To Ditch Pesticides, Scientists Are Hacking Insects’ Sex Signals

To Ditch Pesticides, Scientists Are Hacking Insects’ Sex Signals

Creamy-colored and just a couple of centimeters long, the cotton bollworm doesn’t look like much. But around the world, this highly mobile moth has farmers breaking out in a sweat. Females can lay hundreds of eggs at a time, which hatch into voracious caterpillars. They feast not just on cotton, but soybeans, tomatoes, sweetcorn, peppers, and many other crops, devouring flowers, reproductive tissues, fruits, and kernels. A harvest can be quickly decimated.

Every year, insects like the cotton bollworm destroy more than 20 percent of the world’s crops. Farmers fight back by using pesticides, but some are harmful to our health, and many damage surrounding ecosystems. Clearly, more environmentally friendly approaches to pest control are needed, and there’s one solution that could be about to hit the big time: targeting these pests’ sex drives. 

Female insects can attract partners in complete darkness without any audible signal, and over hundreds of meters—sometimes over a kilometer—using sex pheromones. Males track the smell of these chemical signals and mate with the females they’re led to, who then lay eggs that hatch into hungry larvae. It’s an incredible chemical power—and one that can be exploited.

“We can apply artificial pheromone compounds into the field, which will be released everywhere in the air and cover the original signal from the real female,” says Hong-Lei Wang, a researcher in the pheromone group at Lund University in Sweden. This blanket cover of the sex scent makes it harder for males to find females and mate, he explains, and so the insect population falls, meaning fewer pests in the area to cause crop damage.

Farmers have been using artificial pheromones this way for decades—but up until now, costs have limited how widely they’re used. Creating artificial pheromones has been pretty expensive, so it’s only made economic sense to use them to protect high-value crops, such as fruits. But now Wang and his colleagues have uncovered a way to affordably and sustainably produce pheromones that attract pests that eat cheaper crops, such as cabbage and beans, opening the door for pheromone-based pest control to be used more widely. 

In a paper published in Nature Sustainability, the group showed how to make significant amounts of two important moth pheromones from an oilseed plant. They then demonstrated that the artificial pheromones worked well in mass trapping experiments as well as in disrupting the mating of the cotton bollworm.

“The first thing was to work out the pathways for pheromone production in the insects,” says Christer Löfstedt, coauthor of the study and professor of functional zoology at Lund. This was done by looking at the insects’ genes to find the ones that control production of the desired sex pheromone. Then the group introduced these genes into a different biological platform—which in this study was the oilseed crop, though yeast would also work—so that it would make the sex pheromone at scale. Finally, the compound was isolated and purified to get it ready for testing in the field.

For the experiment, the new plant-derived pheromones were tested in the field using pheromone dispensers, with their effectiveness being compared against conventional synthetic pheromones. Both versions were equally effective in trapping insects and disrupting their mating, shown as a decline of the insects’ male population over time. This proved the plant-derived pheromone to be a viable alternative to the artificial pheromones traditionally used.


via Wired

November 23, 2022 at 04:09AM

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