HUANGLONGBING-CONTROL WORKSHOP: SUMMARY

The present work is a summary of all contributions (listed below) performed during the HLB-control workshop held during the 12th International Citrus Congress in Valencia, Spain.
The University of Florida has estimated in 2012 that, in Florida, Huanglongbing (HLB) has resulted in the loss of 6,611 jobs from 2006 throughout 2011, $1,3 billion in revenue to growers and $3,63 billion in economic activity. The State’s commercial citrus acreage has shrunk to 531,493 acres as of the fall of 2012, a 28% decline from 748,555 acres in 2004. For the 2012/2013 season, the USDA has revised the crop forecast downward twice since October, when the outlook was for 154 million 90-pound boxes of oranges, but in January the estimate predicted only a crop of 142 million boxes. The grapefruit forecast has dropped to 18 million boxes from 20.3 million. Also in São Paulo State, Brazil, HLB has taken a heavy toll. Since 2004, 18 million HLB-affected trees (~10%), representing a value of 216 million US$ at 12 US$ a tree, have been eliminated.
Can HLB be controlled, how and when? Answering these questions was the goal of the HLB control workshop! Two forms of HLB were considered: (i) high temperature-sensitive African-HLB, with Candidatus (Ca.) Liberibacter (L.) africanus and the African citrus psyllid vector, Trioza erytreae, and (ii) high temperature-tolerant Asian-HLB, with Ca. L. asiaticus and the Asian citrus psyllid vector, Diaphorina citri (Bové, 2009).
There is little evidence of genetic resistance to HLB in citrus. Apparently, citrus has had only a recent association with liberibacters, an association too short to have built up resistance to the bacterium. Hence, according to a general consensus, resistance to HLB is supposed be obtained by engineering, into citrus, genes with anti-liberibacter and/or anti-psyllid activity (National Research Council, 2010). However, such HLB-resistant cultivars will probably not become available to the growers before several years and, in the meantime, solutions must be developed to control HLB and hopefully save the present day citrus industry from destruction (Belasque Jr et al., 2010; Chamberlain, 2010; Timmer et al., 2011). Thus, for HLB control, short-term systems for “today” and long-term systems for “tomorrow” have been discussed. In addition, for regions or countries at risk of HLB, such as Argentina, California and Texas, contingency plans have to be considered.