NJF/EWRS Workshop on recent advances in IWM of perennial and annual weeds, with special emphasis on the role of crop-weed interactions

Time: 27-29 January, 2014
Place: Uppsala, Sweden

This workshop was organised as a collaboration between the NJF working group “Perennial weeds” and the EWRS working group “Crop-Weed Interactions” and was held at the Ecology Centre at the SLU Campus in Uppsala, Sweden from 27-29 January 2014. The workshop was attended by 23 participants from 12 countries. The 20 presentations were arranged in five sessions and gave rise to interesting discussions. On Monday and Tuesday, the conversations were continued during joint dinners organised at the Ecology Centre and at Sunnersta Herrgård, the location where most foreign participants stayed overnight. The local arrangements made by SLU staff and students are gratefully acknowledged.

The first session, on perennial weeds, focused on the factors influencing growth and control of the most common perennial weed species in the Nordic-Baltic countries. Integrated control measures were addressed in terms of crop-weed competition, mechanical control methods and timing of treatments. New interesting results related to the compensation point of perennial species (the time when the energy resources in underground regenerative structures are at minimum level) were presented.

The second session focused on cultural control. In winter wheat, crop density, time of sowing and cultivar were identified as important factors, whereas spatial distribution did not seem to be of importance. The methodology for identifying crop traits responsible for competitiveness against weeds was discussed and the various aspects related to seed vigour were presented. The first results of a long-term experiment studying the influence of crop rotation in maize-based cropping systems were also presented. This session continued on Tuesday, when it dealt with the importance of synergism among cultural weed control measures and the competitive ability of cereal cultivars. Future research should identify where in the life cycle of weeds cultural control measures can reinforce one another to reduce the size of the weed population most efficiently. The suppressive ability of cereal varieties is an important component in this context, as it reduces the impact of weeds on crop yield, including the weed seed return to the seed bank. Ongoing research in the UK is adding more understanding about the attributes of varieties that play a major role in the suppressive ability of varieties.

In the third session, the attention was on competition and growth. Investigations on a range of different crop-weed combinations were presented. The more traditional arable cropping system was represented by large-scale field trials on the competition between wild oats and spring wheat and comparison of the competitive ability of different spring barley varieties. Perennial weeds in grasslands were represented by a study on the competitive effect and spread of soft rush and compact rush (Juncus spp.) in extensive pastures and more intensively managed leys along the western coastline of Norway. The focus was on the influence of soil moisture and organic matter on the competitive ratio between Juncus spp. and Poa pratensis. A further two presentations discussed the role of crop-weed competition during the establishment phase of Salix genotypes (willow). In a first presentation the commonly practised winter storage of willow cuttings was questioned. Establishment of willow stands derived from stored cuttings was compared with that of stands based on fresh cuttings under both weed-free and weedy conditions. In another presentation the weed-free period of willow plantings was discussed. In that study white mustard and spring barley were used as model weeds, resulting in a discussion on ‘how to select your ideal model weed’.

In the fourth session, different aspects of direct weed control measures were discussed. In Finland, tillage practices have changed. Stubble cultivation and direct drilling have become more common, which is influencing the composition of the weed flora. In Norway, the effects of different timings of soil cultivation on perennial weeds are being studied and interesting results were presented. A study on combinations of mechanical and chemical weed control in oilseed rape performed in Sweden was presented and it was shown that such combinations can be successfully implemented to further develop integrated weed management (IWM) strategies.

The last session was on IWM, an issue that in fact had already been an important topic throughout the workshop. In an informative and interesting talk on ‘Challenges for Integrated Weed Management implementation in EU crops’, the consequences of the new EU policy were illustrated. This was followed by a fruitful discussion on the role of GM crops and the opportunities and problems with implementing IWM in Europe. After this final session, the local organisers were thanked once more for facilitating the workshop and for their major role in making this workshop such a success.

Organising committee

  • Lammert Bastiaans, Wageningen University, The Netherlands
  • Lars Olav Brandsæter, Bioforsk, Norway
  • Anneli Lundkvist, Swedish University of Agricultural Sciences, Sweden
  • Bo Melander, Aarhus University, Denmark
  • Jukka Salonen, MTT Agrifood Research Finland, Finland
  • Theo Verwijst, Swedish University of Agricultural Sciences, Sweden