Scientists have resurrected an old device to sniff out the exact scents that attract or repel insects, which could then be developed by companies for growers to purchase and use to trap or ward off such crop-damaging pests. 

A Cornell research team is investigating whether the methods could help tackle crop pests such as beetles in vegetables, fruit tree pests including woolly apple aphids, black stem borers and codling moths, and human pests such as mosquitoes.

Credit: Jason Koski/Cornell University

The device, called an electroantennogram, was invented nearly 70 years ago and used for pioneering pheromone research at Cornell in the 1970s. It allows researchers to identify the exact scent molecules detected by an insect’s antennae. These could include pest-attracting molecules (attractants) found in sex pheromones or fruit odors and in pest deterrents that originate in alarm pheromones and warn of dangers.

“With all the pests and invasive species, the application to agriculture is fundamental to be able to track down pests and monitor their population dynamics,” said Christophe Duplais, associate professor of chemical ecology at Cornell AgriTech and leader of a team developing the electroantennogram for agricultural uses. 

In the 1970s, Cornell chemist Wendell Roelofs used an electroantennogram prototype to pioneer insect pheromone research, which led to more than 150 pheromone and attractant discoveries and earned him the 1983 Medal of Science from President Ronald Reagan.

Entomologists and industry experts have identified many pheromones that attract males, but identifying molecules that attract females remains challenging. In many insects, females produce long-range sex pheromones that attract males, which is why most monitoring tools target males. However, females rely on other cues, such as plant odors, to find food on which they lay eggs. When eggs hatch, the larvae eat crops and cause damage. Creating a lure to trap females can provide insights into their presence, predict crop damage, and notify growers on when to spray. 

“In all the pest management we’re doing across different crops, we monitor many kinds of insects, but for moth pests, it’s the male, it’s never the female,” Duplais said.

In their current research, Duplais and tree fruit entomologist Monique Rivera, assistant professor of entomology at AgriTech in CALS, collected the volatile compounds that emanate from apples – which include molecules that attract female codling moths, a major pest of all apples, pears and peaches. They then separated the mix of molecules found in apple odors using a technique called gas chromatography. 

Credit: Jason Koski/Cornell University

Next, they attached a female moth’s antenna to two electrodes on the electroantennogram and exposed it to each apple scent molecule. When an active molecule reacts with the antenna, it creates a small current that is recorded as a change in voltage. The researchers are using this technique to pinpoint a molecule that the female can detect and that may trigger a response. The strategy could lead to new lures that specifically target females. 

“We work with the pheromone industry and growers,” Duplais said. “As soon as we detect the right molecule, we can create the lure, test it in apple orchards, and if it works, make it commercially available.”

Duplais and Rivera, along with graduate students Mason Chandler and Sandra Lizarraga, both in Rivera’s lab, are also working to identify new pheromones with novel uses. This year, they identified a potential alarm pheromone produced by woolly apple aphid colonies and are testing whether it causes the aphids to disperse in apple orchards. The team is also investigating whether scent compounds produced when black stem borers tunnel in apple trees might also promote collective behaviors that could help trap them before they cause damage.