How Structured Pest Control Leverages Pyrethroid Perimeter Sprays.

Chemical based insecticide use has been widely discouraged, due to the associated toxicity problems. The good news is that this has resulted in vastly decreased usage amongst consumers and business owners. But, what many people don’t know is that there are natural insectides available. A species of chrysanthemum, Chrysanthemum cinerariaefolium, produces insect fighting chemicals, called pyrethrins, naturally. The dried, powdered form of the flowers were first used as an insecticide in the U.S. in 1860. Today, pyrethrins are extracted from the flowers using solvents, allowing for the manufacture of insecticides used in both organic farming and structural pest control. Pyrethroids, which are synthetic versions on the natural pyrethrins from chrysanthemums are also commonly used insecticides.

Use of Perimeter Sprays


Pesticides are sprayed extensively throughout the US - Image courtesy of Dollar Photo Club

Over the past couple of decades, there has been significant changes in the pest control methods adopted by both professionals and consumers. When over use of organophosphate pesticides such as diazinon and chlorpyrifos were shown to lead to high levels of toxic contamination of California bays, creeks and rivers, resulting in threats to aquatic life, organophosphate’s were banned in 1996.

However, perimeter spraying has continued, and a major consequence of the organophosphate ban was an increase in the amount of pyrethroids applied, (as well as the introduction of new pesticides including: indoxacarb, fipronil, neonicotinoids, imidacloprid, dinotefuran, and thiamethoyrethrum.)

The insecticidal activity of pyrethrins can be quickly deactivated by sunlight. This means that there are few water contamination concerns because the pesticides are usually destroyed within 3-12 days after they are applied (Moore 1973). However, to make pyrethrins more resistant to sunlight, synthetic pyrethroids were developed, which quickly proved disastrous for the environment. These human-made pesticides have half-lives of over a month and are more potent than pyrethrins. Naturally this also means they are more dangerous, as they are far more toxic to mammals. Natural pyrethrins are comprised of carbon, oxygen, and hydrogen, but pyrethroids also feature chlorine, fluorine, and cyanide components (Farinas 2012). For example, bifenthrin, a pyrethroid which contains fluorine and chlorine with a half-life in aquatic sediments of 8-16 months, is 21x more toxic to the aquatic indicator organism Hyalella azteca, than natural pyrethrins.


Pyrethroid Toxicity in California Water


Pyrethroid toxicity has been identified in creeks, rivers, and wetlands in California. Much of the contamination is due to storm water runoff from areas ranging from farmlands to business centers and residential areas. In one study, conducted during periods of winter storms, more than 50% of sediment samples in a 13 km (7.8 mi) stretch of the American river were found to be toxic to the aquatic organism “Hyalella azteca.” The same study found the pyrethroid bifenthrin present in 11 of 12 runoff sources into the same said river (Weston and Lydy 2012; Moran 2010).


Addressing Pyrethroid Contamination Nationwide


Pyrethroids are not only contaminating streams in California but have been found in stream sediments nationwide. A study found pyrethroids in 78% of stream bed samples from 36 streams in 25 states. Bifenthrin was the most frequently detected pyrethroid (Hladik and Kuivila 2012).


Reducing Use of Perimeter Sprays


A survey by Meta Research indicated that approximately 83% of the pyrethroids used in California structural pest control are applied outside with 50% used as perimeter applications of pesticides to control ants, spiders, and occasional invaders. This includes walls and foundations, horizontally on soil or turf and on surfaces such as patios and driveways (Meta Research 2010). Pyrethroids are currently the most commonly used broadspectrum, nonfumigant insecticides in California structural pest control (CA DPR 2010).


Though water contamination with pyrethroids continues to be a problem, there are signs of some positive changes. Problems with pesticide contamination of water led to creation of the EcoWise Certified® Program in California in 2006 (Quarles 2006). An EcoWise Certified Service must adhere to EcoWise Standards which encourages the reduction of pesticide exposure and contamination of water. Professionals can be trained and certified through an online certification programs. Furthermore, the introduction of a usage ban during wet weather, (limiting applications to horizontal surfaces such as soil surface, mulch, gravel, lawn, turf and groundcover for spot treatments) as well applications to horizontal surfaces with standing water, sewers, storm drains, gutters and drainage systems should all help reduce water contamination levels.


Working together by reducing home use, using only pest control agencies who select green techniques and natural pyrethroids can help preserve water quality as well as the health of humans and animals.