Contributions of Pollen and Seed to Impurity in Crops – A Comparison of Maize, Oilseed Rape and Beet

How can flexibility be integrated into coexistence regulations? A review

“…loss in value, analytical costs to ensure compliance with labelling and traceability requirements and for liability claims) to farmers who grow non‐GM crops due to on‐farm mixing of agricultural products. Various sources can contribute to on‐farm mixing of agricultural products, including: (i) the use of impure seed; (ii) cross‐fertilization due to pollen flow between neighbouring fields; (iii) the occurrence of volunteer plants originating from seeds and/or vegetative plant parts from previous GM crops; (iv) mixing of plant material in machinery during sowing, harvesting and post‐harvest operations; and (v) to a much lesser extent, cross‐fertilization from feral plants . Owing to these various sources, completely avoiding the unintentional presence of GM material in organic and conventional (non‐GM) crop products can be challenging.…”

“…Cross‐fertilization due to pollen flow between neighbouring fields represents the major potential biological source of on‐farm mixing in maize: maize is a cross‐pollinated crop, relying on wind for the dispersal of its pollen; there are no cross‐compatible wild relatives of maize in Europe; maize plants are only winter hardy in European regions with mild winters, and in those situations maize kernels remaining in the field after harvest can germinate, grow, flower and locally cross‐pollinate neighbouring maize plants; yet these plants grow weakly and tend to flower asynchronously with the cultivated maize crops in which they occur; and maize is not able to survive as feral populations outside cropped areas due to its high degree of domestication. Although different preventive on‐farm measures could be implemented to reduce cross‐fertilization in maize, several EU member states are currently proposing isolation distances as the main coexistence measure to comply with legal tolerance threshold requirements .…”

“…Approximately 95–99% of the released pollen is deposited within about 50 m from the source. Very low levels of cross‐pollination can occur over distances up to kilometres under suitable climatic conditions, but most cross‐pollination events occur within 40 m of the pollen source …”

“…Flexibility could be integrated by allowing diversified coexistence measures that are not only negotiable between farmers on a case‐by‐case basis, but that are also adaptable to different regional and local situations. An inflexible approach that requires, for instance, setting a standard isolation distance or pollen barrier is unnecessary in many circumstances . One caveat here is that policy makers and regulators are reluctant to adopt such a case‐by‐case coexistence approach because of the difficulties of implementation.…”

A simulation model to evaluate the effect of cooperation between grain merchants in managing GM and non-GM segregation for maize

“…This can be done in two ways. The first is to have an isolation distance between GM and non-GM fields (Byrne & Fromherz, 2003;Squire, Lecomte, Hüsken, Soukup, & Mess ean, 2013) because maize pollen has a short dispersal range (Della Porta et al, 2008). The second is to ensure a time lag between the growth of GM and non-GM crops so that they do not flower simultaneously (Messan et al, 2006, 112 pp.…”