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Die Verringerung der Menge an Herbiziden, die für die Landwirtschaft verwendet werden, gewinnt an Zugkraft, da ein beträchtlicher Anteil der Konsumenten herbizidfreie Kulturen bevorzugen würde. Die Entwicklung von praxistauglichen und kostengünstigen Alternativen muss jetzt intensiviert werden. Fortschritte in den Bereichen Computer-Vision und Robotik ermöglichen neue Ansätze für eine hochpräzise Unkrautkontrolle in Reihenkulturen wie Soja und Zuckerrüben. Ziel ist, Unkräuter während der sensiblen Wachstumsstadien der Kulturpflanze zu regulieren. Im Rahmen dieser neuen Möglichkeiten wurden Blaulicht-Diodenlaser auf ihre Wirksamkeit untersucht. Nach dem Auflaufen der Kulturpflanzen wurden die Unkräuter sieben Mal im Abstand von 3-5 Tagen bestrahlt. Bei Reihenschluss waren die Flächen unkrautfrei und wurden bis zur Ernte nicht weiter behandelt. Die Methode ist für die Landwirtschaft interessant, da Unkräuter effektiv und präzise kontrolliert und gleichzeitig die Kulturpflanzen in der Nähe geschont werden.

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.

The concept of integrated pest management (IPM) has proven successful, however challenges in implementing IPM strategies remain. Furthermore, detailed investigations are needed to elucidate the performance and tradeoffs of combined practices along entire crop rotations. In the framework of efforts to reduce the use of pesticides in Swiss agriculture, IPM in arable crops will be further developed in an on-farm project starting in autumn 2019. The overall aim of the project is to reduce pesticide use by 75% with a maximum yield loss of 10%. Preventive and alternative practices supporting natural control of noxious organisms (pathogens, pests, weeds) such as cover crops, intercropping, flower strips and biological control agents will be implemented and investigated in different 6-year crop rotations in a network involving 75 farms. The project involves scientists, farmers and extension services in a co-innovation process in five regions of the Swiss plateau. Effectiveness of the practices on weeds, diseases, pests and beneficials will be closely monitored and evaluated along the entire crop rotation.

The growth repressive effect of common buckwheat (Fagopyrum esculentum) on redroot pigweed (Amaranthus retroflexus) was studied by separating resource competition from root interactions between the two plant species in a pot trial in the phytotron. In order to verify this result in situ field trials were performed. A strong repression of redroot pigweed growth by buckwheat could be observed independently of shading. However, soil both from the field and phytotron trials in which buckwheat had been growing didn’t have an effect on redroot pigweed and lettuce (Lactuca sativa) growth. Assuming that allelopathic compounds are present in the soil solution supplementary experiments were conducted. Lettuce root length was measured after exposing seeds to different “buckwheat soil” extracts. Moreover, buckwheat and lettuce developed at the same time next to each other in petri dishes. In none of the experiments an influence on lettuce and redroot pigweed development could be observed. We conclude that there are either no allelopathic molecules in the soil solution (not soluble in water) or that they are rapidly degraded. The observed growth inhibiting effect seems to be due to a long term and constant exposure of small quantities of allelopathic molecules. However, it is also possible that growth repression of redroot pigweed by buckwheat is not due to allelopathy.

Yellow Nutsedge (Cyperus esculentus L.) belongs to the family of Cyperaceae. It propagates exclusively with tubers in the ground. Its abundance has strongly increased in Switzerland in the last two decades. Main reasons for this increase are changing land use and production systems, a difficult herbicide control and a low awareness level among the farmers. The actual invasion is enhanced by unintended dislocation of tubers by machines or crops/crop waste, lack of knowledge of infested fields and missing supporting measures. An obligation to announce infested fields and to control Yellow Nutsedge is currently discussed in Switzerland. Such an obligation would help contractors and buyers of crops to reduce unintended dislocation of tubers. Cleaning up infested plots is quickly expensive and complex. Maleic acid hydrazide is actually used for preventing potato tubers to germinate in stock. We tested Fazor (maleic acid hydrazide) and Asulox (asulam) for its efficacy on preventing germination of Yellow Nutsedge tubers. The results of our pot trial in the greenhouse are clear. The expected efficiency was not observed. Furthermore the complexity of problems with this species in agriculture is discussed and some ideas for a control strategy are given in this paper.

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Copyright of Julius-Kühn-Archiv is the property of Julius Kuehn Institut and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)