Nav: Home

Biting backfire: Some mosquitoes actually benefit from pesticide application

June 17, 2019

The common perception that pesticides reduce or eliminate target insect species may not always hold. Jennifer Weathered and Edd Hammill report that the impacts of agricultural pesticides on assemblages of aquatic insects varied resulting in distinct ecological winners and losers within aquatic communities. While pesticides reduced many species, the evolution of pesticide resistance allowed the mosquito Wyeomyia abebala to actually benefit from the application of the pesticide-Dimenthoate. This benefit appeared to occur as pesticide-resistant mosquitoes were able to colonize habitats that had reduced numbers of predators and competitors due to the direct effects of Dimenthoate. Their results are reported in a recent issue of Oecologia (

Weathered and Hammill, a student and faculty member from the College of Natural Resources at Utah State University, conducted extensive analyses of aquatic invertebrate communities within tropical bromeliads. They found that invertebrate biodiversity was reduced in bromeliads exposed to the pesticides compared to assemblages from pristine, non-agricultural areas. Surprisingly however, bromeliads from areas with pesticide use exhibited high densities of W. abebala. "Our toxicity bioassays showed that W. abebala from agricultural areas had ten times the Dimethoate tolerance compared to non-agricultural W. abebala. Combining the toxicity experiments with field observations gave us a better understanding of possible mechanisms driving community patterns across landscapes," says Jenn Weathered. Additional analyses indicated that the loss of a predatory damselfly, Mecistogaser modesta, from pesticide-treated locations allowed pesticide-resistant mosquitoes to colonize these habitats that lacked predators. The results were confirmed in both a laboratory and a field transplant experiment where mosquito density was impacted by pesticide use and the presence of the damselfly, but not by the original location of the bromeliads. "Our results show that the addition of novel chemicals into natural systems may lead to the opposite result of what we'd expect, and that we must think about effects on whole communities of species," says Edd Hammill.

Results of this study indicate that biodiversity of aquatic invertebrates was strongly reduced in habitats exposed to an agricultural pesticide, but that differential resistance responses by some invertebrates allowed some non-intuitive increases in species that have the potential to impact human health. The authors stress that to understand the response of novel stressors on individual species, assessment of entire communities of organisms needs to be considered.

S.J. & Jessie E. Quinney College of Natural Resources, Utah State University

Related Biodiversity Articles:

Biodiversity is 3-D
The species-area relationship (SAC) is a long-time considered pattern in ecology and is discussed in most of academic Ecology books.
Thought Antarctica's biodiversity was doing well? Think again
Antarctica and the Southern Ocean are not in better environmental shape than the rest of the world.
Antarctica's biodiversity is under threat
A unique international study has debunked the popular view that Antarctica and the Southern Ocean are in much better ecological shape than the rest of the world.
Poor outlook for biodiversity in Antarctica
The popular view that Antarctica and the Southern Ocean are in a much better environmental shape than the rest of the world has been brought into question in a study publishing on March 28 in the open access journal PLOS Biology, by an international team lead by Steven L.
Temperature drives biodiversity
Why is the diversity of animals and plants so unevenly distributed on our planet?
Biodiversity needs citizen scientists
Could birdwatching or monitoring tree blossoms in your community make a difference in global environmental research?
Biodiversity loss in forests will be pricey
A new global assessment of forests -- perhaps the largest terrestrial repositories of biodiversity -- suggests that, on average, a 10 percent loss in biodiversity leads to a 2 to 3 percent loss in the productivity, including biomass, that forests can offer.
Biodiversity falls below 'safe levels' globally
Levels of global biodiversity loss may negatively impact on ecosystem function and the sustainability of human societies, according to UCL-led research.
Unravelling the costs of rubber agriculture on biodiversity
A striking decline in ant biodiversity found on land converted to a rubber plantation in China.
Nitrogen is a neglected threat to biodiversity
Nitrogen pollution is a recognized threat to sensitive species and ecosystems.

Related Biodiversity Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".