▌How many towns in Vermont spray pesticides along roads to kill adult mosquitoes?
Only the BLSG district sprays pesticides along roads to kill adult mosquitoes.
Eight towns in Vermont are permitted to apply treatments to control mosquito populations. Brandon, Salisbury, Leicester, Goshen, and Pittsford are in the BLSG Insect Control District, and Cornwall, Weybridge, and Bridport are in the Lemon Fair Insect Control District. These contiguous towns are all in Addison or Rutland counties in the Champlain Valley.
A mist of malathion or permethrin is sprayed from trucks driving along roads in the BLSG District. These chemicals kill flying mosquitoes and other small insects. This approach is not used in the Lemon Fair District or in other towns in Vermont.
▌How safe are the chemical pesticides sprayed along roads to kill adult mosquitoes ?
The chemicals sprayed along roads in the BLSG District include malathion and permethrin. The spray trucks have ultra low-volume spray equipment which produces a mist of very small droplets so only a small amount of pesticide must be used. However, the chemicals are highly toxic to many animals including insects, other invertebrates, fish, birds, and some mammals (permethrin is highly toxic to domestic cats).
Malathion has been implicated as a potential human health risk in the following categories (source):
- Endocrine disruption
- Reproductive effects
- Kidney/liver damage
The World Health Organization has classified malathion as “probably carcinogenic to humans.”
Because of the high toxicity of malathion, many insect control districts use only permethrin or other pyrethroid insecticides. Successful control of adult mosquitoes is commonly done without resorting to the more dangerous malathion.
▌Can mosquitoes be controlled without spraying toxic pesticides?
Many insect control districts across the country completely avoid spraying toxic chemicals that kill adult mosquitoes. Instead, they use only larvicides which prevent mosquito larvae from hatching into adult mosquitoes. This approach is very successful in the neighboring Lemon Fair Insect Control District.
▌Are mosquito larvicides safe for people and the environment?
The safest and most effective larvicides are bacterial treatments which kill mosquito larvae while they feed in the shallow water of breeding areas. These bacterial larvicides have no human health effects and only minor environmental effects other than eliminating millions of mosquitoes. Very few aquatic species other than mosquitoes are affected by these larvicides. This is the only type of treatment used in the Lemon Fair Insect Control District.
In the BLSG District, another type of larvicide is applied to mosquito breeding areas. Methoprene is a powerful growth regulator that can kill many types of aquatic insects and other invertebrates including crustaceans and molluscs.
▌Does methoprene cause environmental damage?
Mosquito larvae are very sensitive to methoprene so a low concentration of methoprene in water will prevent mosquito larvae from emerging as adult mosquitoes. Most other freshwater organisms are not as sensitive to methoprene and can survive low concentrations. To avoid killing animals other than mosquitoes, methoprene must be applied at a precise dose which requires estimating the volume of water being treated. This is notoriously difficult to do and therefore it is also difficult to assure that non-target animals will not be harmed. Many governmental bodies have banned or restricted the use of methoprene for mosquito control.
In the BLSG District, methoprene is used to treat vernal pools–temporary wooded ponds which are critical habitats for an unusual suite of aquatic animals. The special animals which depend on vernal pools include amphibians, fairy shrimp, and fingernail clams. Unlike bacterial larvicides, methoprene remains toxic for many weeks and therefore presents a serious threat to vernal pool animals. As vernal pools dry out in late spring, the water volume decreases potentially causing the concentration of methoprene to increase.
Some mosquito control districts have banned the use of methoprene and some districts prohibit its use in vernal pools. If mosquito larvae are abundant in vernal pools, a better control strategy is to use only the safer bacterial larvicides.
▌Are there more mosquitoes in the BLSG district than elsewhere in Vermont?
Mosquito trapping has been done in many parts of Vermont, but the data don’t tell us much about how the numbers of mosquitoes vary across the state. The extensive floodplain swamps and fields along Otter Creek are considered to be prime breeding ground for mosquitoes. The central part of the Otter Creek valley is so flat that it is more like a plain than a valley. In the 30 miles between Rutland and Middlebury, Otter Creek drops only 165 feet in elevation. If you follow the wandering course of the creek, you might drop only four feet per mile. The broad, flat swamps and fields along the creek are under water during most spring seasons, and those hundreds of acres of standing water can allow a lot of mosquitoes to breed. When water levels in flooded fields are just right for mosquito egg laying for one or more years, and then also good for mosquito hatching in a subsequent year, adult mosquito populations can be very high in the BLSG District.
Other species of mosquitoes breed in forests and wetlands away from the Otter Creek floodplain. There is no indication that those mosquitoes are more abundant in the BLSG District than in other areas of Vermont.
