Texas growers take aim at greening disease

11/25/2013 03:06:00 PM
Tom Burfield

The Asian citrus psyllid as well as citrus greening disease, formally known as huanglongbing, have been detected in Texas, but growers have taken steps to keep the disease and its vector under control.

As of mid-November, Texas had two quarantine zones where the disease had been found, said Ray Prewett, president of Mission-based Texas Citrus Mutual.

One was a 5-mile radius around San Juan, which has been in effect for about two years. The other was established in October in Mission.

The San Juan find was in two commercial groves, one across from the other. The find in Mission was in a residential area.

About 1,760 acres have been quarantined in Mission, and slightly fewer in San Juan.

If an area is under quarantine, growers must spray their groves shortly before harvest to kill as many psyllids as possible.

During harvest, they must follow appropriate procedures for removing leaves and plant material.

Mission-based TexaSweet Citrus Marketing Inc. recently launched a major outreach effort for homeowners that includes radio advertising and extensive mailings to make residents aware of the situation, he said.

Texas growers have been participating in an active area-wide Asian citrus psyllid control program for four years.

Under the program, growers spray their acreage during the dormant time of the year, when the number of psyllids is at its lowest. All growers in each of three specific growing areas must spray during short windows in November and in January/February to help reduce the psyllid population.

Prewett estimated that 85% of commercial acreage in Texas is treated during the dormant period under the areawide management program.

“We’re doing everything we can to bring the psyllid population down,” Prewett said.

Nearly all of the infected trees in the state have been removed, and the state has implemented a nursery program where new regulations will require all production nurseries to grow trees in an enclosed environment, he said.

A biological control program also is being ramped up using Tamarixia wasps brought from Pakistan as parasitoids that will attack the psyllids.

“It is a good program to bring down the population of psyllids in urban areas,” Prewett said.

That program will not be sufficient to get the population as low as it needs to slow the spread of the disease, which is the objective.

So far, the disease has been identified in fewer than 100 trees in Texas.

The wasps can’t yet be used in commercial growing areas because routine spraying could kill them, he said.

Something new in Texas from the U.S. Department of Agriculture Animal and Plant Health Inspection Service is a field insectary program, where existing psyllid-infested trees are caged, and Tamarixia are introduced and allowed to reproduce, Prewett said.

The Tamarixia population multiplies, the cage is removed after a couple of months, and the insects self distribute.

The state also is in the process of creating the Texas Citrus Pest and Disease Management Corp. to deal with HLB and the psyllids, Prewett said.

The body has been authorized by the Texas Legislature, and a 15-member board of directors will conduct a referendum to seek approval by growers.

Texas has about 27,000 acres of citrus, 70% of which are grapefruit, and 30% of which are oranges.



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