Intraregional and inter‐regional variability of herbicide sensitivity in common arable weed populations

Abstract

The question on intraregional versus inter-regional variability in herbicide sensitivity for weed populations is of major importance, both in extrapolation of model parameters and in herbicide zonal approval procedures. We hypothesised that inter-regional variability in herbicide sensitivity for field populations would be the same as intraregional variability for regions with similar climatic conditions. Seeds of field weed populations were collected in a Danish, German and Polish region. Herbicide sensitivity was tested in doseresponse experiments in the glasshouse with flufenacet and iodosulfuron (Apera spica-venti), florasulam and tribenuron (Tripleurospermum inodorum), diflufenican, diflufenican + flurtamone and pendimethalin (Viola arvensis). ED 50 values and variance components of the ED 50 values were estimated to describe the influence of region, year and population. The regions accounted for a maximum of 26% of the variance and always less than the variance accounted for by individual populations. Sensitivity indices (SI 50 ) were calculated as the ratio between ED 50 of the test population and a reference population. There was considerable intraregional variability in SI 50 values and SI 50 values from a single region did not consistently differ from other regions. The large intraregional variability in herbicide sensitivity between populations, with no evidence of resistance, is of interest both for zonal evaluation of herbicides and resistance research. For practical weed management, we conclude that dose-response functions can be transferred between the study regions, for example for the common use in decision support systems with proper insurance for the control of less sensitive populations.

First cases of herbicide resistance of Tripleurospermum inodorum in the Czech Republic

“…We noted plants that survived a 10-fold dose with almost no damage in both of these populations. In a study conducted by De Mol et al (2015), herbicide sensitivity with florasulam and tribenuron was tested in dose-response experiments for T. inodorum collected from three different European countries (Denmark, Germany and Poland). According to their studies, for tribenuron, RF values ranged from 0.24 to 2.71 (De Mol et al 2015).…”

“…In a study conducted by De Mol et al (2015), herbicide sensitivity with florasulam and tribenuron was tested in dose-response experiments for T. inodorum collected from three different European countries (Denmark, Germany and Poland). According to their studies, for tribenuron, RF values ranged from 0.24 to 2.71 (De Mol et al 2015). In another study conducted by Pannacci et al (2010), the ED50 values for tribenuron applied to the scentless mayweed population from Denmark were found to be 0.13 g a.i./ha.…”

Spatial Distribution of Acetolactate Synthase Resistance Mechanisms in Neighboring Populations of Silky Windgrass (Apera spica-venti)

“…An RI value of 10 or higher has been acknowledged as the threshold to confirm resistance (Herbicide Resistance Action Committee [HRAC] 2016) but remains under debate (de Mol et al 2015; Paterson et al 2002). Resistance confirmation based on RI values relies heavily on the susceptible reference population, and it is known that susceptible populations of silky windgrass can show large natural variation in ED 50 to a new ALS herbicide (de Mol et al 2015; Espeby et al 2011). It is very difficult to confirm early evolution of resistance in populations with low levels of resistance, which is the aim of this study, using this method.…”

Sensitivity Analysis of Alisma plantago-aquatica L., Cyperus difformis L. and Schoenoplectus mucronatus (L.) Palla to Penoxsulam

“…It has also been proven that a weed population is often resistant not only to the main selecting agent, but also to herbicides having the same SoA [12,13], even before they were marketed. Therefore, if a new herbicide having a certain SoA is introduced in a cropping system where the selection pressure exerted by other herbicides with the same SoA has already been acting, the baseline approach is not correct; a sensitivity analysis should instead be performed to elucidate the efficacy of the new herbicide in various environmental and agronomic conditions and with different weed populations [14]. This is particularly important for weed species where resistance is widespread, such as A. plantago-aquatica, C. difformis, and S. mucronatus to ALS inhibitors.…”

“…It has been stressed that the lack of new herbicide SoA [15] together with the loss in some countries of older ones with unique SoA due to stricter regulations [16], make the preservation of the efficacy of available herbicides a top priority. Determination of baselines or sensitivity analysis to widely-used herbicides can significantly contribute to this, as well as provide useful data in relation to the possible reduction of herbicide doses [14,17]. However, their determination through large dose-response experiments including many populations is costly and time-consuming, so available data are scarce.…”