▌Have the control efforts of the BLSG District reduced the number of mosquitoes?
No scientific evidence has been collected in Vermont to determine if the number of mosquitoes has increased or decreased over the years. There have been some famously bad mosquito years in the past, but there is no evidence that natural variation in mosquito populations won’t make next year the worst ever.
Roadside spraying of pesticides can reduce the number of mosquitoes near the road for several hours but has no long term effect. This is because
- The spray mist stops working after a few hours,
- Any mosquitoes resting on vegetation are not killed, and
- Mosquitoes a few hundred feet from the road are not affected and can safely invade the roadside area within hours.
Less than 10% of the area of the BLSG District is treated by roadside spraying, so most of the mosquitoes in the District are unaffected and can continue to bother people and breed new generations of mosquitoes.
If there is a long term decrease in the number of mosquitoes in the BLSG District, it might be due to the yearly aerial application of larvicides over thousands of acres of lowland breeding areas. This is the only BLSG control activity which is likely to have caused a long term reduction in nuisance mosquitoes.
▌Does ULV spraying of adulticides kill insects other than mosquitoes?
Ultra low-volume (ULV) spraying produces tiny droplets of liquid containing pesticides. If a small flying insect comes in contact with one or more of these droplets, the insect can be killed. This allows insects to be killed with a very small amount of pesticide. Any insect much larger than a mosquito would have to come into contact with many droplets to be killed. So, after the cloud of spray has dispersed, large insects can fly through the cloud and survive. However, if a large insect flew across the road soon after the spray truck passed, it could be killed by the denser cloud of pesticide.
This careful study demonstrated that many different species of small insects were killed by the well dispersed ULV cloud of pyrethrin sprayed after sunset. The insects and other arthropods that were killed belonged to more than 25 different families including beetles, bugs, flies, bees, and wasps.
Malathion is even more deadly to insects than pyrethroids and certainly kills many types of small insects when sprayed as a ULV mist. So when roadside spraying is done on warm summer nights in Vermont, many insects other than mosquitoes are killed.
▌Does ULV spraying of adulticides kill pollinators?
Most insect pollinators fly during the day and would not encounter pesticide clouds sprayed after dark. However, some daytime pollinators also fly at night, and many species of insect including beetles, moths, flies, and bees are important nighttime pollinators. Many small pollinators could be killed by nighttime spraying. Large diurnal pollinators like honey bees and butterflies will rarely be killed while in flight but bees could be killed if their hives are close to a sprayed road. BLSG recommends that bee hives not be closer than 300 feet from a sprayed road, suggesting that even nighttime ULV spraying has the potential to harm honey bees.
▌Are adulticides sprayed along uninhabited stretches of road, or only near houses?
The spray routes posted by the BLSG Insect Control District include many of the more densely populated roads in the District. They also include many stretches with no houses for a quarter mile or more. If the sprayer is operating along these roads through uninhabited forest or farm land, this pesticide application will not have much effect on the number of mosquitoes which come into contact with people. Adding these toxic chemicals to the environment has no benefit for local residents and could contribute to the development of pesticide resistance in mosquito populations.
The protocols for roadside ULV spraying are most effective when an entire grid of closely spaced roads in a village or suburb is sprayed. This can eliminate a proportion of the adult mosquitoes over an area large enough that mosquitoes from outside the spray zone cannot quickly reinvade. This strategy is viable in only a tiny portion of the BLSG District where there are closely spaced roads. Evening spraying along most spray routes in the BLSG District might have a negligible effect on mosquito numbers by the time people leave their houses the next morning.
▌Can you request that no pesticides be sprayed along roads adjacent to your property?
Yes, landowners can mail a letter requesting that no spraying occur along their property. The letter must be submitted each year by early April and must include a map of the property. Property maps are available for free from Moosalamoo Woods & Waters.
BLSG has offered contradictory information in the past which suggested that they accept these opt-out request by email as well as snail mail and that if you previously submitted a tax map you don’t need to include it again.
▌If you opt out of roadside pesticide spraying, will your property be protected from pesticides?
If a landowner opts out of adulticide spraying, the property boundaries along the road are marked and spraying stops when the BLSG truck reaches the boundary. However, according to the BLSG website, the ultra-low volume droplets kill mosquitoes up to 150 feet from the road and could harm honey bees up to 300 feet from the road. It is clear that substantial concentrations of pesticide can drift onto properties even if the truck does not spray continuously along the road frontage.
