Overview
Approved imports are limited to times of the year when conditions are unfavourable for pest establishment.
- Examples include restricting imports to certain seasons, or, alternatively, other import requirements may be reduced or removed during those low-risk periods.
- Evaluating the efficacy of this measure requires knowledge of the biology of the pest in relation to the seasonal conditions in the importing area, including the seasonal availability of alternative hosts.
- Seasonality can be considered during pest risk assessment. This may be particularly relevant where export and import jurisdictions are counter-seasonal. When applied as a measure it most commonly results in the seasonal application of other measures.
- Assurance can be achieved by issuing import permits for approved times of year, and audit of the timing of imports and post-border supply chain movement, if appropriate.
Evidence to support efficacy
Evidence is needed to demonstrate that the seasonal climate conditions are sufficiently unsuitable in the importing area to justify the import and/or movement restrictions. Similar to poor destination habitat, important considerations include the climatic conditions needed for establishment, which can be informed by bioclimatic modelling, host availability, the presence of vectors, and existing pest management practices. For some pests (e.g. with environmental cues for diapause release) the effect on establishment risk of moving between hemispheres may need to be considered.
Applying the measure
How it is used
The seasonality of imports may be considered during a pest risk assessment when considering the likelihood of establishment and spread. This is particularly relevant for pests on commodities that cross hemispheres and may be exposed to counter-seasonal conditions that reduce establishment risks. Risk assessment may also seasonally guide the intensity of at the border inspections undertaken by the importing jurisdiction.
Seasonality can be applied as a phytosanitary measure to take advantage of seasons when establishment likelihood is low. For example, when introduced pest life stages do not have strategies to survive until the correct environmental cues for diapause release occur, or until hosts become seasonally available.
Use with other measures
This measure can be considered together with poor destination habitat, further reducing the likelihood of establishment.
Year-round imports may still be permitted when seasonal import restrictions are applied as a measure. However, additional or strengthened measures will be required during those seasons that are more favourable for the entry and establishment of the pest. For example, the requirement for pre-border inspections of ships or sea containers could be increased.
Similar measures
The time of year when imports are permitted can be restricted by two measures that reduce risk in different ways. Seasonality of imports limits imports to when conditions for establishment are unfavourable in the importing jurisdiction. Limit seasonal overlap only allows exports to occur when the risk of exposure to the pest in the exporting jurisdiction is low (e.g. fruit that is harvested during a “winter window” when pests are not active). Both may be relevant if trade occurs when both infestation and establishment risks are low in their respective jurisdictions.
Assurance of correct implementation
For assurance, import permits may only be endorsed during those times of the year that are unfavourable for the pest in the importing jurisdiction. Audit of the timing of imports to ensure compliance with any seasonal window requirements may be required.