Browsing by Person "Klauk, Benjamin"

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Integration of cultural practices and chemical control in a management strategy against multiple herbicide-resistant Alopecurus myosuroides (Huds.)
(2024) Klauk, Benjamin; Gerhards, Roland
Weed control has been a key component of crop protection since the dawn of arable farming. Labour-intensive methods were gradually replaced by mechanisation and the discovery of herbicides, particularly in developed countries. The introduction of herbicides was accompanied by the development of resistance, which is the genetic ability of plants to survive the dose applied. In Europe, the spread of resistance in Alopecurus myosuroides (Huds.) has been observed for decades. The economic optimisation of arable farming by increasing the proportion of winter crops in the rotation and the often early sowing of these crops, as well as the consistent conducting of conservation tillage, have enabled the spread of A. myosuroides. Such systems, based on effective herbicides, are often no longer effective, partly due to the spread of multiple herbicide-resistant biotypes, which are threatening profitable arable farming. Instead, strategies that integrate both cultural practices and effective herbicides are needed, particularly where post-emergence herbicides are ineffective. The introduction of cinmethylin, an active ingredient from rice that can be used selectively in cereals against weeds, would broaden the spectrum of pre-emergence herbicides in European cereal production. The aim of this thesis was to develop a strategy to minimise the presence of A. myosuroides on sites where multiple herbicide-resistant biotypes are present. Cultural practices were combined with an herbicide regime based on cinmethylin and other active ingredients. The first paper focuses on the evaluation of three strategies, which differ in the extent of preventive and competitive cultural practices against A. myosuroides (crop rotation, tillage, sowing date, stale seedbed, cover cropping), regarding their reduction potential against an A. myosuroides population with a high proportion of biotypes with ACCase and/or ALS target site resistance. From 2017 to 2020, these three strategies were tested at two German sites with high levels of multiple herbicide-resistant A. myosuroides biotypes. Cinmethylin was used in winter wheat, winter barley and winter oilseed rape, in combination with flufenacet in winter barley and metazachlor in winter oilseed rape. Apart from propyzamide in winter oilseed rape, no herbicides were applied post-emergent. The strategy with the highest number of cultural practices (maize in rotation, inversion tillage at the beginning of the trial, delayed sowing combined with a stale seedbed in winter wheat) resulted in a significant reduction in A. myosuroides density of up to 90% compared to a strategy which resembled the usual cultivation practices (conservation tillage, only winter crop in rotation). In addition, a significantly greater reduction in the potential of viable A. myosuroides seeds was observed at one of the two sites in the strategy with the highest level of preventive and competitive cultural practices in terms of A. myosuroides control. The field trials showed that A. myosuroides populations can be controlled by adjusting overall crop management in combination with cinmethylin and other active ingredients. The second paper postulated that the efficacy of cinmethylin against A. myosuroides is increased by later application in the autumn associated with the delayed sowing of winter cereals. In four trials over three years, winter barley and winter wheat were sown at four different dates (from mid-September to the end of October). Flufenacet was included as a second option alongside cinmethylin. For both active ingredients and cereal species, the highest efficacy against A. myosuroides (over 90%) was achieved when cereals were sown in mid to late October. The hypothesis that delayed sowing improves the efficacy of pre-emergence herbicides against A. myosuroides was confirmed. This allows the remaining active ingredients to be used efficiently in strategies against multiple herbicide-resistant species. An effective method of controlling A. myosuroides is to use the post-harvest period in autumn to reduce seed supply. Seed germination induced by seedbed preparation increases the number of A. myosuroides plants that are removed by subsequent glyphosate applications. Possible policy restrictions on the use of such non-selective active ingredients require a comparison of alternatives, such as electrophysical methods with chemical and mechanical control of A. myosuroides. The third article compares mechanical (disc harrow, rotary harrow, cultivator), chemical (pelargonic acid, maleic hydrazide, glyphosate) and electrophysical (XPower®, different speeds) methods for use in stale seedbed. Glyphosate application had the lowest density of A. myosuroides heads compared to the mechanical and electrophysical methods (especially at speeds higher 3 km/h). The economic evaluation of all methods showed high costs for the chemical alternatives to glyphosate, up to 429 €/ha. The calculated maximum investments costs for an electrophysical technology are mostly in the negative range due to high process costs, which makes the use of the tested process to control A. myosuriodes before sowing unrealistic. If the use of glyphosate is banned, mechanical control of emerged A. myosuriodes plants before sowing is recommended. The results of the present thesis demonstrate the possibility of controlling A. myosuroides populations with multiple herbicide-resistance to post-emergence herbicides through a strategy that combines preventive and competitive cultural practices measures against A. myosuroides with active ingredients such as cinmethylin.