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Yellow nutsedge (Cyperus esculentus) is a troublesome weed in Switzerland. It reproduces mainly by tubers, but also by seeds. Dormant tubers in the soil cannot be controlled with herbicides. Pigs are known to reduce yellow nutsedge infestation levels by rooting up and consuming tubers. We hypothesized, that old pig breeds would especially be suited for yellow nutsedge control, as they search more actively for feed in the soil than modern pig breeds. A field trial with old pig breeds (Turopolje and Mangalica) was carried out in a field infested with yellow nutsedge (2019-2020). The pigs stayed in the field for 8 months. Infestation levels were determined before and after the trial by counting C. esculentus plants at 50 monitoring sites in the field. In addition, soil samples were taken before and after the experiment. The samples were placed in the greenhouse and emerging yellow nutsedge shoots were considered as a measure of the tuber bank in the soil. After 8 months of pig grazing in the field, we observed significantly less yellow nutsedge plants at the monitoring sites. Yellow nutsedge infestation levels i.e. the tuber bank was significantly reduced by 90%. This reduction is higher than the ones achieved in previous experiments and reported in the literature. Grazing of old pig breeds could be a non-chemical and an appealing approach for the public to considerably reduce yellow nutsedge infestation levels in affected fields.

Erdmandelgras (Cyperus esculentus) stellt ein großes Problem im Schweizer Gemüse- und Ackerbau dar. Mit dem Ziel, stark verseuchte Flächen zu sanieren, wurden an vier Standorten 3-jährige Schwarzbrache Streifenversuche (2018 bis 2020) auf landwirtschaftlichen Betrieben durchgeführt. Dabei wurden vier Versuchsvarianten verglichen: A. Wiederholte Bodenbearbeitung (BB), B. Wiederholte BB + einmalige Einarbeitung von Dual Gold (2 l/ha), C. Wiederholte BB + einmalige Anwendung von Equip Power (1,5 l/ha), D. Wiederholte BB + einmalige Anwendung von Monitor (25 g/ha). Die Landwirte konnten selbst auswählen, welche Geräte sie zur BB verwenden. Zur Bewertung der Wirkung wurden die Knöllchenzahlen pro Liter Erde zu Beginn des Versuchs (Ende 2017), nach einem Jahr Schwarzbrache (Ende 2018) und nach drei Jahren Schwarzbrache (Ende 2020) bestimmt. Nach drei Jahren Schwarzbrache gingen die Knöllchenzahlen auf allen vier Betrieben um durchschnittlich 75 % zurück. Es konnten keine statistisch signifikanten Unterschiede zwischen den Versuchsvarianten nachgewiesen werden, d.h. der Einsatz der Herbizide brachte keinen Zusatznutzen für die Reduzierung der Knöllchenzahl im Boden unter diesen Versuchsbedingungen.

In onions (Allium cepa) few herbicides are registered. Due to their erect leaf and plant structure, onions retain less herbicide after spraying than broadleaved weeds. Further, onion plants have a thicker plant cuticle. These differences allow a selective use of pelargonic acid in onions. The main aim of this study was to determine the selective dose at different crop growth stages. Five field trials were carried out. Three pelargonic acid containing products (1 SL- and 2 EC-formulations) were applied with a logarithmic sprayer. Dose range was 0 to 56 kg active substance (a.s.) ha-1. The growth stage varied between BBCH 10 and 16. Selectivity was rated visually. The products were selective at 7.2 and 8.3 kg a.s. ha-1 (BBCH 10-11), 6.1 and 8.9 kg a.s. ha-1 (BBCH 11-12), 8.5 and 20.7 kg a.s. ha-1 (BBCH 13) and 6.3 and 9.0 kg a.s. ha-1 (BBCH 14-16) for the SL- and EC-products respectively. Selectivity depended on growth stage and weather conditions. Important for selectivity is an intact cuticle, a rain-free, light-intense period before application. Pelargonic acid could become a component for sustainable weed control in onions. Due to its foliar activity, small weeds need to be targeted and several passes are required.

