326 G. McCOLLUM AND E. BALDWIN
confirmed present in 31 Florida counties, making eradication of the pest
impossible.
Control of ACP is complicated by the number of orchards that are
not sprayed (both managed and abandoned) along with residential cit-
rus trees which serve as reservoirs for ACP. ACP reportedly arrived in
Texas in 2001 (French et al. 2001) on pottedMurrayaplants that orig-
inated from Florida and are now widely distributed throughout south-
ern Texas in commercial citrus as well as in residential plantings. ACP
were first found in California in 2008, in San Diego County (CDFA press
release, August 29, 2013). The number of ACP finds increased rapidly
in California and the insect has now been confirmed in commercial cit-
rus production regions of the state and 14 counties or parts of counties
have been quarantined based on the presence of ACP (CDFA 2015b).
- CLas, the Presumed Causal Agent of HLB. In 2004, CLas was con-
firmed present in Sao Palo State (Coletta-Filho et al. 2004), the largest
citrus production region in Brazil. This was the first confirmation of
CLas in the Western Hemisphere. In 2005, samples were collected from
a pummelo tree with HLB-like symptoms growing in Southeast Florida,
and infection with CLas was confirmed based on polymerase chain reac-
tion (PCR) cycle number (CN) results (Li et al. 2006b). The origin of CLas
in Florida is unknown; it may have been via infected budwood smug-
gled into the state or via infected ACP.
Curiously, in 2005 when CLas was confirmed in Florida, it was on
the United States Department of Homeland Security select agent list
as it was considered a potential biological weapon of mass destruction.
Because of its select agent status, only individuals who had received FBI
security clearance were allowed to conduct research with CLas. In addi-
tion, CLas/HLB research could only be conducted in greenhouses that
met stringent security restrictions. This select agent status resulted in
a significant impediment to conducting research on HLB in the United
States (Spann 2009). In 2008, CLas was removed from the select agent
list (Federal Register 2008), thereby lifting a significant impediment to
HLB research.
Following the initial confirmation of CLas in Florida, an extensive
survey strategy was implemented to delimit the extent of infections
(Gottwald 2010). Although the initial confirmation of CLas in Florida
was not in an area of concentrated citrus production, the bacterium
was soon found in a commercial citrus orchard approximately 125 km
from the initial find. Gottwald et al. (2007) speculated that this infec-
tion could have resulted from long range dispersal of infected psyllids
rather than by introduction of infected citrus budwood. As surveys for