How Pesticides Can Actually Increase Mosquito Numbers

— Written By
en Español / em Português
Español

El inglés es el idioma de control de esta página. En la medida en que haya algún conflicto entre la traducción al inglés y la traducción, el inglés prevalece.

Al hacer clic en el enlace de traducción se activa un servicio de traducción gratuito para convertir la página al español. Al igual que con cualquier traducción por Internet, la conversión no es sensible al contexto y puede que no traduzca el texto en su significado original. NC State Extension no garantiza la exactitud del texto traducido. Por favor, tenga en cuenta que algunas aplicaciones y/o servicios pueden no funcionar como se espera cuando se traducen.


Português

Inglês é o idioma de controle desta página. Na medida que haja algum conflito entre o texto original em Inglês e a tradução, o Inglês prevalece.

Ao clicar no link de tradução, um serviço gratuito de tradução será ativado para converter a página para o Português. Como em qualquer tradução pela internet, a conversão não é sensivel ao contexto e pode não ocorrer a tradução para o significado orginal. O serviço de Extensão da Carolina do Norte (NC State Extension) não garante a exatidão do texto traduzido. Por favor, observe que algumas funções ou serviços podem não funcionar como esperado após a tradução.


English

English is the controlling language of this page. To the extent there is any conflict between the English text and the translation, English controls.

Clicking on the translation link activates a free translation service to convert the page to Spanish. As with any Internet translation, the conversion is not context-sensitive and may not translate the text to its original meaning. NC State Extension does not guarantee the accuracy of the translated text. Please note that some applications and/or services may not function as expected when translated.

Collapse ▲

Jake Buhler | 6/2/2019 | National Geographic

Insecticides in at least one area are not only failing to control mosquitoes, new research suggests, they’re actually allowing the bloodsucking pests to thrive—by killing off their predators.

The study, published this month in the journalOecologia, reveals a new wrinkle in how insecticides may be impacting ecosystems. Mosquitoes in the study area in Costa Rica have evolved resistance to common chemicals meant to kill them and other pests. The mosquitoes’ predators, meanwhile, have not kept pace with that evolution—and that has allowed the mosquito population to boom.

Edd Hammill, an ecologist at Utah State University and lead author of the study, first got an inkling that insecticides might not be having their intended effect while conducting research in orange plantations in northern Costa Rica.

Asian mosquito biting a person's finger

“We felt like we were getting a lot more mosquito bites in plantations than in pristine areas and started to wonder why,” Hammill says.

So he and his team surveyed where the mosquitoes were coming from: bromeliads, a group of plants found in warm parts of the Americas, often growing on tree branches. The water-filled spaces between their tightly overlapping leaves host a whole community of insect larvae, including mosquitoes of the species Wyeomyia abebela.

The team looked at bromeliads in plantations—some of which had been treated with insecticides for more than twenty years—and in untreated forests. The Costa Rican growers use dimethoate to treat their orange trees for plant lice, but it kills many other insect species too. In the U.S. it’s widely used on citrus, corn, and other crops.

Hammill’s team found that despite all the insecticide, the orange plantations were hosting twice as many mosquitoes as the pristine forests. But damselfly larvae—a major predator of larval mosquitoes—were conspicuously missing from the plantations.

When the researchers took the insects into the lab and exposed them to varying levels of dimethoate, they found that the plantation mosquitoes tolerated concentrations ten times higher than the forest mosquitoes. But the plantation damselflies had evolved no such resistance.

The resistant mosquitoes thus appear to have found a sweet spot: a nursery habitat for their young that is devoid of predatory damselflies. There, they flourish.

Read the entire article