Overview
Trade is restricted to specific stages of development or harvest maturity where the risk of infestation is low.
- Examples include restricting trade to fruit developmental stages that are less vulnerable to infestation (e.g.. immature stages), and limiting imports of plant material for planting to tissue culture or seed.
- Evaluating the efficacy of this measure requires evidence that restricting trade to a less vulnerable developmental stage will reduce risk to an acceptable level.
- The vulnerability of the developmental stage intended for export is typically considered when conducting a pest risk assessment. Restrictions on the developmental stage that can be traded can also be applied as a phytosanitary measure.
- For assurance, the maturity of the exported commodity can be assessed as part of a pre-border consignment inspection by authorised personnel, with oversight by the NPPO or relevant authority of the exporting jurisdiction.
Evidence to support efficacy
The vulnerability to pest infestation will often differ with developmental stage of a commodity. A particular developmental stage can be on a continuum from being a non-host (referred to as a conditional non-host in RSPM 4) through to a good host.
Scientific evidence needs to demonstrate that a clearly identifiable (and gradable) stage of the commodity is sufficiently less vulnerable to infestation, relative to alternative stages, when exposed to the pest under the same conditions. Considerations and experimental methods are similar to those applied in host or carrier studies.
Applying the measure
How it is used
This measure applies to commodities where developmental stage is relevant, and where there can be scope to restrict trade to specific developmental stages. This includes plants for planting, and some fruit and vegetables. For many pests, early developmental stages of the fruit are less vulnerable to infestation, or may even be non-hosts (conditional on developmental stage).
The developmental stage of the export grade commodity is identified and defined at the scoping stage of an import risk assessment, and informs the estimation of unrestricted risk in a pest risk assessment. If a commodity is only traded commercially at developmental stages that are considered non-hosts (conditional non-hosts, as defined in RSPM 4), additional measures may not be necessary. Alternatively, trade can be limited to specific developmental stages that are a conditional non-host for the target pest.
Where practical, the movement of plants for planting can be restricted to developmental stages that are least vulnerable to being infested. For instance, different plant stages such as seeds, tissue culture, young plants and mature plants may have different risk profiles. Limiting trade to the tissue culture pathway may exclude fungal and most bacterial pests.
Trade in climacteric fruit that continue to mature after harvest may be restricted to less mature stages that are less vulnerable or that may even be conditional non-hosts.
Use with other measures
Conditional non-hosts require no other phytosanitary measures while they remain in the non-host condition (RSPM 04).
A developmental stage requirement is often combined with a quality specification. For example, fruit may need to be of a certain developmental stage, and not have any external damage. It can also be combined with the host or carrier measure, with trade being restricted to the least vulnerable developmental stage of an already poor host.
Poor developmental stage can be combined with other measures within a phytosanitary systems approach, such as a Low Pest Prevalence Site measure.
Similar measures
Developmental stage is closely related to, and sometimes considered as a component of, the host or carrier measure. It is also functionally similar to quality specifications.
Assurance of correct implementation
There may be requirements for training and standard operating procedures to ensure that the commodity is harvested and/or graded at the specified developmental stage. Compliance with any maturity requirements may be assessed as part of a pre-border consignment inspection by authorised personnel, with oversight by the NPPO or relevant authority of the exporting jurisdiction.
References
The Asia and Pacific Plant Protection Commission (APPPC), 2005. Regional Standards for Phytosanitary Measures (RSPM) 04. Guidelines for the confirmation of non-host status of fruit and vegetables to tephritid fruit flies. Food and Agriculture Organization of the United Nations Regional Office for Asia and the Pacific, Bangkok, Thailand.