Cass County uses a number of synthetic pyrethroids to control adult mosquitoes. Pyrethroids are synthetic chemical insecticides that act in a similar manner to pyrethrins, which are derived from chrysanthemum flowers. Pyrethroids are widely used for controlling various organisms including head lice. Permethrin, bifenthrin, etofenprox, and resmethrin are synthetic pyrethroids commonly used in mosquito control programs to kill adult mosquitoes.
- Permethrin has been registered by EPA since 1977. It is currently registered and sold in a number of products such as household insect foggers; ant and other insect sprays for the home; tick and flea sprays; flea dips & sprays; collars for cats and dogs; termite treatments; agricultural and livestock products; for the treatment of head and body lice; and mosquito abatement products. Cass County utilizes permethrin adulticides in all ULV applications including aerial applications.
Cass County has 24 truck mounted foggers that are calibrated to apply ultra low volume(ULV) spray of pythroid insecticides. Our ULV trucks put out droplets around 20 microns in diameter or 0.0008 inches across (about the width of a living cell). These droplets are in the air for about half an hour and travel up to 300ft. Cass County Vector Control currently uses an application rate of approximately 0.0035 lbs per acre of permethrin, or about 0.4 grams of active ingredient per "average" household yard. Compare that to a single can of common household pesticide used in backyards for control of mosquitoes and flying insects; each contains about 1.7 grams of permethrin and other similar active pesticides - about what a Vector Control truck would put out over an acre of land. In contrast, application rates for certain agricultural products such as apples can be up to 0.4 lbs of permethrin per acre of crop (181 grams per acre).
Another way to think about permethrin mosquito spraying is to look at the dose applied to a single square foot of area. During an aerial application the rate of product is 0.007 lbs/acre. The dose per square foot becomes 0.073 milligrams of product. For comparison; a popular head lice treatment contains 280 mg of permethrin per dose. Assuming an 8 inch diameter skull is a perfect sphere- the dosage of pesticide is 5,000x larger on the treated head than what is present after an aerial application for control of mosquitoes over the same area. If you follow the recommended treatment and require a second dose- the total amount on the skull is 10,000x more than aerial spraying.
A panel of international experts convened by The World Health Organization and The United Nations published a 1989 report concluding that "There are no indications that permethrin, when used as recommended, will have an adverse effect on human beings". The report further describes studies of permethrin toxicity in mammals such as rats, guinea pigs, and dogs where no observed effect was seen when animals were directly feed up to 100 milligram of permethrin per kilogram of body weight per day in long term studies. One study that was acknowledged in the report showed no observable effects of permethrin dosages at a scale of a 30 pound dog receiving 1.5 grams or permethrin daily over three months of trial. In order to ingest that 1.5 gram nontoxic dose of pesticide, one would have to consume all the permethrin sprayed out by a ULV sprayer over an area 3/4 the size of a football field or about 40,000 square feet every day. Studies in rats suggest that a lethal dose of permethrin is almost six times the amount studied or approximately the total of material sprayed over a quarter of million square feet. Bare in mind that an acute overdose that could result in death of over counter pain relievers such as aspirin or acetaminophen is about 150 milligrams per kilogram or a dose of approximately 7.5 grams for an adult human.
Lethal Dosages of Common Drugs and Substances
|*note: 1 acre(43,560 sq ft) treatment of permethrin is 3175 milligrams (0.007 lbs) or less|
Nonetheless it is always advisable to practice good hygiene. Wash your hands prior to eating food, smoking, chewing gum, removing contact lenses, before and after using the restroom, and other times which ingesting environmental contaminates can be possible. If you do come in contact with an application of any pesticide for mosquito control; simply remove yourself from the area and wash with clean water. Clothing can be left out in sunlight where the permethrin will break down from ultra violet light exposure and then washed. Wash dirt and environmental contaminates off garden and store bought fruits and vegetable with clean water to remove residues. Wash you hands and arms after applying flea dips to your pets or bathing them with flea and tick shampoo; remove soiled towels and air dry in sunlight before washing. Read all precautionary statements on lice, flea, and tick treatments. And at home always keep all potentially hazardous materials away from children and pets as 75% of all poisoning is from accidental ingestion.
To learn how to learn the steps to controlling adult mosquitoes around your property click here.
Cass County's current adult mosquito control material inventory:
For more information:
If you are a resident in a city/township, or subdivision, please contact your officials to schedule adult mosquito spraying. These applications occur on a contract basis only.
If you are part of a subdivision or city/township wishing to establish a contract with the county you must contact your representatives to do so.