Environment & Science

Smelly fly traps offer hope for California citrus growers

This photo provided by the California Department of Food and Agriculture shows an Asian citrus psyllid (Diaphorina citri), an insect about one-eighth of an inch long. The insect is the carrier of a citrus disease that has killed millions of citrus trees and cost growers billions of dollars across Florida and Brazil.
This photo provided by the California Department of Food and Agriculture shows an Asian citrus psyllid (Diaphorina citri), an insect about one-eighth of an inch long. The insect is the carrier of a citrus disease that has killed millions of citrus trees and cost growers billions of dollars across Florida and Brazil.
Anonymous/AP

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Over the past few years, tiny invasive bugs called Asian citrus psyllids have spread through parts of Southern California, potentially endangering the state's $2 billion  citrus industry.

Scientists trying to curb these pests may have just gotten a whiff of victory, literally.

Researchers at UC Riverside have identified a series of naturally occurring smells that are extremely good at luring in these pervasive psyllids.

"We anticipate that this odor-based insect lure could be of use to growers in California and other parts of the world," project leader Anandasankar Ray said in a statement. Ray's research was published Monday in the the journal PLOS ONE. 

While citrus psyllids aren't a problem on their own, the bugs are a carrier for an incurable tree disease called Huanglongbing or citrus greening.

The sickness slowly kills citrus trees, turning their leaves yellow and leaving their fruit bitter and inedible.

Pysllids spread the disease as they travel to different groves. That's happened over the last decade in Florida where the citrus industry has suffered  $1.3 billion in losses.

So far, citrus greening has not spread widely in California, and growers hope to keep it that way by limiting the number of psyllids.

The smells identified by researchers as so alluring to these bugs are myrcene, ethyl butyrate and p-cymene. Asian Citrus Psyllids detect these odors using small "pit-like sensors" filled with neurons on its antenna.

Ray and his team analyzed numerous citrus smells to see which were most attractive to the bugs.

After narrowing in on these three, his team performed 10 weeks of field tests in El Monte to determine how effective the smells were at attracting the bugs to sticky traps.

Turns out, very effective. They blend of smells caught nearly 230% more psyllids than traps that did not contain the scents.

"What's particularly encouraging is that these three chemicals are affordable, useful in small quantities and safe for human handling," Ray noted.

This new powerful psyllid cologne could be used to develop traps to monitor the bugs spread.

The researchers also claim they can use a similar approach to one day develop smells that could block the psyllids' ability to sniff out nearby lemons, limes and oranges, effectively deterring them from spreading.

This is the latest in a string of efforts to detect and curb populations of Asian citrus psyllids. California is also backing the use of tiny wasps that feed on the psyllids as a natural means of population control.