The experiments were carried out in 2001–2004. The aim of the research was to establish such chlorsulfuron dose that would be effective for Apera spica-venti control and would not be phytotoxic for winter wheat. Besides, it was performed to identify resistance of A. spica-venti biotypes appearing in the experimental fields to chlorsulfuron. The field experiments were conducted in winter wheat that were notably of A. spica-venti weedy. The fields belonged to a private farm at Karczyce and Gałów. The cereals had grown there for a long time and winter wheat monoculture together with repeated chlorsulfuron application was used. The experiments were conducted using randomized blocks method with 3 reapplications. Chlorsulfuron (Glean 75 WG) was applied at rates ranging from 1 to 4.5 times higher than the recommend field dose (15–67.5 g a.s./ha). The degree of sensitivity of A. spica-venti to chlorsulfuron was established by biological tests in greenhouse conditions. The herbicide was applied at four – leaf stage of development at rates ranging from 1 to 32 times higher than the recommend field dose (11.25–360 g a.s./ha). Poor chlorsulfuron efficacy to control of A. spica-venti or its lack might testify for resistance of this species to the herbicide. Chlorsulfuron as an active ingredient was very selective for winter wheat. An application of 67.5 g/ha of the herbicide was not harmful to growth and yielding of winter wheat. Unfortunately, even this dose of the herbicide was ineffective in control of A. spica-venti. In fields with a long-term monoculture of winter wheat together with the use of chlorsulfuron, resistance of A. spica-venti biotypes to this active ingredient was ascertained. Studies in greenhouse conditions proved that the biotypes were not damaged even when the dose was exceeded 32 times. The above confirmed the resistance of these biotypes to chlorsulfuron.

New solutions in plant protection applications are still highly desirable. Aiming at higher efficiency, environmental safety and profitability of production which, in addition to reducing the costs of the application of plant protection products, limits the destruction of soil structure combined use of agrochemicals seems to be one of the most important method in modern agriculture. In 2016 and 2017, the Plant Protection Institute – National Research Institute in Poznań, Poland, conducted field experiments on the possibility of combining two popular herbicides used to control monocotyledonous weeds: pinoxaden and fenoxaprop-P-ethyl, with a two-component plant growth and development regulator (mepiquat chloride and prohexadione calcium) on KWS Ozon winter wheat. The tested substances were applied at the BBCH 24 stage of winter wheat – herbicide only, and at the BBCH 31 stage – a mix of herbicides with a plant growth and development regulator. Regardless of the method of application of pinoxaden (herbicide only or mixed), high effectiveness of Apera spica-venti control was obtained in both years of the study. The mix of pinoxaden with mepiquat chloride and prohexadione calcium reduced the wheat crop height to a similar extent as separate application of the substances. The combined application of fenoxaprop-P-ethyl with mepiquat chloride improved the effectiveness of wheat crop height control. The method of application of the substances had no significant effect on winter wheat yield. Grain yields harvested from plots treated with the above substances were significantly higher than control only in the case of high weed infestation of winter wheat. The technological value of wheat grain depended on the year of study, while the method of application did not have a significant impact on the evaluated parameters.