Potted plants as pathway for introducing invasive alien plants
Although potted plants are a well-known pathway for introducing weeds in general (see Q-bank interactive key), and often mentioned as a potential pathway in EPPO PRAs for invasive plant species (e.g. Polygonum perfoliatum (Polygonaceae) and Microstegium vimineum (Poaceae); both EPPO A2 pests) actual proof is generally missing to support such an assertion. However, recently a number of invasive alien plants have been intercepted by the Dutch NPPO as a contaminant of potted plants. In a targeted survey for contaminants in potted plants from South America, Parthenium hysterophorus (EPPO A2 pest) was discovered in an import of Coffea arabica (Rubiaceae) from Honduras. In another example, in August 2015, a single contaminated Chaenomeles (Rosaceae) potted plant (from a consignment from China) was sent to the NPPO for identification. The consignment had already been inspected in the summer of 2014 however, the inspector noted the presence of a thorny weed within the pot but no report or action was taken. In 2015, following a routine inspection on planting at an import/export production facility, P. perfoliatum was identified from the consignment of Chaenomeles which had remained outdoors the previous winter. Following a simple Google search the inspector was directed to the EPPO website and was able to correctly identify the species as P. perfoliatum. The clear warning at the EPPO website resulted in the owner being requested to destroy all infested potted plants and to send one infested plant to the Dutch NPPO for verification purposes. Discussions between inspectors about the interception of P. perfoliatum resulted in the same species being identified as a contaminant of a shipment of Ficus microcarpa (Moraceae) from China. As a follow up action a survey of the import facility where the shipment of Chaenomeles had been outdoors was performed but no other plants of this easily recognisable species were found.
Sources
Personal Communication: J. van Valkenburg, Q bank http://www.q-bank.eu/
Q bank interactive key: