By Len Wilcox
University of California Davis (UC Davis) researchers have identified the sex pheromone of the Asian citrus psyllid (ACP), a discovery which will lead to better methods of controlling the pest. The ACP is a major threat to citrus around the world. The psyllid is a tiny insect with the potential to wreak havoc as it spreads the bacteria that causes huanglongbing (HLB), also known as citrus greening disease.
The sex pheromone can be used as a lure for trapping, which will dramatically improve capture of this psyllid with conventional sticky traps. This is major progress toward integrated pest management of the insect.
The ground-breaking discovery, encompassing six years of research, was made by an international team of scientists led by UC Davis chemical ecologist Walter Leal. A native of Brazil, Leal announced the discovery during his presentation in December at the annual Brazilian Meeting of Chemical Ecology. His team included scientists from UC Davis, University of São Paulo and Fundecitrus of São Paulo.
“This project was a collaboration of three institutions, with UC Davis taking the lead. We have been at work on this project for six years because this is a very complex insect and its behavior is very complicated,” Leal said.
Leal’s specialty is the biochemical and molecular basis of insect olfaction. “Research in my lab is aimed at unraveling the molecular mechanisms that make the insect’s olfactory system so sensitive and selective.”
BEGINNING WITH BASIC BIOLOGY
The research project started with very little established information about the biology of ACP, and what information researchers did have was confusing and sometimes contradictory.
“We had to study the basic biology of the insect first,” Leal said. “It took a long time because nothing was known about the biology, so we did not have reliable information to get started with.”
Not having much information available meant that he had to start the research at a basic level.
“We had to establish a new colony of ACP insects that were collected in Brazil,” Leal said. “And we started studying the basic biology of that group of insects to see how they behaved, and what time the female was producing a pheromone and what was the best age to copulate. All of this is basic information, normally available at the start of a project of this nature.”
After collecting and analyzing the basic biological data, the study looked at more complex matters.
“Then we moved on to the behavior and began to identify the sex pheromone and how the insect used it,” explained Leal.
The pheromone will be used as an aid in surveillance. It will be applied as a lure to attract the insects to a trap, which will allow scientists to monitor the population of the insects in a specific area. Then, the trapped insects can be tested to determine if they are infected with the HLB bacteria or if they are free of disease.
Leal pointed out that this discovery, while important, is just the first step in identifying better ways of controlling HLB-infected psyllids.
“There is also a possibility in the future that the pheromone may be used in an insecticide … instead of spraying a whole field, we use a little of this pheromone mixed with an insecticide,” Leal said. This strategy, if successful, would utilize less pesticide but control insect populations over a large area.
“This was a breakthrough as nothing was available (as an attractant),” said Leal. “Now we have this attractant, but there is a possibility we can find even better attractants, so we are not going to stop. We are going to continue the research in parallel with development of this formulation to see if we can get an even better attractant than the one we have so far.”
He added, “It is true that we are never too happy with what we have. We always want something more. This research is especially important not only in California, Florida and Brazil, but in China and many other countries,” since HLB is a worldwide infestation. “So the better the formulation, the better the attraction and the higher the chances that this is going to be successful.”
Len Wilcox is freelance writer in Sanger, California.
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