Seed pathway for tree pest dissemination: gathering knowledge to improve forest health management

The Earth is not only a blue planet, but also a green one, with forests covering around 38% of habitable
land surface. However, like any other crops, forest health is threatened by pests whose impact varies
greatly depending on the tree species, management practices, and regions of the world. In a context of
global trade, the transport of infested plant materials is a major factor in the spread of organisms to new
territories, which can be the source of emerging diseases. It is critical to deploy strategies to limit this
from happening. All around the world, regional plant protection organizations play key roles to promote
phytosanitary measures. Identifying pests and their vectors is a first step towards risk analysis, and
international initiatives are bringing together research results on the role of seeds as vectors of pests.
The International Seed Testing Association (ISTA) has a long history in promoting uniformity in seed
quality evaluation, as illustrated by the activities of its technical committees on forest tree and shrub seed
(FTS), and seed health (SHC). Among these, ISTA contributes to increase our knowledge of the
diversity of seed pests and to develop suitable detection methods. One of such a tool, the ISTA
Reference Pest List (ISTA-RPL) is a repertoire of seed-borne pathogenic organisms in about 70 plant
species, including a dozen of forest trees. Its aim is to inventory, based on scientific results, if these
pests can (or cannot) be transmitted vertically or transferred in the environment under natural conditions,
making seeds a vector of dissemination. This literature resource may be a valuable source for risk
assessors and policymakers in their goal to evaluate the need to regulate pests or not. It also opens
avenues of R&D work by seed companies, academic laboratories, or industry to develop diagnostics,
detection methods, or treatments.