Icause of insects billions of dollars in crop damage every year, prompting farmers to apply pesticides on an industrial scale, at enormous expense and often with unwelcome ecological side effects. They take this carpet bombing approach because they lack information on where and when it is best to target pests and no one wants to use too little pesticide and thus risk losing crops. Technologists at FarmSense, a Riverside, California, company hope to change that.
The established approach to detecting insect pests, especially moths, is to use sticky traps with pheromone baits. Pheromones are chemicals that animals use to communicate and especially to attract members of the opposite sex. A properly primed sticky trap gives a clear idea of the number and type of pests around, but not with enough detail for the precise application of pest control measures. Such traps, however, have changed little in the past few decades, except that some are now equipped with a digital camera that broadcasts a daily picture of the trapped insects. FarmSense researchers believe they can do better.
The company’s device, FlightSensor, has been undergoing full-scale testing on farms since 2020 and is about to be made available to everyone. It does not catch insects. Rather, it scans them with a laser as they fly. The intuition of the developers was that the shadows of the passing wings produce the same oscillating signal as the sound of the flapping of the wings recorded by a microphone. This approach is similar to bouncing a laser beam off a glass window to detect the vibrations of a conversation in the room beyond, a technique used in espionage for decades.
FlightSensor’s technology is based on the work of Eamonn Keogh, one of the founders of FarmSense, who is also a professor at the Riverside campus of the University of California. Dr. Keogh helped pioneer the field of “computational entomology,” in which special algorithms receive data from scanners and learn to determine the sex and species of passing creatures. FarmSense claims to have more digital insect data than the rest of the world combined.
For the first tranche of targets, the results are impressive. Navel moths, in particular, are a common pest of almond and pistachio trees, both of which are important to California agriculture. FlightSensor can accurately identify them more than 99% of the time. And the algorithm is still improving its capabilities and adding new species as it gets more data. Sometimes it can distinguish insects that, to a human eye, look identical.
FarmSense’s optical approach works better than microphones for recording wing flaps because the investigated insects are quiet and the sound they emit is easily lost in background noise. Bees and house flies buzz loudly. But the moths and the trichogrammatid wasps that parasitize them (or, better, their caterpillars), and are therefore of almost equal interest to farmers, are almost imperceptible. However, they are easily detectable by the laser. And while sticky traps are at least one alternative for large moths, the FarmSense sensor detects everything, down to trichograms one-thousandth the size of the moths these wasps are interested in.
In contrast to existing traps, which only report the total numbers captured over a given period, the new sensors record each insect as it arrives, revealing patterns of day and night activity. In one case, FarmSense was able to show a farmer that navel moths only appeared in his fields between three and five in the morning. So instead of spraying disruptive pheromones during the hours of darkness, it is able to limit the regurgitation of these chemicals to the times the moths are active, reducing the amount of pheromone required by 80%. American farmers spend hundreds of millions of dollars a year to reduce pest pheromones, so reducing their use in this way should lead to useful savings.
There should also be ecological benefits. In particular, pesticides of all kinds often have side effects on benign and even desirable insects. Using a more focused approach that implemented fewer of them would reduce the problem.
An additional advantage of the new sensors is their lack of maintenance. The sticky traps eventually stop being sticky, due to accumulation of dust or dead bugs, so someone has to replace the sticky papers. FlightSensor will work for months, reducing labor and other associated costs.
The sensors should also prove useful for academic entomologists. Marta Skowron Volponi of the University of Gdansk, Poland, is using them to observe clearwing moths that mimic bees. They might help her discover how insects manage to look like bees as well as look like them. Meanwhile, on the campus of the University of California at Davis, Joanna Chiu is using them to study the daily business of Drosophila, a fruit fly that is one of the workhorses of genetics. From farm to laboratory, then, listening to insects with light could soon become all the rage. ■
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