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Tuesday, July 27, 2021

UCD researchers study ways to diminish impact of invasive pest

The male Japanese beetle doesn’t look for a pretty face when trying to choose a mate.

Instead, the invasive pest sniffs for a female’s sex pheromone, a chemical signal which she naturally releases, which the male detects with an enzyme in its antennae, said UC Davis entomology professor and chemical ecologist Walter Leal.

By inhibiting the male’s ability to sense this enzyme, the beetle may not be able to reproduce. Leal, in collaboration with fellow UC Davis ecologist Yuko Ishida, has yielded research results that may have discovered a way to block the pheromone.

Because of its immense, omnivorous appetite it is one of the most destructive pests in U.S. agriculture.

The beetle was first detected in the United States in a New Jersey nursery in 1916; it has now invaded at least 22 states, according to a UC Davis press release.

Leal said that there are more than 300 known plants that the beetle can devour – it even eats sushi.

“[The Japanese beetles] are unbelievable,” he said. “Some insects are so specific … they’ll eat only one or two plants, and if you give them something else, they’ll starve to death. But the Japanese beetle will eat almost anything.”

Their large appetite has made them a significant threat to crops everywhere, so extermination and population control of the pest are essential to the farmers they threaten.

Along with the help of various undergraduate and graduate students, Leal has devoted much time and effort to conducting kinetic studies on how a male beetle uses his enzyme to find a female.

After collecting 100,000 beetles and taking off their antennae, Leal and his team have managed to isolate and clone the enzyme that the male uses to detect the female’s sex-pheromone; they are the first group to ever do so.

Now, Leal would like to find a way to inhibit this enzyme to make it more difficult for the pest to locate a mate.

“We’d basically blindfold the males so that they can’t find the females.

We’re excited about this because this opens the door for the possible manipulation of this population,” he said.

In addition, Leal has found that not only can the male detect a female Japanese beetle’s pheromone, but he can also detect the sex pheromone of females of another related species, the Osaka beetle, using what Leal calls a “behavioral antagonist.”

In female beetles, the signal released is a pheromone-degrade enzyme, so-called because it diminishes the female’s sex pheromone as the male approaches her, he said.

When the male Japanese beetle detects a female Osaka beetle, it can’t degrade its pheromone as rapidly as that of a female Japanese beetle.

It shuts the male down, acting as a sort of stop sign, Leal said.

Leal said he also hopes that these findings will lead to more environmentally-friendly alternatives to insecticides, which tend to have environmental costs.

Leal’s findings have generated much excitement within the scientific community, and many are hopeful that his information could assist the agriculture industry. For a few days, the U.S. Department of Agriculture posted his research on their website. He will also be presenting his findings in Brazil to the congress of the Brazilian Society of Entomology.

“Understanding how insects detect chemicals is very cool in and of itself,” said Dave Wilson, professor of molecular and cellular biology at UC Davis. “[But] from a more practical point of view, disrupting feeding or mating responses is important to anyone who is bitten by a mosquito or has their tomato plant consumed by insects.”

Colby Schal, a professor in the department of entomology at North Carolina State University, said, “This contribution is of general interest to researchers interested in olfaction (studying the sense of smell) not only in insects but in all animals…. No other research group has carried out the thorough analysis conducted by Ishida and Leal.”

Leal said that he is fascinated by the interest generated by his studies, but emphasizes that he had a lot of help from students who spent hours at a time collecting beetles and antennae for no pay. He said that all their names are in the acknowledgements. And as for now, Leal plans to continue working on his research projects.

“[My research] was a milestone, but it’s not the end,” he said. “And that’s fundamental science. You prepare for the future.”

 

DANAI SAKUTUKWA can be reached at features@californiaaggie.com.

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