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Situation update
Last updated: August 31, 2024
Both the aerial spray in parts of Plymouth County and the truck-based spraying in southern Worcester County began Tuesday evening, August 27, 2024. It is important to note that spraying is weather dependent, and plans could change up to the last minute. Maps of both spray areas are posted at the following website: Mosquito Spray Map (massnrc.org). These maps are being updated daily to reflect the areas that were sprayed the night before. The areas involved are listed below:
- COMPLETED: Aerial spraying will take place in Plymouth County in the following locations: All of the town of Carver, and parts of the following towns: Halifax, Kingston, Middleborough, Plymouth, Plympton, Rochester, and Wareham
- COMPLETED: Truck-based spraying will take place in the following five towns in southern Worcester County: Douglas, Dudley, Oxford, Sutton, and Uxbridge
Because of the need to maintain flexibility to adapt to emergent weather conditions, if you are within one of the spray zones, you should assume that your area is being sprayed each night until you check the spray map and confirm that your area has been sprayed. Spraying begins at dusk and will end by dawn each day. Should you see planes in the air or trucks in your area prior to dusk, they are either getting in position or scouting out the area prior to starting the spray.
What is Eastern equine encephalitis (EEE)?
Eastern equine encephalitis (EEE) is a rare but serious disease caused by a virus that can affect people of all ages. EEE is generally spread to humans through the bite of a mosquito infected with the virus. EEE can cause severe illness and possibly lead to death in any age group; however, people under age 15 and over age 50 are at particular risk. EEE does not occur every year, but based on current evidence, a high risk of occurrence of human cases exists in 2024.
What does it mean to find the presence of positive mosquito samples?
Because EEE does not occur every year, the identification of EEE virus in mosquitoes indicates that activity is present during the current season. There are two types of mosquitoes that can be found with EEE: bird-biting species and mammal-biting species. When virus is found in mammal-biting mosquitoes, the risk for human disease increases because these mosquitoes are much more likely to bite people. Based on the positive findings of EEE in mosquitoes this year, the occurrence of animal and human cases, and the forecast environmental conditions, a high risk of occurrence of human cases exists in parts of southeastern Massachusetts and southern Worcester County.
What can be done to reduce risk of EEE?
Understanding the risk and being vigilant about practicing personal protective behaviors are the best ways to decrease the risk of EEE. These protective actions include:
- using repellents with an EPA-registered active ingredient according to the instructions on the label any time you are outdoors;
- while outdoors, wearing clothing that covers your skin;
- rescheduling outdoor activity to avoid the hours between dusk and dawn;
- checking screens and repairing holes or replacing those that do not fit tightly; and
- reducing areas of standing water, where mosquitoes breed, is also important (e.g., removing garbage cans, flowerpots, bird baths, discarded tires, or other containers that hold water). This is most useful for decreasing West Nile virus risk but is also good practice against EEE.
In communities that belong to a Mosquito Control District (MCD), the local Board of Health works with the MCD to make decisions about control activities that may include reducing populations of mosquitoes while they are still in their immature or larval state and reducing populations of adult, flying mosquitoes using truck-based ground spraying.
When is aerial spraying of insecticides considered?
In situations where there is a high risk of human disease, the state’s response plan recommends consideration of the use of an aerial pesticide spray in the evening and overnight hours to reduce the number of infected, adult mosquitoes in the specific areas of high risk. Truck-mounted ground spraying is already taking place in some communities in Massachusetts.
It should be noted that although the aerial spraying is considered necessary to reduce human risk, it will not eliminate risk. It is critical that residents protect themselves from mosquito bites by staying indoors during peak mosquito hours, applying insect repellent when outdoors, draining standing water where mosquitoes breed, and repairing screens.
Why is truck-mounted ground spraying being used in Worcester County while aerial spraying is being used in Plymouth County?
