By Karen McEver

International scientists and researchers met Nov. 7-11 in Orlando for the International Citrus Canker and Greening Research Workshop sponsored by Florida Citrus Mutual. Attendees, with particular expertise in citrus canker and greening, shared their collective knowledge and addressed the current situation in the state.


Greening management

Huanglongbing, commonly referred to as citrus greening, was found in south Florida in August. It has been determined that greening has been present long enough to become well established, making eradication unlikely.

Results from the workshop included a number of management options to control the disease. Of utmost importance is the development of protocol to ensure a disease-free budwood source. Further, citrus nursery production must be enclosed and away from groves.

Because greening is carried from one plant to another by a tiny insect vector, the citrus psyllid, researchers stress the importance of keeping nursery and young trees psyllid free. At the same time, fruit-bearing trees should be sprayed at strategic times to prevent infestations.

Greening is extremely difficult to diagnose, so researchers will work to develop faster detection methods. And, more work needs to be done to determine the distribution of greening in Florida, as well as to identify the full host range of noncitrus plants.

In the long term, researchers will work toward vector (psyllid) control measures and transmission and sources of disease resistance.


Canker goal: eradication

Since canker was discovered in Florida nine years ago near Miami International Airport, the primary citrus industry objective has been total eradication of the bacterial disease.

The canker eradication program operating under Florida statute requiring the removal of canker infected trees and all trees within a 1,900-foot radius has marked for destruction or has destroyed more than 70,000 acres of commercial citrus trees. Most of that destruction — about 55,000 acres — has occurred within the last year as a result of the overwhelming spread of the disease caused by the 2004 hurricanes.

During September, the incidence of canker discoveries began to decrease and it was hoped that the eradication program would get ahead of the curve. Then, late into this year’s hurricane season, Wilma struck, leaving growers and researchers extremely concerned.

Researchers agreed that delays in the eradication program imposed by residential litigation and the year’s catastrophic storms were major setbacks.

A number of management options were identified, including the need to develop a new citrus nursery industry away from citrus producing areas and develop faster ways to detect and remove infected and exposed trees. Additionally, a new management tool may be defoliation of exposed trees.

Researchers indicated new introductions of canker appear to be the result of illegal plant introductions in the private sector, therefore, increased monitoring of plant movement is recommended. 

In the field, it is suggested that better sanitation protocols be in place for all components of the industry. 

One of the most important research priorities is the progress on the early development of canker resistant varieties. The development of resistant strains of citrus may hold the key to combating canker over the long haul.

Additional information resulting from the workshop emphasized that the canker situation in Florida is different from that of 1912 and 1986 when canker was eradicated. The exotic pest called Asian citrus leafminer has forever changed the epidemiology of canker in Florida for the worst, say scientists.

Lastly, researchers are evaluating the transition from eradication to suppression from a scientific perspective. In that scenario, the disease will dictate the use of resistant varieties, windbreaks, copper sprays, leafminer management, etc., as informed by ongoing research.

If, as feared, Wilma has spread the disease beyond the probability of eradication, then a program designed to suppress the spread of canker would be the next step. Time will tell.


Box-tax case resolved

On Nov. 16, the Florida Department of Citrus emerged the winner after three years of litigation brought about by six growers who challenged the department’s generic advertising and the supporting tax as violating their Constitutional First Amendment rights.

In March 2003, Florida’s 10th Circuit Court found in favor of the plaintiffs. The ruling was upheld by the Second District Court of Appeal in October 2004. While the case awaited a ruling from Florida’s Supreme Court, the U.S. Supreme Court ruled in Johanns, Secretary of Agriculture, v. Livestock Marketing Association in May. The Court held: “Because the beef checkoff funds the government’s own speech, it is not susceptible to a First Amendment compelled-subsidy challenge.”

Because both sides agree that the U.S. Supreme Court ruling is the controlling law in this case, they settled the box-tax litigation by way of a stipulation in the Second District Court of Appeals and a final judgment in favor of the department in the trial court.

Karen McEver is the editor of the Florida Citrus Reporter, (863) 294-3838. E-mail is