, it does not cause asthma attacks.
• There is a possibility that spraying of a larvicide, like Bti, can cause eye irritation if a person is outside and looking up when spraying takes place.
• EPA-registered products are used for aerial spraying. The label instructions are followed by a licensed professional.
• If people prefer to stay inside and close windows and doors when spraying takes place they can, but it is not necessary.

Does aerial spraying cause asthma attacks?

• No, when aerial spraying is done correctly, it does not cause asthma attacks.
• When applied according to label instructions, EPA-registered insecticides do not pose a risk to human health or the environment.
• Research shows that ultra-low volume (ULV) application for mosquito control does not increase the risk of asthma for people living in treatment areas (Karpati et al. 2004, Currier et al. 2005, Duprey et al. 2008).

Will Naled cause cancer?

• No, EPA has classified Naled as Group E “Evidence of Non-carcinogenicity for Humans,” meaning that there is no evidence that it causes cancer in people.
• During aerial spraying, a small amount of insecticide is sprayed over an area, about 1 ounce (two tablespoons) per acre or about the size of a football field.
• Droplets float in the air and kill adult mosquitoes on contact.
• Naled starts to degrade (break down) immediately on surfaces, in water, and in sunlight.
• EPA conducted risk assessments for Naled and calculated risks under different exposure scenarios.
• Because of the very small amount of active ingredient released per acre of ground during aerial spraying, EPA found that for all scenarios and exposures were hundreds or thousands of times below an amount that might pose a health concern.
• In an evaluation of thousands of people who conducted agricultural spraying using many types of insecticides, including organophosphates like Naled, no increased risk of any type of cancer was found during the 7-11 years of follow up (Schinasi & Leon, 2008).
• However, at high doses, for example if the person doing the spraying is exposed to Naled directly in amounts that are well above those for normal labeled uses, Naled and other organophosphates can overstimulate the nervous system, causing nausea, dizziness, or confusion. This is why it is very important that those who actually work with Naled strictly follow label instructions.
  • Severe high-dose poisoning with any organophosphate can cause convulsions, respiratory paralysis, and death.
  • It is extremely unlikely that any person would come into contact with this amount of Naled when it is applied by a licensed professional according to label instructions.

Will Bti affect human health?

• Bti has not been found to pose a health risk to people or pets.
• There is a possibility that spraying larvicides, like Bti, can cause eye irritation if a person is outside when spraying takes place.
• Bti is an EPA-registered insecticide. EPA-registered insecticides have been studied for their effectiveness and safety when used according to label instructions.
• Existing residential and area-wide uses, like aerial or truck spraying, have been evaluated and found to be safe. Using Bti to kill mosquito larvae may reduce the risk of getting infected with Zika virus.
• If people prefer to stay inside when spraying takes place they can, but it is not necessary.

Aerial Spraying and Animals

Will aerial spraying hurt pets and other animals?

• No, when aerial spraying is done correctly, it does not harm animals.
• During aerial spraying, a small amount of insecticide is sprayed over an area, about 1 ounce (two tablespoons) per acre, or about the size of a football field.
• This small amount does not pose a health risk to people or pets in the area that is sprayed.
• EPA-registered products are used for aerial spraying. The label instructions are followed by  a licensed professional.If people prefer to bring pets inside when spraying takes place they can, but it is not necessary.
• Aerial spraying will not harm  fish or animals that live in the water. People do not need to cover fish ponds when spraying takes place. If a larvicide is sprayed, it is better if ponds are not covered.

Will aerial spraying kill bees?

• Aerial spraying can be done in ways that minimize risk to bees.
• Spraying Naled can kill bees outside of their hives at the time of spraying; therefore, spraying is limited to dawn or dusk when bees are inside their hives.
• Because Naled breaks down quickly, it does not pose a risk to the honey bee populations.
  • Studies show that honey production between hives in treated and untreated sites did not show significantly different quantities of honey over the course of a season.
  • For additional protection, urban bee keepers inside the spray zone can cover their hives when spraying occurs.
• Although significant exposure to bees would not occur with Naled application at dawn and dusk, beekeepers can reduce potential exposure to bee colonies even more by covering colonies and preventing bees from exiting during designated treatment periods or, if possible, relocating colonies to an untreated site.
• The spraying of mosquito larvicides will not impact bees.

Will aerial spraying kill birds or other animals?

• No, when aerial spraying is done correctly, it does not harm birds or other animals.
• The insecticides used for aerial spraying do not pose risks to wildlife or the environment.
• Aerial spraying does not cause long-term harm to the environment or local ecosystem, even if spraying happens more than once.
• EPA-registered insecticides used for aerial spraying break down rapidly in the environment, and it displays low toxicity to birds and mammals.
• Aerial spraying will not harm coquis or fish or animals that live in the water. People do not need to cover fish ponds when spraying takes place. If a larvicide is sprayed, it is better if ponds are not covered.

Will Bti affect animals or wildlife?

• No, Bti does not pose a risk to other mammals, birds, or aquatic life, including coqui frogs in Puerto Rico. The toxins it produces only begin working once swallowed by certain insects (larvae of mosquitoes, blackflies, and fungus gnats).

Aerial Spraying and the Environment

Will aerial spraying pollute water?

• No, when aerial spraying is done correctly, it does not pollute water.
• Research shows that, when applied according to label instructions, EPA-registered insecticides sprayed in low levels (about two tablespoons per acre [4,046 square meters]) does not cause long-term harm to the environment or local ecosystem, even if spraying happens more than once.

Will chemicals from aerial spraying contaminate soil?

• No, when chemicals used in aerial spraying are used correctly, they will not contaminate soil.
• Aerial spraying does not cause harm to the environment or local ecosystem, even if spraying happens more than once.
• When applied according to label instructions, EPA-registered insecticides do not pose a risk to human health or the environment.

More information can be found on the US Environmental Protection Agency’s website.

Will Bti affect water sources?

• No. Because Bti has no toxic effect on people, it poses no risk of contamination to water supplies.