Earlier this year Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura won the Nobel Prize in Physics for their development of an efficient blue light-emitting diode (blue LED).

It was a well-deserved victory for the Japanese scientists whose invention continues to impact our lives in ways we often don’t even notice. It could be in the display you’re looking at right now or it could be helping some of the millions of people in parts of the world without electrical infrastructure get affordable lights for their homes.

And now in a report published in Scientific Reports, a team of researchers from Tohoku University have found a new use for blue LED. When used in the right frequency it can be an effective, safe, clean, and cheap way to kill insects. For the first time, they showed that visible light around the blue part of the spectrum is lethal to insects such as mosquitoes and fruit flies.

■ Red light at night, insects’ delight

In the experiment, the team of Masatoshi Hori, Kazuki Shibuya, Mitsunari Sato, and Yoshino Sato gathered samples of three species of insects; fruit flies (Drosophila melanogaster), London Underground mosquito (Culex pipiens f. molestus), and confused flour beetles (Tribolium confusum). The names of these bugs are probably worthy of their own article, but we can’t get sidetracked now.

The team then hit these insects with different intensities of colored lights at different stages of their development from egg to adult. Interestingly, they found that wavelengths of light from ultraviolet (378 nanometers) to visible blue-green (508nm) killed off the bugs, whereas wavelengths of light in red and yellow had essentially no effect.

■ Different lights for different bugs

Even more interestingly, the wavelength of light did not directly correspond to its lethalness. For example, fruit flies dropped dead with under a 467nm far more efficiently than with any other longer or shorter wavelengths. Mosquitoes on the other hand were weaker to a more lavender 417nm wavelength light. When swapped, only a few fruit flies went down under 417nm, whereas mosquitoes barely flinched at the 467nm light.

▼ Graphs showing the percentage of fruit flies (figure1) and mosquitoes (figure2) killed by different wavelengths of light. Notice that simple blue light was far more effective than UV light against fruit flies.

It’s as if every species of insect had their own unique “key” wavelength that unlocked their demise. In addition each insect’s weakness to visible light seemed to correspond to their own lifestyles. Mosquitos tend to fly freely in the sunlight, and as such they are also resilient against most wavelengths except for a relatively high dose of purple light.

Confused flour beetles however, tend to live in dark environments and also happen to be weak against a wider range of wavelengths (404nm to 467nm). It appears that the behavior of these creatures is not to avoid light altogether, but rather to avoid certain concentrations of certain wavelengths of light contained in sunlight.

■ How does it work?

This all leaves us with the question of why this works. That’s a little outside of the scope of this experiment, but the Tohoku U team presumes it’s similar to the damaging effects UV light can have on cells.

In the case of blue/violet lights on insects, certain wavelengths appear to stimulate the production of a type of molecule called reactive oxygen species (ROS). These molecules begin to wreak havoc on a cellular level leading up to significant tissue damage in the insect and ultimately death.

While the exact mechanics aren’t completely known, it has been determined that regular light in just the right measures and doses can be an incredibly effective insecticide. This means we may some day be able to control crop destroying and disease carrying pests cheaply, easily, and without the use of dangerous poisons.

This also shows us that even simple things like blue lights have powers we may not fully comprehend yet. Now if you’ll excuse me, I have to dig those old PC glasses out of the closet.

Source: Scientific Reports (English), Tohoku University 1, 2 (Japanese)
Top Image: Wikipedia – AfroBrazillian (modified by RocketNews24)