Research Projects Aim to Squeeze Out a Growing Threat to the Global Citrus Supply
Citrus industries are in trouble. Citrus greening disease could decimate groves in almost all of the world's major citrus growing areas, from Africa and Asia (where the disease originated) to Europe and South America. While research teams rush to pursue research and protection projects, no cure exists. (Because of a bacterium transmitted by a tiny insect commonly known as the Asian citrus psyllid, citrus fruit becomes misshapen and discolored and drops prematurely. Eventually, the trees die.)
In Florida, USA, citrus greening first appeared in 2005. By 2017, the state's citrus production had dropped by 75 percent. The disease now affects all of Florida's citrus-growing areas.
“It's a big problem,” says Bryce Falk, PhD, distinguished professor of plant pathology, University of California, Davis, Davis, California, USA. “When pathogens invade a new environment, they can take advantage of it, and that's what happened in Florida with its contiguous citrus and constant growth—it was a perfect environment.”
Project teams are searching for ways to stop or at least slow the disease. In March, fragrance and flavor manufacturing company Givaudan funded a US$3.5 million project at the University of California, Riverside that will build a protective screen to shield one of the world's most extensive collections of citrus, home to more than 1,000 variations. The collection, which was established over a century ago, is sometimes called the Noah's Ark of citrus: It houses two plants of every type of citrus in the world. Scientists use them to research citrus diseases and breed new varieties. Expected to be completed next year, the project will build a protective screen for new trees and backup plants across 2.8 acres (1.1 hectares) of the 22.3-acre (9-hectare) collection to keep the Asian citrus psyllid out, while allowing sunshine and water in.
Inspections at an orange grove in Fort Pierce, Florida, USA
PHOTO BY JOE RAEDLE/GETTY IMAGES
A US$7.3 million project, co-led by Dr. Falk and funded by the U.S. National Institute of Food and Agriculture, has been engineering plant and insect viruses and using them to target psyllids so that they cannot reproduce, cannot transmit the bacterium or simply die. Launched in 2015 with a slated 2020 completion, the project involves searching for viruses the team can genetically modify to kill, sterilize or neutralize psyllids.
To realize benefits, the project can't simply take place in a lab, sealed off from the people who ultimately will benefit from it. That's why two people from the 10-member project team are devoted entirely to outreach and communication, such as maintaining an educational website about the project and meeting regularly with citrus growers. The website, for instance, explains highly technical research in short snapshots, with the goal of helping the general public understand various research strategies and reassuring them that the problem is being exhaustively studied. “That outreach helps growers and regulators understand that we all need these projects,” Dr. Falk says. —Novid Parsi