Citrus canker, greening continue to spread in Louisiana

By Nikki Henderson |

Published 07/08 2014 04:38PM

Updated 07/08 2014 04:42PM

Citrus harvest is still months away, but this year's crop in Louisiana faces two growing threats citrus canker and citrus greening.

Citrus canker, an incurable bacterial disease, was recently found in St. Bernard Parish, said Raj Singh, director of the LSU AgCenter Plant Diagnostic Center. It is present in four other southeastern Louisiana parishes, including Plaquemines, which produces the most citrus in the state.

Singh said the canker bacterium causes lesions on all above-ground plant parts, including fruit and leaves. Fruit with canker lesions loses its market value, and, ultimately, infected trees stop producing fruit.

All citrus varieties are susceptible. The canker is highly contagious and warm weather, rain and wind cause it to spread even faster.

Singh said, "It is going to continue to spread in Louisiana because we have the right weather conditions."

The disease was first detected in Louisiana in 1914, but was eradicated by 1940.  In June 2013, citrus canker resurfaced in Louisiana.
Singh said inspectors with the Louisiana Department of Agriculture and Forestry will collect samples from suspected trees in citrus-producing parishes that he will test. While there is not much that can be done once a tree is infected, LDAF quarantines will be put in place to control movement of affected plant material, including fruit.

Singh expects the canker's growing presence to have a bad effect on this year's citrus harvest. Fruit from infected trees is safe to eat but difficult to sell because of the unsightly lesions and restrictions from quarantines.

Unfortunately, another incurable bacterial disease called citrus greening was detected in the New Orleans area in March, Singh said. Citrus greening is spread by the Asian citrus psyllid insect. Infected trees produce green bitter fruit and can eventually die.

To help identify these diseases, Singh conducted training sessions for 15 extension agents from southeastern and southwestern Louisiana on May 29 and June 9 in New Orleans. The agents studied trees that exhibited symptoms of citrus canker and citrus greening.

Singh said, "The symptoms produced by citrus greening are somewhat similar to nutritional deficiencies and can easily be misdiagnosed. Citrus greening is confirmed by molecular analysis, but if the agents are familiar with the symptoms, they can easily screen them for their constituents."
Singh also said similarly, a fungus called greasy spot may be easily confused with citrus canker, Singh said. The training provided agents experience in identifying both diseases in the field.

In 2013, the Louisiana citrus industry was valued at $5.4 million. There are more than 400 producers in the state.

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