Citrus Canker, A Disease that Attacks the Tree and Fruit – 1912

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Citrus is at war every day!  It must deal with the weather; dry springs; occasional freezes; hurricanes; and flooding in some areas.  It is also a target for many pests; insects, diseases, and weeds are always present.  Most of these pests can be dealt with by growers using cultural practices and pesticides.  Several pests can be extremely damaging and more drastic action is needed. 

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Citrus canker is caused by a bacterium (very small organism that can increase rapidly under wet warm conditions).  The disease primarily attacks the fruit and leaves producing raised ‘blister like’ lesions.  When severe, canker can cause defoliation and fruit drop.  Control of canker utilized a ‘seek and destroy’ approach.  Whenever an infected tree was found, it was destroyed as were trees surrounding the infected tree since they most likely had bacterium, but no symptoms.  This technique worked in 1912 even though it took 21 years for the state to declare the disease was eradicated!!  Fortunately, the disease did not spread very far during this time period. 

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Wind and rain were the primary means of moving the bacterium short distances.  The real problem with spreading the disease is people!  The organism can live for a while on clothing or harvesting equipment thus moving with the harvesters.  If infected leaves or fruit made it into boxes it could be moved great distances. 

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Canker appeared again in 1986 in Manatee Cunty and by 1994 it was thought to be controlled.  The next year, 1995 canker showed up in Miami and this time it moved quickly, especially in urban areas where homeowners had no idea what it was.  The state had a difficult time removing infected trees from backyards and the effort ended up in court.  Growers were fighting the disease using the ‘seek and destroy’ method used in the past, however in 2004/2005 several hurricanes spread canker to the point that it was no longer feasible to remove infected trees.

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Strict regulations are in pace to keep canker from being moved within and out of the state.  Growers can spray and removed infected tissue to keep the disease under control.  Even though we will not be able to eradicate this disease, we can manage it.  Another challenge facing the citrus grower.