Farmers in the major U.S. citrus-producing regions—Florida, California, Texas and Arizona, in particular—are facing a plague of epic proportions.
Oranges and a range of other citrus fruits are being decimated by an incurable disease, a lethal, bacterial infection known as “citrus greening”—or Huanglongbing.
It is spread by a tiny insect, the Asian citrus psyllid, which has just been found in San Mateo County, just south of San Francisco. In response, county and state officials have launched a surveillance and treatment program and introduced a quarantine of citrus trees and plant material.
Citrus greening is insidious. It blocks the flow of nutrients through the tree, a silent killer. In the final stages, an infected tree shows yellowed, mottled leaves and green, bitter, unusable fruit. Left alone, the tree will die within five to seven years.
The disease was found in South Florida in 2005 and has spread throughout the state. It has also been found and quarantined in California’s San Joaquin Valley’s citrus belt, a threat to the state’s $3 billion-a-year citrus industry.
There’s good news from the lab, however. Researchers at the University of Florida’s Institute of Food and Agricultural Sciences have hit the trifecta; they’ve developed genetically engineered citrus trees that show not only resistance to greening but also to canker and black spot, two other perennial problems for citrus producers.
The “cure” developed by the plant biologists is ingenious. They inserted a gene isolated from the Arabidopsis plant—a member of the mustard family—to create enhanced resistance to greening and reduced disease severity. Several trees remained disease-free after 36 months in a field with a high number of diseased trees.
Nevertheless, it will be a decade or more before these disease-resistant trees have received regulatory approvals, been planted widely and are yielding fruit. Until then, there is only one effective treatment: A soil drench of neonicotinoid (neonic) pesticide—derived from the naturally occurring nicotine found in plants—at the base of the young citrus tree’s trunk. This enables the chemical to be taken up through the roots, which keeps it from affecting other flying insects or pollinators, as spraying can.
Environmental activists have spent several years and many millions of dollars campaigning to ban neonics, claiming that the insecticide is responsible for catastrophic honeybee population declines.
Citrus growers are also concerned that the public might be resistant to the concept of genetically engineered fruit, even though virtually all of the foods in the North American and European diets have been modified in some way.
Plant varieties that could not and do not exist in nature have been created by breeders since the 1930s using “wide cross” hybridizations in which large numbers of “alien” genes are moved from one species or genus to another. These show up in common varieties of corn, tomato, potato, sweet potato, oat, rice, wheat and pumpkin—hardly fearsome “Frankenfoods.”
If juice from genetically engineered fruit is far cheaper than the alternatives—especially since the appearance and taste will be the same—consumers are likely to purchase it.
The fact is that just as there are no effective “natural” solutions to treating cancer or rheumatoid arthritis, there is no “natural” or “organic” remedy for citrus greening.
The long-term solution lies with genetic engineering. Meanwhile, if we don’t want to condemn the U.S. citrus industry to extinction, we need state-of-the-art neonicotinoid pesticides.