Deadly Disease Poses Threat to California Citrus

Deadly Disease Poses Threat to California Citrus

A wise person once said that to be forewarned is to be forearmed, and that’s particularly true when it comes to a new disease threatening our state’s citrus crops. The disease is called Huanglongbing (HLB), and is sometimes referred to as “citrus greening disease” or “yellow shoot disease” and has the potential to cause extensive damage to California’s nearly $2 billion citrus industry and the jobs that depend on it.

This disease got its initial US foothold in Florida around 2001, and since that time has decimated the citrus industry in the Sunshine State. Prior to the infestation, Florida had approximately 1 million acres of citrus trees planted. Today, that number has been reduced to approximately 400,000+ acres. From there, HLB has spread west, and was spotted in 2012 on a backyard lemon tree in Southern California, according to the Citrus Research Board’s web site.

citrus-deseaseHLB takes about a year to visually manifest itself on a tree. One of the early signs that a tree is infected is yellowing leaves, which looks somewhat similar to a vitamin deficiency, thereby making early identification tricky for the backyard gardener. Once a diseased tree begins bearing fruit, it’s all too obvious that something has gone terribly wrong: the fruit is misshapen and bitter, small in size, and drops from the tree prematurely in large numbers. Worse yet, there is no known cure for HLB and the tree will eventually (and prematurely) die.

HLB is transmitted by the Asian citrus psyllid (ACP), so stopping the psyllid is crucial to halting the spread of HLB. According to the US Department of Agriculture, HLB has been found in Florida, Georgia, Louisiana and South Carolina, as well as Texas, Arizona and California. The Asian citrus psyllid has the ability to fly “for miles,” according to Elizabeth Grafton-Cardwell, Ph. D., a research entomologist at the University of California, Davis. Unchecked, a psyllid population that carries the HLB bacteria has the ability to decimate the entire citrus industry in the US.

How to Identify the Pest
The Asian citrus psyllid, Diaphorina citri, is a sap-sucking aphid-sized insect that feeds on stems and leaves of citrus trees and is the vector for transmitting HLB. This pest can be found in the newest growth or “flush” of the season. Although difficult to observe with the naked eye, the Asian psyllid can be seen with a magnifying glass.

Bacpadulteth Grafton-Cardwell, Ph.D., explains how to monitor citrus trees for Asian citrus psyllid: “The best way to detect the psyllid is by looking at tiny new leaves (feather flush growth) on citrus trees on a monthly basis. Mature citrus trees typically produce most of their new growth in the spring and fall, but young trees tend to produce flushes of new growth periodically during warm weather. Slowly walk around each tree and inspect the flush growth. Look for signs of psyllid feeding and damage, including twisted leaves, waxy deposits, honeydew, sooty mold, and adult psyllids.”

Once a citrus tree is infected with HLB, it’s too late to save the tree. The tree must be destroyed in order to prevent further spread of the diseased pest. The University of California at Davis offers excellent information about HLB and the Asian citrus psyllid as does the California Citrus Threat web site.

How You Can Help
Monthly inspection of your citrus trees is strongly advised. If you have reason to suspect your tree is infected, immediately call the California Department of Food and Agriculture hotline at 1-800-491-1899. If quarantines are put into effect in your area, take it seriously. Don’t move citrus plants, plant material or fruit in or out of the quarantine area or across state or international borders. With springtime around the corner and you’re planning to  plant citrus on your yard or garden, make certain you purchase “registered budwood” that comes with source documentation. It’s also advised that you dry out or double bag plant clippings prior to disposal.

Keeping this pest out of our area protects our food supply as well as the industry that employs many Californians. HLB is serious business, so let’s treat it that way.

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