In Plymouth County, the Mosquito Control District has been conducting truck-based ground spraying in response to EEE infected mosquitoes during the season. Risk, however, continues to be elevated. Because of this ongoing risk, an aerial spray will be used to supplement the work that has already been performed in high-risk regions of Plymouth County. In southern Worcester County, only two of the towns at high or critical risk are members of the Mosquito Control District. Those towns have received truck-based spraying to help reduce risk, but the five remaining towns have not. In this area, truck-mounted ground spraying will be used in those five towns that have not already had mosquito spraying to reduce risk.
How are aerial spraying and truck-mounted ground spraying conducted?
Spraying begins in the early evening and continues until approximately 4:30 am the next morning. Mosquito control professionals apply a pesticide approved for this use as an ultra-low volume (ULV) spray. ULV sprayers dispense very fine aerosol droplets that stay aloft and kill adult mosquitoes on contact.
How long will the aerial and truck-mounted ground spraying take?
Effective spraying is heavily weather dependent, and changes to the planned schedule can occur last minute. This means that expected timelines and completion dates are subject to change. Information will be shared as it becomes available.
What pesticide product would be used in the spraying?
The pesticide used during aerial applications is called Anvil 10+10, an EPA-registered product extensively tested and used in both ground-level and aerial spraying in the U.S. to control mosquitoes. Anvil 10+10 contains two active ingredients: Sumithrin and Piperonyl butoxide (PBO). Sumithrin is a pyrethroid insecticide that kills insects when the insect comes into direct contact with it. Sumithrin is also found in pesticide products used indoors, pet shampoos, and tick control treatments. Piperonyl butoxide serves to increase the ability of Sumithrin to kill mosquitoes. Sumithrin and PBO decompose with exposure to light and air and are rapidly inactivated with a half-life of less than one day in the air and on plants. These compounds have proven to be highly effective in killing mosquitoes worldwide for over 20 years.
Are these pesticides used elsewhere to control mosquitoes?
Yes. Other states (e.g., New York, New Jersey, Illinois, Delaware, North Carolina, Arkansas, Florida, Alabama, Louisiana, Texas) regularly apply these same products.
Can these targeted ground and aerial sprays with adulticides harm insects or wildlife?
The US Environmental Protection Agency (EPA) has evaluated these pesticides for their safety and has determined that they do not pose an unreasonable risk to birds or mammals, if used according to the product label directions.
Anvil and other similar pesticides are toxic to land-dwelling and water-dwelling invertebrates (e.g., dragonflies, beetles) and to fish. There is less risk to fish in larger ponds than in smaller ones and the risks to large natural water bodies are minimal. Those with small ornamental fishponds in their yards, however, may want to cover them during the night of spraying. These fishponds can be uncovered in the morning after spraying has been completed.
Is there a risk to drinking water sources?
No. Aerial spraying is not expected to have any impacts on surface water or drinking water. Surface drinking water sources are mapped and aerial spraying will not occur over these water supply reservoirs. Also, the product is rapidly inactivated and decomposes in sunlight and air, does not dissolve easily in water, and is broken down by microorganisms in streams and water bodies that receive sunlight. Therefore, residues in water would not be expected. Because of these characteristics and the fact that spraying does not occur over drinking water supply reservoirs, exposure through drinking water is not expected.
Are there any health impacts associated with exposure to Anvil 10+10?
Anvil 10+10 is applied using an ultra-low volume (ULV) aerosol that uses very small quantities of the insecticide. It is unlikely a person would be exposed to amounts that would cause adverse health effects. Although special precautions are unnecessary for most people, residents in the affected areas who prefer to avoid or minimize exposure can stay indoors during spraying. People with known sensitivities to chemicals or existing respiratory conditions, such as asthma, are encouraged to stay indoors during spraying to reduce the chances of aggravating those conditions. Consumption of vegetables and fruits grown in the treated area or drinking water that might be taken from surface water bodies near spraying operations is considered safe.
Are there precautions I should take if spraying occurs in my area?
