Biology Reference
In-Depth Information
“basin wide” sterile Medfly release program was initiated over a 1464-square
mile area; 250,000 sterile flies per square mile per week were released over the
entire area and 250,000 sterile flies were released, as well, in the areas where 73
wild flies were found in 1994; this effort was concluded in March 1996.
In 1996, a “preventative” release program was initiated over a 2155-square
mile area in four counties to “prevent the development of Medfly infestations
and to limit the geographic size of any that manage to start” (CDFA 2002). The
releases involved at least 125,000 sterile Medflies per square mile per week and
an additional 125,000 sterile flies over a high-risk area in central Los Angeles.
No Medflies were found during 1996. During 1997, 24 wild Medflies were found
in Los Angeles County, which led to increased efforts, including ground sprays,
fruit stripping, soil drenches with pesticides under infested trees, and sterile
fly releases that were increased to 500,000 per square mile per week within a
9-square mile area around each infested site.
Between 1975 and 1990, aerial spraying of malathion in baits had been used
to kill the Medfly but, after considerable public concerns were raised about
potential negative environmental and health effects, aerial application of this
pesticide was banned in California. In the early 1990s, agricultural experts and
entomologists hotly debated whether the eradication methods were effec-
tive. One “camp” believed that a combination of releasing millions of sterile
Medflies, plus implementation of effective quarantines, and the use of attrac-
tants and traps to delineate the infestation zone and to monitor the effective-
ness of the SIRM program was effective. Others believed that eradicating the
Medfly from the Los Angeles basin was nearly impossible and that these meth-
ods were failures.
One of the significant questions in the debate is whether the Medfly was
a “permanent resident” of California, especially in the Los Angeles area, or
whether the ongoing outbreaks were the result of additional independent inva-
sions (
Carey 1996a,b, Headrick and Goeden 1996, Myers et al. 2000
,
Figure 13.4
).
This issue was hotly debated and created considerable animosity. Until 1990,
scientists and government officials assumed that each Medfly outbreak origi-
nated from flies that arrived from another country, hitchhiking within agricul-
tural products imported into or smuggled into California. Many believed that
the source of the invasions was from Hawaii. The other group believed, how-
ever, that the Medfly had become permanently established and was being main-
tained at undetectable levels, due in part to the inability of Medfly traps to
detect very low-density populations.
