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January 24, 2011

Bacteria killing citrus trees is bigger threat to juice industry than cold weather, say US farmers

by Tamara Lush

While Florida farmers have lost much of their crop to cold weather for the second year in a row, they say a fast-spreading, incurable bacteria presents a greater threat to their trees and the citrus industry.

Citrus greening has destroyed groves in the U.S., Brazil, Asia and Africa. Detected in Florida in 2005, it leaves fruit sour, malformed and unusable. Eventually, it kills the tree.

The disease has been particularly devastating because it takes years for citrus trees to reach peak production, and the disease targets young trees, making it difficult for growers to replace those that have been lost.

"It's probably is one of the biggest negative impacts in Florida today, short of the housing collapse," said Louis Schacht, a Vero Beach farmer whose family has grown oranges for 60 years.

Trees don't pass the bacteria to each other. Instead, greening — also known as yellow dragon disease, HIB or, in Chinese, Huanglongbing — is spread by insects. There is no cure.

Hundreds of researchers from more than a dozen countries converged on Orlando last week to talk about the disease and hear the latest research. They found hope in one announcement: A University of Florida-led group of international scientists has assembled the genome sequences for two citrus varieties — sweet orange and Clementine mandarin — in an effort to determine why trees are so susceptible to greening. Eventually, they hope to engineer varieties that aren't.

"There is nothing we have today that is effective against the bacteria," said Dan Gunter, chief operating officer of the Citrus Research and Development Foundation Inc., which funds research on greening and other citrus issues.

Two percent to 3 percent of Florida's citrus trees die in a typical year because of things like cold weather, bugs or old age. But since greening emerged, 4 percent to 5 percent have been lost each year, experts said.

Since most of Florida's oranges become juice, while California mainly grows those found in lunch boxes, greening could eventually affect consumers at the breakfast table.

"Greening means lower availability of juice, more uncertainty of juice supplies," said Bob Norberg, the deputy executive director of research and operations at the Florida Department of Citrus.

Analysts say shoppers can already expect to pay more after a hard freeze damaged one-third of Florida's early orange crop varieties and nearly half of the midseason crop this year.

Replacing trees killed by greening has proved costly and, in some cases, futile. Young trees need irrigation and expensive fertilizer and take time to grow. In their early years, they produce less fruit than older trees. And, in a cruel twist of fate, young trees appear to be the most susceptible to the insect that transmits the greening bacteria.

"The insect that transmits the disease generally is looking for new growth on a tree," Norberg said. "Young trees are all new growth and that insect is more attracted by younger trees."

At Schacht's grove on Florida's east coast, the smell of sweet juice fills the air as he packs fat honeybell tangelos, navel oranges and ruby red grapefruit into boxes for customers across the United States. In the nearby retail store, Schacht's father serves slices of the citrus and little cups of juice to visiting tourists.

The family farm sits in the middle of the so-called Indian River growing area, which stretches from coastal Palm Beach to Daytona Beach and 20 miles inland. It's the biggest orange and grapefruit growing area in Florida, contributing a sizeable chunk to the state's $9 billion citrus industry, and farmers say the calcium-rich soil and tropical breezes make their fruit especially tasty.

Schacht, however, worries about his and other growers' future in the area. Like most other farmers, he first learned of greening in 2005 and, shortly afterward, found it in a 3-year-old Valencia orange tree. Since then, 40 of his 280 acres of trees have been affected.

Scientists say the bacteria and insects responsible for greening entered the U.S. in Miami-Dade County and spread north. Schacht's groves were in the path.

"It's hard to identify," said Schacht, pointing to a scraggly tree with yellow leaves and puny, green oranges. "It affects the leaves first, they have a blotchy yellowness. A lot of times, it's mistaken for a nutrient deficiency."

Some farmers are trying to control the disease by using certain combinations of nutrients. Meanwhile, Schacht shakes his head and says he's not sure what to do about the 40 acres he's lost. He doesn't want to spend the money on new trees, irrigation and fertilizer, only to lose them to the disease again.

"When you see what it does to a tree, it's pretty bad," he said.


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