The invasive weed yellow nutsedge creates considerable problems for Swiss producers in arable and vegetable crops. In a four-year project, stakeholders from research and practice evaluated various control strategies on-farm.
Yellow Nutsedge reproduces and spreads primarily by underground tubers, and can lead to substantial yield losses in arable and vegetable crops. The invasive weed has a very high multiplication potential, and has spread widely throughout certain regions in Switzerland since the 1990s.
Developing and implementing effective control methods
There is no single measure or easily implemented method for controlling yellow nutsedge. Developing and implementing successful control strategies for infested fields is therefore a matter of urgent necessity. The most promising approach is a combination of different, coordinated measures. Great attention must also be paid to the unintentional spread of yellow nutsedge. In order to keep uninfested fields nutsedge-free, agricultural contractors must be informed of the presence of the weed, and all machines must be cleaned after use on an infested field. In addition, nationwide reporting and mapping would make an important contribution to the systematic nationwide control of yellow nutsedge in Switzerland.
Project for evaluating control strategies
In a four-year project, the Federal Office for Agriculture, Agridea, sectoral and producer organisations, cantonal agencies, the Swiss Farmers’ Union and Agroscope combined forces and evaluated the situation. Using a ‘co-creation’ approach, different control strategies were compared and the tuber development in the soil was monitored on 21 infested sites in six cantons. The control measures used were chosen jointly by the farmers and the cantonal extension services, then implemented under the personal responsibility of the farmers. Agroscope monitored yellow nutsedge infestation. For each site examined, the following was recorded: crop grown, herbicides applied and type of soil cultivation.
Crop rotation, soil cultivation and herbicides combat yellow nutsedge
Maize cultivation with the right accompanying measures is best suited for yellow nutsedge control. On the farms successful in controlling yellow nutsedge, maize was generally sown late (up to mid-June), after repeated soil cultivation of the entire field and treatment with Dual Gold (S-Metolachlor). In addition, herbicides were applied post-emergence. Repeated soil cultivation before the sowing of maize, at the 2-to-5-leaf stage of yellow nutsedge, damages the young nutsedge plants or moves them to the surface, where they dry out. This is a highly effective approach, preventing the formation of new tubers.
In some cases wheat cultivation led to a significant decrease in tuber numbers, whilst in other cases the infestation remained constant. Provided that intensive use is possible, sown grassland can reduce or even suppress this weed. Glyphosate only has a good effect on young nutsedge plants (up to the 3-leaf stage). Application therefore only makes sense in the case of small spots of infestation.
- It is very difficult to eradicate infestations of yellow nutsedge, but with suitable methods, tuber density in the soil can be significantly reduced (by more than 90%).
- With low infestation levels or first-time infestations, there are good chances of eradication.
- Yellow nutsedge can be most effectively managed in maize.
- Successful control is always a long-term process over several years, requiring the combination and professional execution of different methods.
- Nationwide reporting and mapping could play an important role in preventing the further spread of yellow nutsedge in Switzerland.
- Regular consultations for farmers are essential, since controlling yellow nutsedge is a very complex, time-consuming and expensive undertaking.
- It is important to get the message across that farmers are not powerless against yellow nutsedge, even if there is no one single effective control method.