Acoustic Pest Control

(Image Credit: Joe Raedle/Getty Images)

We live in a time where there is a lot of angst around government monitoring. With phones being tapped and browser histories being combed through. But did you know that eavesdropping has been going on for centuries? Acoustics – an interdisciplinary science, which includes topics such as vibration, sound, ultrasound and infrasound - has seen great people from history such as Pythagoras and Aristotle listening in. Hearing is a crucial means of survival for all species in the animal world - including bugs, which, ironically, are now being bugged. Vibration sensors are monitoring their communication in a bid to hijack their mating calls to develop an acoustic pesticide.

Florida’s Blight

Florida’s citrus industry is faced with an incurable disease - citrus greening - that has caused losses to the tune of billions of dollars. The culprit? The Asian citrus psyllid. But it is not so much the psyllid that is a nuisance; it’s what it brings with it.

When a male psyllid is looking for a mate, he positions himself on a twig and sends vibrations along nearby leaves and branches while keenly listening out for a female’s response. If it comes, he dutifully travels in her direction and some weeks later they spawn numerous offspring, which, as adults will carry the deadly Candidatus Liberibacter asiaticus bacteria. These bacteria turn the leaves of citrus trees a sickly yellow and make the fruit bitter and stunted. There is no cure. The tree simply dies over time. Bioacoustics could be the industry’s solution.

Bioacoustics

Bioacoustics is a science that combines biology and acoustics. It involves the investigation of sound production; auditory anatomy and function; as well as sonar and acoustic tracking in animals - including humans. Richard Mankin, a research entomologist with the US Department of Agriculture, along with other researchers, is developing vibration traps that intercept psyllid mating calls.

“The route I’m trying to take is looking at disrupting mating and putting out signals that either outcompete the females and bring males to a trapping system, or just make it difficult for males and females to communicate with each other,” says Richard.

Richard aims to reduce the overreliance of pesticides on Florida’s citrus farms one because he fears the psyllids will build up a resistance to the treatment, and second because of the environmental implications.

The High Cost Of Pest Control

According to the Guardian, pesticides could cost sub-Saharan Africa USD 90 billion in illness. Indeed, in an audit of pesticide shipments to Kenya, carried out in the early 90’s, the country emerged at the time as among the highest pesticide users in sub-Saharan Africa.

Pesticide use is highly concentrated in large-scale farms – where most crops are grown for the export market. This means that for the average small-scale farmer, government-approved pesticides are too expensive leading them to resort to irregularly imported and more harmful alternatives. But it is not only the use of these pesticides that is of concern, it is also how they are stored and disposed of.

In 2008, a pesticide called carbofuran, which was killing off everything in its path, including wildlife, was banned from the country. It is evident then, that an alternative means of pest control would be ideal.

The Acoustic Disruptor

Not the official name of the device but more a description of how it works; consists of a piezoelectric buzzer and a microphone wired to a microcontroller.

It detects incoming male calls and emits a false female response through its buzzer before any nearby psyllids can answer - a delay of about half a second. When the male bug approaches the false female, he is caught and trapped on an adhesive surface and is later collected.

(Image Credit: Device microphone)

He estimates that each device would be effective over a range of 2 feet around a citrus tree, with a cost of construction of between USD 50 and 100. The average small-scale farmer in Kenya owns or leases between 1 and 5 acres of land. Given the small area that this device covers it would be quite a steep investment for these farmers but the research team is working hard to drive the costs down.

Looking To The future

Granted the device is currently targeted for use in Florida’s citrus industry, there is a lot of ongoing research on how acoustics devices can be utilized in pest control. These devices have successfully been used to trap pests such as mosquitoes and cockroaches.

Agriculture is still a very important part of Kenya’s economy with agricultural exports making up the bulk of her GDP. Having alternative ways to ensure consistent crop yields would benefit not only the country but also those countries, which receive her exports.

Sentiments echoed by Richard who says

“Trying to develop electronic-based pest control is a good idea, because it will help the production of food – and we all need all the help we can get to feed the world’s growing population in the future.”