Editor's Note: This is the Field Notes column, written by editor Vicky Boyd and published in the September-October 2011 issue of Citrus + Vegetable Magazine.
A citrus grower chided me recently about not including the disease, citrus blight, in an article, saying I intentionally ignored the malady.
I responded that I had no problems writing about citrus blight, but I thought including it would not enhance the article and could possibly be confusing.
But his comments started me wondering why the research community has not focused more attention on citrus blight, a problem that’s been around for at least a century and results in the loss of more than 900,000 bearing citrus trees annually.
This is a disease that reduces a tree’s ability to take up water, resulting in wilt, twig dieback and chronic decline. Other than through root grafts, the exact transmission route is unknown. The exact cause also remains a mystery.
Some claim it’s merely a rootstock problem since sweet orange, sour orange, Cleopatra mandarin and until recently, Swingle citrumelo, appeared to be more tolerant of the problem.
But Swingle, which has several positive attributes, now appears to be less tolerant than originally thought. And groves planted on the popular rootstock are succumbing to blight.
Even as recently as the mid-2000s, at least one team of researchers was delving into citrus blight.
A group led by Ken Derrick, a plant pathologist at the Citrus Research and Education Center, spent six years and found some evidence that Idaeovirus, possibly in association with citrus tristeza virus, could be linked to citrus blight.
But to confirm their hypothesis would take several more years of research. Their findings came about the same time that greening began to rear its ugly head, so any further research was put on the back burner.
I agree that citrus greening, also known as huanglongbing or HLB, is a more pressing problem. But the citrus industry shouldn’t totally turn its back on citrus blight, a disease that causes growers to remove nearly 1 million trees annually.
Earlier this summer, Bob Norberg, deputy executive director of research and operations for the Department of Citrus, told growers attending the Citrus Industry Conference that the demand for orange juice is growing worldwide.
Just in the United States, he expects orange juice demand to grow by 500 million single-strength-equivalent gallons by 2030.
To capitalize on it, he says Florida needs to plant 30 million citrus trees during the next 20 years. At the same time, growers are losing 2 million, or 4 percent of their plantings annually. And Norberg expects losses to grow to 4 million trees annually by 2025.
Citrus blight will be another hurdle that growers will need to clear—blindly in this case—if they want to take advantage of burgeoning worldwide orange juice demand.
The disease needs research attention at a level that will help unravel some of the mysteries of what has been called young tree decline, sandhill decline, roadside decline and rough lemon decline.