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Second greening case in two years not a cause for alarm in Texas' Rio Grande Valley region

In January 2012, Texas officials found the first confirmed case of huanglongbing — HLB or greening disease — in a grove near San Juan, TX. In October, a second case was confirmed in nearby Mission, TX.

The second discovery is not cause for alarm and in fact in some ways can be seen as a victory. While greening has decimated the Asian and Brazilian citrus industries and has destroyed thousands of trees in Florida, a coordinated approach to spraying for the psyllid that spreads the disease has kept it at bay to date in Texas.

Greening-2Eric Mirkov added two spinach genes to citrus stock to create varieties that are seemingly impervious to greening. (Photo courtesy of TAMU)The vast majority of the Texas citrus crop is unaffected by either outbreak and there are quarantine zones in place to prevent further spreading.

Madhurababu Kunta, who runs the lab at the citrus center, said it processes more than 100,000 insect samples per year and nearly as many plant samples. New semi-automated machinery purchased in the last year has been able to extract and evaluate more DNA samples, making identification of "hot" psyllids and infected trees a much more efficient process.

About 80 trees have been removed from the San Juan grove, which is a commercial operation. The latest confirmed case is in a backyard grapefruit tree - which was removed -- in Mission.

In fact, homeowners with citrus trees are a larger concern now than commercial groves for possible contamination. While growers coordinate spraying and take other measures to prevent HLB, homeowners do not.

The latest outbreak also points out that HLB can lie dormant for years before rearing its ugly head. There is no way to know how long any of the impacted trees in Texas were infected.

The citrus industry and local governments are reaching out to homeowners to make them more aware of HLB and signs to look for. The industry, meanwhile, is purchasing its new stock from indoor nurseries to avoid potentially exposed plants.

Meanwhile, the US Department of Agriculture has also intervened, releasing thousands of Pakistani wasps - a natural predator that feeds on the psyllids -- each month from a location in Edinburg, TX. Texas A&M scientists are also studying a fungus that feeds on the psyllid for possible use in the field.

A&M researcher Eric Mirkov recently made the staggering discovery that citrus cultivars crossed with genetic material from spinach are, seemingly, wholly resistant to HLB. It is a find that could literally alter the course of history and certainly of the citrus industry.

No, the spinach genes do not affect the taste, shape, appearance or color of citrus grown on trees that include its DNA.

"Those are the top questions I'm asked," Mirkov laughed. "Will my orange juice be green? Will it taste like spinach?"

Public response to the hybrid fruit has been generally positive but the new varieties are undergoing thorough vetting by the federal Environmental Protection Agency. Even though the new citrus cultivars are a cross between two commonly accepted, undeniably safe food products, they must still go through the same rigorous testing as any genetically modified crop.

"We've really got something solid here. We've got something in hand, it works. But we've got a big challenge ahead of us with getting through EPA," Mirkov said. "It's good, it's great, it's necessary to regulate and make sure it's safe. But we kind of thought, 'Look, it's spinach, everyone eats spinach, there are no known allergies,' so we thought we might have an expedited path through. But we might as well have invented a new type of warfarin or rat poison and put it in citrus. We have to do basically the same thing that a manufacturer would do if they came out with a new fungicide. This is all very time-consuming, it's all very expensive - as a scientist I'm frustrated. It has to be done but I wish with something so important that there might be ways to do this faster. But it's just not possible. I get a lot of farmers who say, 'I'll just call my congressman.' Well that doesn't work either. The rules are the rules that are set in stone and we've got to do it."

Still, "History repeats itself. When HLB shows up somewhere, it's always the same,"Mirkov said. "We're hitting this hard and we're doing everything we have to do and we hope to have gone through the regulatory process and finished it and been okayed by late 2016. But it's going to take time to build up trees and get trees out there."