Rapid Evolution of Herbicide Resistance by Low Herbicide Dosages

Abstract

Herbicide rate cutting is an example of poor use of agrochemicals that can have potential adverse implications due to rapid herbicide resistance evolution. Recent laboratory-level studies have revealed that herbicides at lower-than-recommended rates can result in rapid herbicide resistance evolution in rigid ryegrass populations. However, crop-field-level studies have until now been lacking. In this study, we examined the impact of low rates of diclofop on the evolution of herbicide resistance in a herbicide-susceptible rigid ryegrass population grown either in a field wheat crop or in potted plants maintained in the field. Subsequent dose–response profiles indicated rapid evolution of diclofop resistance in the selected rigid ryegrass lines from both the crop-field and field pot studies. In addition, there was moderate level of resistance in the selected lines against other tested herbicides to which the population has never been exposed. This resistance evolution was possible because low rates of diclofop allowed substantial rigid ryegrass survivors due to the potential in this cross-pollinated species to accumulate all minor herbicide resistance traits present in the population. The practical lesson from this research is that herbicides should be used at the recommended rates that ensure high weed mortality to minimize the likelihood of minor herbicide resistance traits leading to rapid herbicide resistance evolution.

Geographic Distribution of Ryegrass Resistent to the Clethodim Herbicide in Rio Grande do Sul1

“…However, recent studies have shown that recurrent selections with reduced doses (smaller than the registered dose) of ACCase inhibitor herbicides result in a rapid evolution of the resistance to herbicides in only three generations (Neve & Powles, 2005;Manalil et al, 2011). The susceptibility difference found in the 14 biotypes that survived the application of half the herbicide dose may be a result of the use of low doses, such as 72 at 84 g i.a.…”

Winter wheat yield loss in response to Avena fatua competition and effect of reduced herbicide dose rates on seed production of this species

“…These results show that A. fatua seed production was not directly related to residual biomass and thus herbicide efficacy, but dependent on interaction with the crop and herbicide mode of action. Avena fatua seed production after application of reduced herbicide dose rates is bearing the risk of herbicide resistance development, in particular non-target-site resistance [10,28]. Cases of herbicide-resistant A. fatua have been reported for several European countries such as Belgium, France, Germany, Poland, UK and Turkey [29].…”

“…However, GonzalezAndujar et al [8] demonstrated that Avena sterilis plants produce more panicles at reduced herbicide dose rates. This might cause a shift in weed population towards less herbicide-sensitive individuals in the following generations [9,10].…”

Introductory Chapter: Actual Issues (Moments) in Herbicide Resistance Weeds and Crops

“…From an evolutionary perspective, many factors influence the dynamics of herbicide-resistant evolution under herbicide selection [12,13]. One crucial factor in herbicide-resistant evolution is the selection pressure caused by the repeated use of herbicides with the same mechanism of action in conventional crop cultivars [14], of which a major determinant is the herbicide use rate [15]. The use of an herbicide (or herbicides from the same herbicide group) continuously for many years can drastically decrease the number of susceptible biotypes within the natural weed population and dramatically increase the number of resistant biotypes.…”