HLB control

The University of Florida estimates that in the State, HLB has resulted in the loss of more than 6,600 jobs, $1,3billion in revenue to growers and $3,6 billion in economic activity. Can HLB be controlled, how and when? Answering these questions is the goal of the workshop! Two forms of HLB have to be considered: (i) hightemperature-sensitive African-HLB, with Candidatus (Ca.) Liberibacter (L.) africanus and the African CitrusPsyllid, Trioza erytreae, and (ii) high temperature-tolerant Asian-HLB, with Ca. L. asiaticus and the Asian CitrusPsyllid, Diaphorina citri (2). African-HLB is presumed to be less aggressive than Asian-HLB. There is little or no evidence of genetic resistance to HLB in citrus. Apparently, citrus has had only a recentassociation with Liberibacter species, an association too short to have built up resistance to the bacterium. Hence, according to a general consensus, resistance to HLB will probably be obtained by engineering, intocitrus, genes with anti-Liberibacter and/or anti-psyllid activity (8). However, such HLB-resistant cultivars willprobably not become available to the growers for several years and, in the meantime, solutions must bedeveloped to control HLB and save the existing citrus industry from destruction (1, 3, 9). Thus, for HLB control,short-term systems for “today” and long-term systems for “tomorrow” must be discussed. Short-term systems. Even though they are called “short-term”, these systems, when efficient, will probablyhave to be used for several years. Various systems are known and listed. (i) The classic, Three-ProngedPackage (TPP) has been recommended in China since the 1950s and is comprised by (a) insecticide treatmentsagainst psyllids, (b) detection and removal of symptomatic trees, and (c) resets with disease-free trees frominsect-proof nurseries. TPP is a “preventive” control system; as it “prevents” trees from becoming infected. Application of the TPP in S?o Paulo State, Brazil, since 2004 when HLB was first iden