According to a new study by the U.S. Geological Survey (USGS) Bifenthrin, a pyrethroid insecticide, is widely used in agriculture and as an urban pesticide. Pyrethroids are manmade versions of pyrethrins, which come from chrysanthemum flowers; and though that sounds very safe bifenthrin is harmful to aquatic ecosystems at levels that were previously considered safe. Bifenthrin is already a Restricted Use Pesticide (RUP) which means it can be sold only to “certified applicators.”
Bifenthrin is used to combat common household pests like ants and termites, to control mosquitos that could spread diseases like West Nile and Zika and on crops to kill aphids and other agricultural pests. About 1.2 million pounds of bifenthrin were used in the United States in 2014. Globally in order to improve crop yields as arable land declines the use of pesticides and fertilizers is increasing. In addition, the urban use of pesticides is increasing, in part to mitigate the spread of insect carried disease like Zika and West Nile.
Use of pyrethroids like bifenthrin has increased dramatically over the past 20 years in the United States and elsewhere; driven by the need to replace organophosphate insecticides. Pyrethroids have always been considered less toxic, but it is becoming increasingly clear that these pesticides are now agents of global ecological change. Ecological impact is beyond the breeding of resistance that results from spraying pests with pesticides that are significantly less than 100% effective .
Bifenthrin is insoluble in water and can persist in stream sediments. A USGS survey across the continental United States detected bifenthrin in 58% of the streams sampled. The USGS found concentrations of bifenthrin as high as 23.9 μg bifenthrin/g organic carbon (OC) in stream sediment. In global surveys, regional freshwater biodiversity was decreased in areas where pesticides were used, and pesticides, especially pyrethroids, were detected above regulatory thresholds at a greater frequency than expected.
In this study the USGS scientists evaluated the effects of bifenthrin on natural communities of stream invertebrates, such as mayflies and midges, using artificial streams. Exposure to bifenthrin concentrations previously thought benign caused the insect populations to become less abundant and diverse, and caused an increase in algal growth as the larvae that feed on algae decreased. The insecticide also altered the timing of insect emergence from the larval state to become adults and complete their life cycle.
According to Travis Schmidt, a USGS ecologist and the lead scientist on the study “The results of this experiment demonstrate that not only do aquatic insects die at concentrations of bifenthrin previously thought nontoxic, but that bifenthrin changes the way that stream ecosystems function. Bifenthrin disrupts the ability of insects to control algal blooms, and disrupts the emergence of flying aquatic insects that are a food source for bats, birds and other animals in and around rivers.”
There are over 600 products containing bifenthrin available in the United States.When you have pesticides applied to your home be aware of what the company is using. Product names of bifentrhin include Talstar, Bifenthrine, Brigade, Capture, FMC 54800, OMS3024, Torant (with Clofentezine), and Zipak (with Amitraz), but ask for the product information sheet for any pesticide used in or around your home.
Schmidt, T.S., Rogers, H.A., Hladik, M.L., Dabney, B.L., Mahler, B.J., Van Metre, P.C., 2016, Bifenthrin causes trophic cascade and altered insect emergences in mesocosms: implications for small streams: U.S. Geological Survey data release, http://dx.doi.org/10.5066/F7SX6BBZ.