AGRICULTURE

The fight to save a crop

ROBERT BLOCK November 19 1984
AGRICULTURE

The fight to save a crop

ROBERT BLOCK November 19 1984

The fight to save a crop

AGRICULTURE

In the past three months work gangs have visited 55 tree nurseries in central Florida, burning more than five millon young fruit trees in a desperate attempt to contain a deadly virus which is menacing the state’s $2.5-billion citrus industry. Florida state scientists know that similar strains of citrus canker, a highly infectious bacterial disease, have devastated orange groves in Southeast Asia, China, Japan and South America during the past 10 years. And no one has found a cure for the canker, which, although harmless to humans who eat the infected fruit, kills trees. The stringent measures undertaken so far—including a ban on the sale or movement of Florida-grown fruit within the state—has kept the disease from mature groves of fruit-bearing trees, but some scientists are convinced that the long-term solution lies in developing trees more resistant to canker. Declared Garrison Wilkes, a biologist at the University of Massachusetts in Boston: “What has happened in Florida is that they have a high-quality citrus with a narrow genetic base and they are caught—there is no resistance to this virus.”

However, finding genes resistant to canker could be difficult. Modern varieties of grapefruit, oranges and lemons derive much of their appealing taste from wild fruit strains found in China and Southeast Asia and imported to North America. But encroaching development and the substitution of higheryielding hybrid citrus species developed in North America have eliminated many of those primitive citrus strains in their native habitats. Government departments, including the United States department of agriculture, maintain collections of traditional seeds. Yet Wilkes, for one, wants to see many more scientific expeditions to remote areas to add wild plant genes to existing stocks.

Indeed, strengthening the gene banks that already exist is only the first step to such agricultural crises as the canker threatening Florida’s 67 million citrus trees: even if scientists find a gene that will produce canker-resistant fruit trees, it could take as long as 20 years before they are available to citrus growers. Said Wilkes: “These vulnerabilities are inherent in the agricultural system. All you can do is have an active research program.” -ROBERT BLOCK