Johnny Morgan, Singh, Raghuwinder
BATON ROUGE, La. – A new disease of citrus called citrus canker has been detected in New Orleans by the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, Plant Protection and Quarantine division, according to LSU AgCenter plant scientist Raj Singh.
“The disease was first detected in Florida in 1910, and after its initial detection, the disease was declared eradicated twice – in 1933 and 1994,” Singh said. Citrus canker was again detected for a third time in Florida in 1995.
Louisiana has become the second state after Florida in the United States where the disease is positively identified.
“It is a serious disease of citrus because it causes defoliation, premature fruit drop, blemished fruits and tree decline, and ultimately, the infected tree stops producing fruit,” Singh said.
Citrus canker is a bacterial disease thought to have originated in southeastern Asia.
“Different strains are known to occur in citrus-growing regions of the world,” he said. “But the Asiatic strain is considered to be the most severe and widespread form of citrus canker.”
All commercially grown citrus varieties, including grapefruits, lemons, limes, oranges, sour oranges and tangerines, are susceptible to this disease.
The pathogen can cause symptoms on all young, above-ground plant parts. Symptoms on leaves start as tiny raised blisters that may enlarge and become tan to brown as the disease develops.
“Lesions are visible on both sides of the leaves with water-soaked margins surrounded by a yellow halo,” Singh said. “As the lesion ages, the center becomes raised and corky and may fall out, giving it a shot- hole appearance.”
Similar lesions are present on the twigs but without the water-soaked margins and yellow halo. The pathogen forms raised corky lesions on the fruits with water soaked margins surrounded by yellow halo.
The bacterium enters the host tissue through natural openings and wounds. It is not spread by insects or other organisms, but the wounds caused by citrus leaf miner may serve as infection sites, Singh said.
Bacteria may survive in old lesions, and under favorable environmental conditions they may ooze from these lesions and disperse a short distance by wind and rain.
Long-distance movement of citrus canker is generally attributed to human movement of infected citrus material and storms such as hurricanes and tornadoes.
“We highly urge Louisiana residents to not move any infected citrus plant material within or out of state and to report any suspected trees to Bill Spitzer, state plant health director at email@example.com or 225-298-5410,” Singh said.
More information about citrus canker can be found by calling Singh at 225-578-4562.
The LSU AgCenter and the LSU College of Agriculture