Yellow nutsedge (Cyperus esculentus) is a troublesome weed. It reproduces and spreads mainly via tubers, but also viable seeds are produced. The seeds are very small and have little resources stored. The seedlings are very fragile and look like grasses (poaceae). We hypothesized that C. esculentus plants originating from seeds are more susceptible to herbicides than plants originating from tubers. Cyperus esculentus plants grown from seeds in the greenhouse were treated with glyphosate, bentazone, bromoxynil, pelargonic acid and clethodim. Herbicide efficacy was rated and produced tubers were counted. None of the treatments achieved full control. Four weeks after application a growth reduction of 84% was observed in the glyphosate treatment, whereas bentazone reduced growth by 34% compared to the control. In the other treatments, growth reduction was < 15%. In the glyphosate and bentazone treatment, considerably fewer tubers were produced than in the control. Concluding, we could not confirm our hypothesis. Already 6 weeks after germination seedlings were well developed, tolerant to the sprayed herbicides, except for glyphosate and bentazone, and produced tubers. This implies, that already after a short time Cyperus esculentus stands originating from seeds pose the same problems as the ones originating from tubers.

Cyperus esculentus L. causes high yield losses in many crops worldwide. In Switzerland it was observed for the first time about 30 years ago. Since then it has become a serious weed in several regions - especially where vegetables are produced. Growing vegetables in heavily infested fields should be abandoned due to their low competitiveness and the lack of available, effective herbicides. Contrarily, in maize several herbicides with a partial effect on C. esculentus are registered. Thus, continuous cultivation of maize including the use of the most effective herbicides against C. esculentus could help reducing infestation levels in heavily infested fields. Field trials were carried out at two sites in maize during 2011 and 2012. Different herbicide combinations, hoeing and herbicide applications combined with hoeing were the applied treatments. Split application was compared with one single application of the same amount of product. The effect of an additional, late under leaf herbicide application was determined as well. Cyperus esculentus coverage was estimated in the fields in 2011. Plots were sampled in spring 2011, autumn 2011 and autumn 2012. The Number of C. esculentus sprouts germinated from the soil samples was determined under greenhouse conditions. The most effective herbicide combination of registered active ingredients was rimsulfuron and mesotrione. Smetolachlor was effective as well, especially if combined with mechanical weed control. Halosulfuron-methyl applied twice provided the best C. esculentus control. Split application tended to be more effective than a single application. Control of C. esculentus could be improved considerably with an additional herbicide application in late June (under leaf). The treatments with highest C. esculentus control determined in the field trials and combinations thereof are effective treatment options for C. esculentus control in maize. These findings indicate and confirm that maize cropped for several years with intensive weed control could successfully decrease C. esculentus infestation levels in farmers’ fields.

In spring 2011, two field trials on site-specific weed control in winter wheat and maize were carried out at Ihinger Hof research station of the University of Hohenheim. For the image acquisition, bi-spectral cameras were mounted on a vehicle. These cameras are able to take images free from disturbances by soil, mulch and stones. Images and the corresponding GPS-data were stored on-the-go. Afterwards, the images were analyzed by a weed recognition software. Weed infestation was mapped in consideration of weed species and weeds grouped according to their herbicide sensitivity. In order to simulate an online herbicide application, a onesided moving average of order five was used for the weed mapping. This kind of rearward calculation uses only the data of weed infestation which were already assessed behind or directly in the current position of the vehicle. The calculated weed distribution maps were checked by visual grid sampling. Herbicide application maps were generated by applying weed thresholds on the weed distribution maps. The herbicide application based on the maps was conducted by a multiple sprayer which allows the application of up to three herbicides independently from each other in a single pass across the field. Later on, the performance of the herbicide application was controlled again by visual grid sampling. Compared to a uniform herbicide application, the sitespecific weed control saved 83 % and 58 % herbicides respectively in winter wheat and 66 % in maize. The average efficacy of the site-specific herbicide application system in winter wheat was 70 % of the conventional herbicide application.