EPPO Global Database

EPPO Reporting Service no. 10 - 2021 Num. article: 2021/232

Weed seed contamination in seed shipments to New Zealand

EPPO Pest Risk Analyses on invasive alien plants highlight the import of seed as important pathways for the introduction of invasive alien plants (e.g. Amaranthus palmeri, A. tuberculatus and Ambrosia trifida). Effective management of this pathway is a significant means of reducing future plant introductions and can help to minimise agricultural losses. The current study examined a national border inspection database that contained data on the frequency, origin and identity of contaminant seeds within seed for sowing shipments entering New Zealand between 2014–2018. The study assessed 41 610 seed lots across 1 420 crop seed species from over 90 countries. Overall, contamination was rare, occurring in only 1.9% of all seed lots. Among the different crop types, arable seeds had the lowest average percentage of seed lots contaminated (0.5%) compared to forage seeds which had the highest average level of contamination (12.6%). Crop seeds CapsicumPhaseolus and Solanum had the lowest contamination rates (0.0%) whereas forage crops Medicago (27.3%) and Trifolium (19.8%) had the highest contamination rates. Out of 191 genera recorded as contaminants, Chenopodium was the most common. Regulated quarantine weeds were the rarest contaminant type, only occurring in 0.06% of seed lots. Sorghum halepense was the most common quarantine species and was only found in vegetable seed lots. Vegetable crop seed lots accounted for approximately half of all quarantine species detections, Raphanus sativus being the most contaminated vegetable crop (by quarantine species). Larger seed lots were more contaminated and more likely to contain a quarantine species than smaller seed lots.


Rubenstein JM, Hulme PE, Buddenhagen CE, Rolston MP, Hampton JG (2021) Weed seed contamination in imported seed lots entering New Zealand. PLoS ONE 16(8), e0256623. https://doi.org/10.1371/journal.pone.0256623