A recent article in the New York Times called “A Race to Save the Orange by Altering Its DNA” tells the story of citrus greening disease, which is destroying citrus trees in Florida. The disease is spread by an insect, the Asian citrus psyllid, an invasive species which was first detected in Florida in 1998. By September of 2000, the pest had spread to 31 Florida counties, and today it can be found in Alabama, Arizona, California, Florida, Georgia, Guam, Hawaii, Louisiana, Mississippi, Puerto Rico, South Carolina, Texas, and the U.S. Virgin Islands.
Citrus greening disease, also known as Huanglongbing, is devastating the Florida citrus industry. The disease is found in all of Florida’s 32 citrus-producing counties and can kill a tree in two years, threatening the state’s $9 billion citrus industry and 76,000 jobs. To fight the disease, $11 million in federal money has been secured for research, and the state of Florida has approved $9.5 million. According to the University of Florida’s Department of Entomology, diseased trees show “stunted growth, sparsely foliated branches, unseasonal bloom, leaf and fruit drop, and twig dieback. Young leaves are chlorotic, with green banding along the major veins. Mature leaves have yellowish-green patches between veins, and midribs are yellow. In severe cases, leaves become chlorotic and have scattered spots of green. Fruits on greened trees are small, generally lopsided, underdeveloped, unevenly colored, hard, and poor in juice.”
In the Times article, Ricke Kress, the president of Southern Gardens Citrus which owns 2.5 million trees and produces oranges for Tropicana and Florida’s Natural, is trying to beat the disease by genetically modifying the orange trees so they become resistant to it. Erik Mirkov of Texas A&M University may have found the answer by using a gene from spinach that produces a protein that attacks invading bacteria. So far the results look promising: “In an infection-filled greenhouse where every nontransgenic tree had showed symptoms of disease, Dr. Mirkov’s trees with the spinach gene had survived unscathed for more than a year.”
However, they will have to clear regulatory hurdles, which will take a couple of years at least.