Study and evaluation of the efficiency of mosquito traps using CO2 and attractive pheromones.

Catherine Lavallée-Chouinard is a graduate of the Professional Degree Program in Bioecology (Quebec), and Camille Muranyi-Kovacs is a last year student of the Masters Program in Littoral and Coastal Management. Both of them are working on a study to measure the impact of mosquito control at the Research Institute for the Conservation of Mediterranean Wetlands Tour du Valat in France, created by Dr Luc Hoffmann in 1964.

Camille and Catherine during the Test du Mollet at Le Sambuc. Photo credit: B. Soler

The mosquito control project has been conducted over the last few years with the spread of the Bti bacteria (Bacilus thuringiensis israelensis) on the Camargue’ wetlands. The Bti is a bacteria used as a biological control agent for the larvae stages of certain kind of flies and mosquitoes. Bti produces toxins that are effective in killing various species of nematocera, including mosquitoes and other insects like chironomidae, while having almost no direct effect on other organisms. Indirectly, it affects lots of different species, since mosquito larvae are the basis of the ecosystem’s food chain.

There are five different types of mosquitoes in the Camargue: Ochlerotatus caspius, Culex pipiens, Anopheles hyrcanus, Aedes vexans and, during the winter, Ochlerotatus detritus. They are very common in the area and it is difficult to differentiate them. In some areas around the world, they can transmit several diseases, especially to animals.

Combination of CO2 and pheromones ©B. Soler

Now there is a new method in place for mosquito control, using mosquito traps and Tour du Valat is in charge of the evaluation of the project. The evaluation program held in the Camargue, in the Natural Reserve of la Tour du Valat and the village Le Sambuc, aims to evaluate the efficiency of the traps designed to catch mosquitoes in urban areas. The project is using sixteen traps designed to attract female mosquitoes with a combination of CO2 and octenol pheromones. This emulates human breathing and sweating. When the mosquitoes are near the traps, the ventilation system draws them into the net. The project measures the impact of this new system on other insects and animals and compares the results with the Bti mosquito control.

Catherine changing the net ©B. Soler

To develop this test, Camille and Catherine capture individuals by emptying the nets of the traps in the morning and in the evening, between 9 and 10 pm. Each trap is composed of a wooden box which has a small door with a net inside to catch the insects.

Every day, the team take the nets with the mosquitoes and separates them from other captured species, as they need to weight the mosquitoes and calculate the total number of individuals caught in each trap. Once a week, the team identifies all the different insects captured by three of the sixteen traps to be able to measure the impact of the traps on the individuals of each population (including different species of mosquitoes).

In addition, in the evenings, Camille and Catherine do the so called Test du Mollet, which consists in waiting near three of the sixteen traps and near two uncontrolled zones for mosquitoes to try to bite them so they can suck them with a tube. With this test, they evaluate how many mosquitoes want to bite them in 10 minutes, so that they can measure the efficiency of the traps.

Crystal tube used in the Test du Mollet. ©B. Soler.

Since the surveys started, the results have shown that there are 80% more mosquitoes that try to bite people in the area without traps than in areas where the traps are installed. During a test, they capture no more than five mosquitoes in the urban nucleus and almost one hundred individuals in the natural area.

It should be noted that they also evaluate the influence of the project on the swallow colony living in Le Sambuc, as they are insectivorous and eat flies and mosquitoes. Twice a week they monitor the evolution of the nests to identify the impact in the feeding of the swallows’ chicks.

Camille monitoring a nest. © C. Muranyi-Kovacs

As Camille affirms: “This brand new method to control mosquitoes helps to maintain the food chain and the ecosystem’s natural balance, as the traps don’t kill the larvae which feed a huge number of different animal species”.

For Catherine, this project was important to the better understanding of the effects of the mosquito control on the human population. “People want them gone because they can transmit diseases, but we can’t just kill them and ignore the fact that they have an important place in the whole life cycle. We need to make a compromise to control their negative effects in a wise manner. This project is a great modern idea to find an ecological way to minimise the mosquito population without eliminating it altogether, so as to keep the equilibrium of the wheel of life.”

As Catherine says: “As a fauna technician of the mosquito control project, I learned a lot about insect identification and about their life habits. There are so many and we are always learning about them”.

Following the IUCN and MedWet campaign #NatureForAll and #WetlandsForAll, the young researchers agree that a wetland is for them an entire ecosystem that is really important for a lot of animals and also for humans: where there is a wetland, there is life.

More information

Since the project started, the team has published facts sheets and advises on a Facebook page, completely dedicated to mosquitoes. Did you know, for example, that mosquitoes pollinate the cacao flowers?

If you want to know more interesting data, visit their Facebook page here (in French).

Ecosystem programm at la Tour du Valat

Contact

Brigitte Poulin, Ecosystem programm’s director at La Tour du Valat mail

Camille Muranyi-Kovacs mail

Catherine Lavallée-Chouinard mail