Recent requests for no-spray buffer zones (e.g., that spraying stops 150 before a property is reached and starts again 150 feet past the property) have not been honored by the BLSG Insect Control District. Many insect control districts across the country honor 200 or 300 foot buffer zones for residents concerned about toxic effects of pesticides. Without such buffer zones, residents in the BLSG District can opt out of spraying along their road frontage, but cannot opt out of exposure to the pesticide. Many residents see this BLSG policy as an infringement on their private property rights.
▌Does the BLSG spray adulticides on private roads or only on town and state roads?
There are many private roads in the five towns of the BLSG Insect Control District and many of them are included in the regular routes for spraying malathion and permethrin.
The BLSG spray trucks have also sprayed the entire length of private driveways without the landowner’s permission. This is an unacceptable intrusion onto private property. It means that even if your house is far from a spray route you are not necessarily protected from exposure to pesticides. To avoid having a BLSG pesticide truck spray right up to your house, the only option is to opt out of roadside spraying.
▌Does the BLSG spray adulticides in parts of the District other than along designated and published spray routes?
In addition to spraying designated routes, BLSG will visit private homes to spray pesticides to control adult mosquitoes. These homes do not have to be along designated spray routes. If your neighbor requests such treatment, your property could be exposed to pesticides without warning. This applies to everyone in the District, not just to those living along spray routes. BLSG has no mechanism in place to allow property owners to protect themselves from this type of exposure to pesticides.
Although BLSG is required to alert the public before every pesticide application happens, BLSG does not alert anyone when private properties are sprayed by request.
▌Is the BLSG required to alert residents before they spray adulticides?
The BLSG Insect Control District publishes a notice in the spring before larvicide or adulticide application begins. The notice published in several local papers and at the BLSG website alerts landowners that they can opt out of pesticide application along their property.
For the first time, the BLSG starting posting advance notices of roadside spraying at their website in May 2018.
Many residents would like to be alerted whenever spraying happens on their road. This would allow them to take the actions recommended by the EPA if they are concerned about exposure to pesticides (e.g., for malathion: closing windows, bringing in children’s toys, covering gardens). It should be possible for the BLSG District to alert a few people who can announce (e.g., via email or social media) that an action threshold has been reached and spraying will occur that evening.
If your neighbor requests that their property be sprayed (e.g., in advance of an outdoor event), BLSG does not alert anyone of this spraying.
▌Should Vermonters be concerned about mosquito-borne Zika virus?
There is no reason for concern about exposure to mosquito-borne Zika in Vermont. In the US, Zika can be transmitted by mosquito bites, but according to the CDC, there is “no known Zika” from mosquitoes outside of Florida and Texas.
Zika is thought to be transmitted by only two species of mosquitoes (Aedes aegypti and A. albopictus) which are rare or absent in New England. In 2016 , 2017, and 2018 the Vermont Agency of Agriculture and Food Markets monitored for A. albopictus and failed to find any. Populations of A. aegypti have apparently never been present in Vermont.
The BLSG website and numerous BLSG public statements continue to suggest that Vermonters should be concerned about contracting the Zika virus from mosquito bites in Vermont. These statements seem to many as being intended to deceive the public into supporting BLSG’s activities, and are grossly misleading and unwarranted.
▌Should Vermonters be concerned about mosquito-borne West Nile virus?
Since it was first confirmed in the US in 1999, West Nile virus has infected more than 46,000 people in the US and more than 2,000 people have died. Mosquitoes infected with West Nile virus have been found throughout Vermont in past years, so this threat should not be ignored. However, between 1999 and 2016, only 12 cases of West Nile virus were reported in Vermont. No one has died from West Nile virus contracted in Vermont.
New England has a comparatively low per capita incidence of West Nile virus disease. Between 1999 and 2016, the chance each year of developing a serious disease from West Nile virus was zero in most Vermont counties including Rutland County, and less than 1 in 200,000 in Addison County.
This post has more information and links to sources.
▌Should Vermonters be concerned about mosquito-borne Eastern equine encephalitis?
Unlike West Nile virus which has killed more than 2000 people in the United States, Eastern equine encephalitis (EEE) is a rare illness in humans, and only a few cases are reported in the United States each year. Also unlike West Nile virus, EEE is more common in the East and Northeast than in most parts of the United States. Most persons infected with the Eastern equine encephalitis virus have no apparent illness, but severe cases are dangerous and two people in Vermont died from the virus in 2012.
From 2007 to 2016, the average annual incidence of EEE in Rutland County was less than one case per 200,000 people. In all other counties, including Addison County, the 10-year average was zero. This is an exceedingly small risk of contracting the disease. Vermont tests thousands of mosquitoes every year for infection with EEE, and in 2016, 2017 , and 2018 EEE was not found in any mosquitoes and no cases of the disease were reported in people.