Is seed a pest risk?
A pest risk analysis (PRA) is the foundation for fact-based and proportionate phytosanitary regulations instituted by a country. However, in practice PRAs are difficult to do. Many countries do not have the resources to perform all the PRAs needed - neither in a reasonable period of time nor with the thoroughness they require. Often they are not specific to seed for sowing. PRAs for seed for sowing must take into consideration that some pests may not be transmitted from the seed to the plant grown from that seed.
The rationale for phytosanitary measures
The three stage process of a pest risk analysis (ISPM 2 and ISPM 11) provides a basis for determining the potential of seed being a pest risk.
1. Identification of an organism and pathway
Even though certain pests may be associated with a given species of plant, far fewer are actually directly associated with the seed of the species in question.
The PRA should determine if the seed is a pathway for the introduction and spread of regulated pests and may lead to establishment of regulated pests in the PRA area.
2. Pest risk assessment, i.e. assessment of introduction, establishment and spread, and assessment of economic impacts
Numerous research papers on plant diseases are published every year. Many note that the pest in question “can or has been found on seeds”. How relevant are such reports?
The presence of a pest on or in the seed does not necessarily mean that it can be transmitted from the seed into the resulting plant.
3. Pest risk management, i.e. identification of phytosanitary measures that (alone or in combination) reduce the risk to an acceptable level
The seed business today uses many recognized risk reduction and prevention measures for seed pests of concern, such as seed certification schemes, resistant varieties, seed testing and seed treatments.