336 G. McCOLLUM AND E. BALDWIN
IV. MANAGEMENT STRATEGIES TO MINIMIZE OR PREVENT
HLB DISEASE
In areas where ACP, and as a consequence, HLB have not been found,
exclusion of ACP is the best defense against the disease (Bove 2006). ́
However, once HLB is present and especially if widespread as was the
case in Florida, there is no way to eradicate ACP and CLas inoculum.
From that time forward, only HLB management can be considered.
The following three-pronged approach to combat HLB was developed
in the 1980s (Aubert 1990) under the auspices of the United Nations
Development Program, Food and Agriculture Organization Southeast-
ern Asian citrus rehabilitation project.
A. Control the ACP Vector
As soon as ACP is found, it is essential to begin rigorous control. In
Florida, applications of insecticides targeting ACP did not begin until
HLB had been confirmed, 7 years after ACP were first confirmed in the
state. By the time it was confirmed that CLas was present in Florida,
ACP had reached high populations throughout the state. This was the
first mistake resulting in the current Florida citrus industry’s dire sit-
uation. The number of insecticide treatments on Florida citrus has
increased from three to four per year, to more than 12 using combi-
nations of systemic and contact materials (Spreen et al. 2014). Area
wide programs, known in Florida as Citrus Health Management Areas
(CHMAs) for coordinated application of insecticides over large areas, is
the most effective way to reduce ACP populations, and may slow spread
of HLB, but will not cure trees. Some growers question the need to con-
tinue to apply insecticides when an orchard becomes widely infected
with CLas. Hall et al. (2014) reported that up to eight monthly pesticide
treatments per year applied on a calendar schedule were ineffective for
preventing young citrus from becoming HLB symptomatic when sur-
rounded by high levels of CLas+ACP. Recent studies in Brazil and
Florida have concluded that area-wide insect control, over large areas
consisting of thousands of hectares, can reduce vector populations to
the point where HLB can be managed (Gottwald 2010; Bassanezi et al.
2011). There is some evidence (Stansly et al. 2014) that suggests contin-
ued insecticide treatment of CLas-infected trees reduces the chance for
additional infections and thereby slows the rate of tree decline.
Even in the absence of HLB, there is attrition of trees in citrus orchards
(ca. 5% per year in Florida) and these trees have to be replaced with
nursery trees for orchards to sustain productivity. Young trees are at