Pesticides have helped improve food production and fight off insect-borne diseases, but they also have a well-documented dark side. Various pesticides have been linked to birth defects, cancer and other health problems in humans, as well as declines in wildlife ranging from bees to bald eagles.
The modern success of organic and biodynamic farming has helped remind us what we can do without synthetic pesticides, but insects still cause major problems worldwide — especially mosquitoes. And now a boom in lighting technology is beginning to hint at unexpected alternatives to chemical pesticides: lasers and light-emitting diodes, or LEDs.
The basic idea of using light to fight insects isn't new. Bug zappers, for instance, have long taken advantage of flying insects' attraction to light. Yellow and green fluorescent lights are also commonly used to reduce insect activity. A reflective mulching sheet has even been found to repel aphids and whiteflies when placed between rows of crops.
But the rapid growth of lighting technology is now raising hopes for more ambitious strategies, some of which might eventually help reduce the need for synthetic pesticides.
Bug zappers lure insects inside a cage and then electrocute them, a primitive form of pest-control lighting. (Photo: David Keyzer [CC by 2.0]/Flickr)
Scientists have known for more than a century that ultraviolet (UV) light can kill microbes, making it useful for purifying water, food and even air. But thanks to the advancement of LEDs and lasers in the past two decades, we can now make light do things that would have seemed impossible a century ago.
Unlike the wires and gases of incandescent and fluorescent bulbs, solid-state lighting offers intricate control over wavelength, color and tone. The boom in LED technology has been largely motivated by energy efficiency, but the environmental perks of LEDs are increasingly rivaled by other benefits like light therapy or pest control. That's due to technological growth as well as recent biological research on light, says Fred Maxik, co-founder and chief technology officer of Florida-based Lighting Science Group. (Full disclosure: Lighting Science Group is associated with Pegasus Capital Advisors, an MNN sponsor.)
"It took a convergence of scientific discovery about what light can do and the technological efficiency to be able to actually do it," Maxik says. "We can get a great deal of really interesting, fine controls now, where we can manipulate the wavelengths of light. And light is really the only energy by which life on this planet has been created and exists. So the fact that it can have all these other influences and powers in biology that we're just discovering is something that's really fascinating."
The photonic fence uses lasers to detect and disable female mosquitoes. (Photo: Intellectual Ventures)
There are several ways light can be used to wage war on insects. One of the most radical methods, known as a "photonic fence," uses lasers to identify and shoot down mosquitoes in midair. The concept was unveiled several years ago by Washington-based Intellectual Ventures, which began developing it for the Bill & Melinda Gates Foundation in 2007 as a way to fight malaria. Critics have argued it's impractical, since malaria tends to plague rural parts of developing countries that have spotty or nonexistent electrical grids, making a network of laser fences seem implausible.
But thanks to improvements in laser technology as well as solar energy, the photonic fence is now powered by solar panels. Earlier this month, Intellectual Ventures' Global Good program announced a research agreement with Lighting Science Group to develop not just the photonic fence, but also other "field-ready prototypes that offer an environmentally responsible alternative to chemical pesticides."
The photonic fence uses an LED array to cast infrared light on a retroreflective surface several yards away, which sends the light back to a camera lens attached to the LED array. The lens can thus detect any insect that tries to cross this "fence" of infrared light — and that's where things get interesting.
When the photonic fence is breached, it immediately hits the intruder with a harmless diagnostic laser. This laser measures the insect's wingbeat frequency to identify the species; it's even sensitive enough to tell the difference between male and female mosquitoes, only the latter of which drink blood. Non-target insects are allowed to pass, but if the intruder turns out to be a female mosquito, a second laser hits her with just enough energy to burn off her wings. All this happens in a fraction of a second, before the mosquito has time to cross the fence and enter the protected area.
See the video below for a demonstration of how the photonic fence works:
While the photonic fence is low-power enough to run off-grid, it may still not be quite ready for prime time. It remains too expensive to be a widespread weapon against malaria, but the cost is falling, and Maxik says it will fall faster once the fence finally hits the market.
"The commercial enterprise in the developed world will greatly support its use at low cost in the developing world," Maxik says. "When you go into areas like here in Florida, people pay a lot of money to keep mosquitoes out of their yards, and those commercial opportunities can help us drive down the cost for using them in less developed areas."
"It's in sort of an emerging stage," he adds. "It has gone beyond pure research. It's sort of in between development and commercialization. We're not dealing with the bare science anymore; we're dealing with prototypes. I think we could see the first field trials of lab units in the next 12 months." The fence would likely be used as a supplement to other mosquito-control methods, like bed nets or newer strategies such as genetically modified mosquitoes that can't produce viable offspring.
Broad 'spectrum' pesticides
The photonic fence was designed to fend off mosquitoes, but Maxik says it could be recalibrated to target the wingbeat frequency of almost any flying insect. In addition to defending homes, schools and hospitals from bloodsuckers, for example, virtual fences might one day be used to protect farm fields from crop-killing flies and beetles. That could potentially help organic farms increase their output and help conventional farms curtail their use of insecticides, some of which have been linked to health problems in humans as well as colony collapse disorder in bees and other ecological issues.
Lasers are one of a few emerging tactics to fight insects with light. Szabolcs Márka, a physicist at Columbia University, is developing a "light shield" that he says can repel mosquitoes by throwing off their navigation and heat detection. "People concentrate more on studying mosquitoes' olfactory or chemical sensors, but light or heat seemed like an interesting area," Márka said in 2010. "Overloading, damaging or confusing this sensory system can prevent mosquitoes from reaching their prey."
More recently, a December 2014 study revealed that short-wavelength, visible blue light can kill eggs, larvae, pupae and adults of Drosophila melanogaster, a common species of fruit fly. Blue light also proved lethal to mosquitoes and flour beetles, the researchers found, but different wavelengths were required to kill different species. "Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic," the study's authors write. "For some animals, such as insects, blue light is more harmful than UV light."
Beyond protecting crops from pests, LEDs can also provide photosynthetically active light to boost plant growth and control nutrient development, Maxik points out. They could be programmed to attract insects to certain areas, or they could possibly even be set to amplify the natural pressure from predators.
"There may be lights that increase the possibility of predators being around," Maxik says. "There are certain lights that I believe would likely be conducive, or less obtrusive, to things like bats in the area that would create a predator-rich environment."
And despite all our fancy chemicals and lights, hungry predators are still the ultimate pesticide.
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