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G. J. Hallman
literature to describe host status; terms such as “rarely infested” are not helpful
in defining host range.
21.3.1.2 Systems Approach
A systems approach to achieving quarantine security is “[t]he integration of
different pest risk management measures, at least two of which act independently,
and which cumulatively achieve the appropriate level of phytosanitary
protection” (FAO 2004). Pest risk management measures are available options
to reduce the risk of introduction of a pest, and may be applied at appropriate
times when they will have an effect in reducing pest risk at any point from
before a commodity is planted to before it arrives at market (Table 21.1).
These measures usually form part of an official protocol that must be followed,
and achieve a specific goal, such as maintain pest trapping numbers
below a predetermined level. If that level is exceeded, then export may be
halted until corrective measures restore risk to acceptable levels. Jang and
Moffitt (1994) present a thorough discussion of the systems approach.
Pre-plant or pre-season measures include those that define the pest prevalence
in the area through trapping and sampling, host suitability, and the pest
population level when susceptible stages of the host part to be exported are
present. Off-season pest mitigation measures often must be carried out even
though the commodity in its exported stage is not present. The use of attractants
to detect and suppress pests is discussed by Robacker and Landolt
(2002).
During the growing stages when the exportable part of the commodity is
present in the fields, attention is focused directly on preventing infestation of
the commodity. Survey trapping may be increased, and toxic baits may be
employed to keep population levels from exceeding the limit of tolerance.
Field applications of pesticides may be employed.
After harvest, the only methods for reducing pest infestation levels are
culling of infested commodities, or a disinfestation treatment. If a disinfestation
treatment is used as part of a systems approach to phytosanitary security,
theoretically the treatment would not need to achieve the same level of control
as a stand-alone phytosanitary treatment. Cowley et al. (1991) developed
a methyl bromide fumigation treatment for watermelons that depended on
the poor host status of watermelons, fruit fly control in the field, and culling
of damaged, softened or misshapen fruit to reduce infestation levels of the
fruit fly Bactrocera xanthodes to levels that would be controlled by a lower
than usual dose of methyl bromide. For this scheme to be a true systems
approach, each of the steps in the system would be precisely defined in the
protocol.
Although systems approaches avoid the expense of treatment, they require
a continual expense of the pest risk management measures required to keep