Effects of Sublethal Doses of Herbicides on the Competitive Interactions Between 2 Nontarget Plants, Centaurea cyanus L. and Silene noctiflora L.

Abstract

Plant competitive interactions influence the effect of herbicides, and the effect of competitive interactions on plant responses may be important to include in the ecological risk assessment of herbicides. In the present study the effect of competitive interactions and sublethal doses of 2 herbicides on plant species was investigated in competition experiments and fitted to empirical competition models. Two nontarget species commonly found in agroecosystems (Centaurea cyanus L. and Silene noctiflora L.) and 2 herbicides (glyphosate and metsulfuron methyl) were used in separate experiments. Plants were sprayed at the 6‐ to 8‐leaf stage. Effects of herbicide treatments and plant density were modeled by generalization of a discrete hyperbolic competition model. The 10% effective dose (ED10) was calculated for C. cyanus. All experiments showed that as density increased, plants were negatively affected. Furthermore, in all cases, C. cyanus remained a better competitor than S. noctiflora. Nevertheless, the density of S. noctiflora (competitor) was an influential element in determining the ED10 of C. cyanus measured at the mature stage. With herbicide exposure, the competitive interactions were further altered; C. cyanus was less affected by glyphosate when S. noctiflora increased to high density. In contrast, at the young stage, conspecific density was important in determining the sensitivity of C. cyanus to metsulfuron methyl, whereas the density of the competitor S. noctiflora had a limited influence. Overall, the results demonstrate the importance of integrating the effect of herbicide and species interactions measured at the reproductive stage into the ecological risk assessments of pesticides. Environ Toxicol Chem 2019;38:2053–2064. © 2019 SETAC.

Effect of interspecific competition on species sensitivity distribution models: Analysis of plant responses to chemical stress

“…Such a question is however essential for sessile organisms like plants, since they need to be tolerant to all local negative environmental conditions to survive and maintain their population. Results mainly highlighted the existence of interactions between chemical stress responses and competitive interactions between plant species (Boutin et al [2019], Damgaard et al [2014]), reinforcing the need to take into account such biotic interactions in ERA procedures.…”

How does interspecific competition modify the response of grass plants against herbicide treatment? A hierarchical concentration-response approach

“…Despite recent advances [Boutin et al, 2019;Damgaard et al, 2014], the effects of competition on plant response to chemical stress remain poorly characterised. In this work, we modelled in a single modelling framework data from monospecific bioassays in presence and absence of competitor for six phylogenetically close species.…”

“…Even if this biotic constraint has been largely studied [Aschehoug et al, 2016], studies of its interactions with chemical stress remain scarce. For example, Boutin et al studied how sublethal doses of two herbicides (glyphosate and metsulfuron methyl) could modify the competitive interactions between two plants (Centaurea cyanus L. and Silene noctiflora L.) [Boutin et al, 2019]. The results showed that competitive ability of S.…”

Herbicide Resistance and Management Options of Papaver rhoeas L. and Centaurea cyanus L. in Europe: A Review

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