Non Low-Impact Pesticides: Pyrethroids
Pyrethroids are broad-spectrum insecticides, effective against a wide range of flying, crawling, chewing, and sucking insects of the orders Coleoptera, Diptera, Hemiptera (Homoptera and Heteroptera), Hymenoptera, Lepidoptera, Orthoptera, and Thysanoptera.
They are synthetic chemicals similar to the natural insecticide pyrethrum which comes from the chrysanthemum plant, but they remain effective for longer periods of time. Pyrethroids have been synthesized to be similar to pyrethrins yet more stable in the environment. In New Jersey, use of pyrethroids is considered non-low impact. All notification and posting requirements must be followed when these pesticides are to be used.
ASTDR reported that concentrated formulations of pyrethroids were classified as restricted use pesticides by the EPA in 1995 (EPA 2000). In the case of permethrin, for example, all formulations for all uses as broadcast sprays on agricultural crops are restricted because of potential adverse effects on aquatic organisms; products labeled for spot treatment (livestock and premise treatments) are not classified as restricted use.
With the exception of deltamethrin, pyrethroids are a complex mixture of isomers rather than one single pure compound. The production of pyrethroids with differing isomeric ratios is one reason for the wide variation in reported toxicities of these compounds.
See below for a brief list of some pyrethroid active ingredients:
Extoxnet and ASTDR provide that pyrethroids tend to be more effective than natural pyrethrins. Most pyrethroids have a longer residual half life in the environment than pyrethrum. Pyrethroid compounds are eventually degraded by the microorganisms in soil and water. They can also be degraded by sunlight at the surfaces of water, soil, or plants. However, some of the more recently developed pyrethroids can persist in the environment for a few months before they are degraded. Hence, pyrethroids are harder on beneficials in an outdoor setting.
- ASTDR Tox Facts
- EPA. 2000. Restricted use products (RUP) report: October 2000. U.S. Environmental Protection Agency. Office of Pesticide Programs. April 2, 2001.
- NPIC Fact Sheet: Permethrin
- NPIC Fact Sheet: Pyrethrins Versus Pyrethroids.
- NPIC Fact Sheet: Lambda-Cyhalothrin – General
- NPIC Fact Sheet: Cypermethrin
- New Jersey WPS Fact Sheet on Health Hazards
- Synthetic Pyrethroids For Mosquito Control