Ambrosia artemisiifolia L. seeds in bird feed in southern Belgium, 10 years after the EU regulation

Description of the subject. Common Ragweed (Ambrosia artemisiifolia L.) is a problematic invasive plant which population has recently spread/increased throughout Belgium. Previous studies in European countries have pointed out wild bird and poultry feed trade as a vector of introduction. In 2011, a maximum limit of contamination was imposed by the European commission. Objectives. The goal is to quantify the level of bird seed contamination sold in Southern Belgium. Method. In 2021, we analyzed 42 bags of bird feed, purchased in various retailers in Southern Belgium. We distinguished wild bird seed mixes, poultry seed mixes and sunflower seeds. Results. Regardless of the moisture of the samples (not measured), the results of the samples were not near the legal limit. However, 13 out of 42 samples contained common ragweed seeds and 0.75 ± 0.265 seeds (mean ± standard error) per kilo of bird feed were found on average, of which 82.4% were viable. Conclusions. Although the legal limit seems to be respected, the bird feed trade still represents a substantial introduction pathway for ragweed.