The experience of Huanglongbing control in Brazil

Symptoms of Huanglongbing (HLB) were first reported in S?o Paulo State (SPS) near Araraquara in 2004. However, the insect vector, the Asian citrus psyllid, Diaphorina citri, has been present in SPS since 1940 andis responsible for the spread of HLB to most regions of SPS. Immediately after HLB was identified in March 2004, Fundecitrus recommended HLB-management in allthe citrus farms of SPS as an attempt to control the disease and save the industry from destruction. Themanagement involved three classic measures: (i) insecticide sprays of all trees, several times a year, to decreasethe insect-vector population, (ii) identification and immediate removal of symptomatic trees, several times ayear, to rid orchards of sources of inoculum, and (iii) replacement of removed trees by young, HLB-free treesfrom covered, insect-proof nurseries. HLB-management by this “three-pronged system” (TPS) was evaluatedby determining the total number of symptomatic trees removed each year in the various blocks. Indeed,successful management would result in decrease of the total number of symptomatic trees removed per year,while unsuccessful management would lead to an increase of such trees. Since 2004, crucial factors having a strong influence on HLB-management by the TPS have been identified. 1) HLB incidence in the region where the farm is located and 2) HLB incidence in the farm. For instance,when HLB is first detected in a region or country where the psyllid vector has been present for some time(Brazil in 2004, Florida in 2005, Texas and California in 2012) the incidence of the disease is generally low. HLB management by the TPS is easier when the HLB incidence at onset of the management is low (≤ 7%). 3) When a farm with good HLB management is close to a farm with no or poor management, HLB-controlin the “good” farm becomes much more difficult because the highly infected psyllids from the “poor” farminvade and contaminate the “good” farm. In this case, more aggressive psyllid co