Rod Santa Ana

October 14, 2009

4 Min Read

A conference to address serious plant diseases in citrus and potato crops is drawing national and international attention, according to organizers.

The conference will bring together researchers and industry leaders affected by what’s commonly known as citrus greening disease (Huanglongbing) in citrus and zebra chip disease in potatoes, said Ray Prewett, president of Texas Citrus Mutual in Mission.

The conference, officially known as the “Citrus Huanglongbing and Potato Zebra Chip Conference: Status of Diseases and Research Opportunities,” will be held Nov. 16-18 at the McAllen Convention Center, 700 Convention Center Blvd., in McAllen.

Early registration fee is $175 through Oct. 15. The fee for registration from Oct. 16 to Nov. 6 is $225.

“These diseases in potatoes and citrus are already causing serious economic losses in areas where they are established, and they are of great concern to areas threatened by them,” Prewett said.

The conference has generated interest from scientists, producers and industry leaders in Texas, California, Florida, Arizona, Louisiana, Mexico and Belize.

U.S. Department of Agriculture officials from Raleigh, N.C., and Beltsville, Md., are also expected, Prewett said.

“As word about this conference gets out, we’re expecting interest from other areas as well,” he said.

Prewett said the decision to address diseases in two very different crops was based on scientific and practical motives.

“Both diseases are spread by related insects called psyllids and are caused by related bacteria,” he said. “Both are incurable and are causing or threatening to cause significant losses to these two vital crops.”

Prewett said the practical reasons include the fact that many scientists are researching both diseases; the gathering will give them the opportunity to network and compare notes.

Dr. John da Graca, director of the Texas A&M-Kingsville Citrus Center at Weslaco, said the consequences of citrus greening are disastrous.

“Many immature fruit fall off infected trees, while remaining fruit are lopsided, remain partially green, hence the term ‘greening,’ and taste bitter,” he said. “Symptoms spread throughout the tree which slowly declines and can eventually die.”

The disease was first reported in a scientific paper in India in 1927 but may have been present since the 18th century, he said.

“It spread by movement of infected plants throughout south and southeast Asia during the 20th century, was confirmed in Brazil in 2004 and in Florida in 2005.”

The disease has been devastating for the Florida citrus industry, where more than one million trees have been removed as part of the effort to control it, da Graca said.

It has since been found in dooryard trees in Louisiana, Georgia and South Carolina. It is also widespread in Cuba and has recently been found in Belize and the Yucatan state in Mexico.

“Texas citrus is now seriously threatened by this disease,” he said.

Greening’s vector, the Asian citrus psyllid, was found in Florida in 1998 and appeared in Texas in 2001, where it has been detected in over 50 counties across the southern half of the state, da Graca said.

Psyllids spread to California in 2008 but so far, greening has not been detected in psyllids or plants in either California or Texas.

“At this conference in McAllen our citrus greening discussions will focus on symptoms, surveys, psyllid control, regulations and other management strategies,” he said.

Dr. Dennis Gross, a Texas AgriLife Research plant pathologist, coordinates a team of researchers studying zebra chip in potatoes with a grant from the Texas Department of Agriculture.

“Zebra chip is a bacterial disease that alters the sugar levels in potatoes that caramelize when chips are fried, causing an off-taste and a burnt appearance,” he said. “The disease is spread from plant to plant by the potato psyllid, an insect that injects the pathogen into uninfected plants as it feeds on leaves.”

Zebra chip first appeared in Mexico in the mid-1990s. In the was first reported in Texas in 2000 in potato fields throughout South Texas and the Rio Grande Valley. Most recently it has been detected in the South Plains and Panhandle regions.

“Chipping potatoes are grown throughout the U.S., and the disease has the potential to cause serious economic losses throughout the country unless we find some way to control the spread of the pathogen and its psyllid vector,” Gross said.

Conference topics on zebra chip will include the latest information on disease management and control of psyllids, detection and spread in the field of the pathogen and the development of disease resistant cultivars, he said.

For more information, or to register for the conference, visit either the AgriLife Extension Web site, or the Texas Citrus Mutual Web site.

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