EWRS Working Group:

European Weed Mapping

Objectives

The objectives of the EWRS Weed Mapping WG is: i) to provide an overview on the occurrence and spreading of weeds in Europe and other continents and ii) to exchange data, tools and methods for the assessment, tempo spatial documentation of species and biotypes on field crops, orchards and non-crop land (natural / urban / historical landscape).

The WG implements its mission through the following tasks:

  • to compare and combine data from weed surveys in physical maps,
  • to document population dynamics and regional weed changes,
  • to derive predictions for weed problems in selected areas and on selected sites,
  • to communicate developments in defined segments and compare them with developments outside the EU and
  • to find common and most efficient rules and tools for the assessment and documentation of data.

Certain Principles are taken into account such as:

  • Sampling procedures in weed surveys require careful methological approach
  • Ranking of weeds based on Weed Abundance and continuous mapping gives us the opportunity to provide long term predictions about weed population changes on a field and regional levels.
  • Weed densities should be clustered according to Braun-Blanquet
  • Cover is one of the most common measures of community composition because it equalizes the low contribution of species but abundant, and the species of high growth but of low density
  • The correlation of weeds occurrence with environmental or agronomic factors is a useful tool to explain and to predict the global distribution of weeds
  • Resistant weeds, invasive plants and rare weeds can be documented with maps contributing to biodiversity
  • Previous surveys should be taken into account .
  • The best times for mapping weeds are before weed control applications (pre and post) and before harvest
  • Every species/biotype should be documented separately
  • The most evident way to demonstrate weed densities appears to be a colored depiction where a dark color represents high densities and light color low densities