Triggering a stress response in mosquitoes by exposing them to chemicals emitted by one of their natural enemies makes pesticide much more effective at lower concentrations, researchers in Belgium find. Matthew Stock reports.
Mosquitoes are widely considered the deadliest creatures on earth. They transmit diseases, including malaria - responsible for the deaths of 400,000 people each year in sub-Saharan Africa alone. And they're building resistance to many existing pesticides, and those still effective can be toxic to other wildlife. At this lab in Belgium, they're developing a new method for killing mosquitoes. They're testing a chemical based on the scent produced by the backswimmer -- one of the mosquitoes natural predators. It triggers a stress response in the insect, which in turn makes pesticide more lethal when used together. In effect, they're scarring them to death. (SOUNDBITE) (English) LIN OP DE BEECK, PHD STUDENT AT UNIVERSITY OF LEUVEN, SAYING: "I found that when I used a cocktail of these two products, so the synthetic pheromones and the biological pesticide BTI (Bacillus thuringiensis israelensis), that when combined the mortality of the mosquitoes increased a lot. So when I used both substances separately there would be no mortality, but when combined together you would see a strong increase in mortality of the mosquitoes." Known as a predator cue, the scent of the backswimmer can be synthetically produced. Key to the cocktail's success is the lower dose of pesticide needed to kill the mosquito when mixed with this predator cue. (SOUNDBITE) (English) LIN OP DE BEECK, PHD STUDENT AT UNIVERSITY OF LEUVEN, SAYING: "Even though the BTI is in a low dose they cannot handle the stress from this biological pesticide anymore. So it's the extra stress of fear of being eaten that will make sure that they die more easily from this biological pesticide." The initial research was conducted in the lab. The next step is to study the impact of the chemical cocktail in a more natural setting. The race for an effective and sustainable method for controlling mosquito-borne diseases is more fraught than ever Zika is one such virus, linked with a rare birth defect. It's now spread to almost 60 countries since it was identified last year in Brazil.