Spraying is conducted at night and the active ingredients of the pesticide product used for aerial application for mosquito control generally break down quickly and leave no residue. Although not necessary for most people, there are extra steps that can be followed in areas where spraying is scheduled to take place. People with known sensitivities to chemicals or with existing respiratory conditions, such as asthma, are encouraged to stay indoors during spraying to reduce the chances of aggravating those conditions. Other steps that may be considered include:
- Those in the spray areas can close windows and turn off fans that pull air from the outside. Shut off air conditioners or use a setting for recirculating indoor air. In very hot weather, you can open the windows or turn fans and air conditioners back on soon after the aerial spraying is completed.
- Bring pets indoors during spraying. Although pets that remain outdoors could be exposed to small amounts of Anvil 10+10, they are not expected to experience adverse health effects from the spraying. There are many pesticide products (e.g., flea collars, pet shampoo, dips) containing similar ingredients that are used directly on pets to control ticks and insects.
- If clothes or outdoor items are exposed during spraying, wash them with soap and water.
- No special precaution or waiting periods are needed for outdoor swimming pools.
As noted above, people may want to cover small ornamental fishponds in their yard during the night of spraying. These fishponds can be uncovered in the morning after spraying has been completed.
Are there any restrictions on consuming fruits and vegetables from home gardens or local farms?
No. The U.S. EPA has established a tolerance (acceptable level) for the product that allows wide-area mosquito application on food crops, fodder crops, pasture, and grazing areas. The application is not expected to leave a detectable residue on food crops, pastures, or forage crops. Livestock may graze in treated areas following the application. As always, consumers should rinse any homegrown or purchased fruits and vegetables with water before preparation or consumption.
Do livestock need to be brought indoors during spraying?
No. Livestock can remain outside during the spray and may continue to graze in treated areas.
Should beekeepers take special precautions to protect the bees before or after aerial spraying?
Negative impacts on honeybee colonies are not expected as the aerial spraying will take place at night. If bees are congregating outside the hive box(es), beekeepers may consider applying a cover to the hive entrance or over the entire hive box(es) using a loose wet cloth (burlap, sheet, etc.) to prevent bees from exiting, avoiding direct contact during the application. Remove covers and additional boxes placed on hives as soon as possible the morning following application.
If miticides have been applied and there is concern about ventilation during covering suggested above, beekeepers may consider adding an additional empty box on top to increase ventilation within the hive during the application. Remove covers and additional boxes placed on hives as soon as possible the morning following application.
The product being applied has a very short half-life (one day) and breaks down rapidly in sunlight. The Department has conducted monitoring of honeybee hives during similar past aerial application and has received no reports of any negative effects on honeybees from the use of this product.
For further questions regarding bees, contact MDAR Crop and Pest Services at (617) 626-1700.
What should I do if I think that I am experiencing an adverse reaction to pesticide spraying?
If you believe you may be experiencing any health effects from pesticides, call your health care provider or the Massachusetts Poison Control Center at 800-222-1222. If you need immediate medical attention, call 911 for assistance.
Who do I contact to learn more about spraying in my area?
For information about the status of the 2024 response to EEE, check this website here daily. Updates will also be shared via local media outlets.
For information about what has been sprayed and what is left to do, please see 2024 Massachusetts Aerial Spray Map. This map will be updated as information becomes available.
For questions about aerial spraying, contact MDAR Crop and Pest Services at mosquitoprogram@mass.gov.
For the most updated information about EEE risk and how to prevent disease, call the DPH Division of Epidemiology at (617) 983-6800 or visit the DPH website at Mosquito-borne Diseases | Mass.gov for updated mosquito results, maps, and incidence of positive mosquito samples.
For questions about exposure to the pesticide, call the DPH Bureau of Climate and Environmental Health at (617) 624-5757 or by email at DPHToxicology@mass.gov.
For general information about mosquito control, contact the State Reclamation and Mosquito Control Board within MDAR at (508) 281-6786.
| Date published: | August 29, 2024 |
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