- HUANGLONGBING: DEVASTATING DISEASE OF CITRUS 337
great risk of becoming HLB-infected early on, and never developing into
a productive tree (Hall et al. 2014). Finally, to successfully establish new
orchards, it is imperative to keep them free of ACP for as long as possible
to prevent infection, the younger a tree is when it becomes infected, the
shorter its life will be, and if infected young enough, the trees will never
become productive.
B. Identify and Remove Infected Trees
Scouting orchards to identify trees with apparent HLB symptoms and
then removal of those trees is a component of the three-pronged manage-
ment strategy. Unfortunately, by the time HLB symptoms appear, CLas
has reached high titer (McCollum et al. 2014), and the tree has been serv-
ing as a source of inoculum for months if not years. Numbers of infected,
but asymptomatic trees always outnumber symptomatic trees early in
the development of an epidemic, whether on an orchard, local, regional,
national, or worldwide scale. The longer the delay between confirma-
tion of infection and tree removal, the greater the chance for the spread
of CLas. However, no inspections are able to detect all symptomatic
trees present in an orchard. In addition, ACP can acquire CLas from trees
that are infected, but asymptomatic (Coletta-Filho et al. 2014). Irey et al.
(2006) estimated that for every HLB-symptomatic tree in an orchard
there are at least twice as many trees that are infected with CLas, but
not yet visually symptomatic.
Although the systematic identification of and elimination of CLas
infected trees is the most effective and recommended method of dis-
ease management, it is also the least acceptable to citrus growers who
perceive this method as not economically sustainable. Elimination of
recently affected HLB trees represents an immediate 100% loss of yield
for the tree, and cost increase due to the need of frequent inspections
and removal operations. Furthermore, although tree removal can slow
the spread of HLB in large plantings, tree removal in small plantings is
not effective (Bassanezi et al. 2013).
C. Clean Nursery Stock
It is essential to produce nursery trees that are free of CLas (as well
as other graft-transmissible pathogens). In Florida, the Florida Division
of Agriculture and Consumer Services (FDACS), Department of Plant
Industry (DPI), Bureau of Budwood Protection have responsibility for
all certified nursery stock. All commercial citrus nursery stock produc-
tion starts with certified budwood that originates with DPI. Stringent