Herbicide Resistance: Toward an Understanding of Resistance Development and the Impact of Herbicide-Resistant Crops

Abstract

Development of herbicide-resistant crops has resulted in significant changes to agronomic practices, one of which is the adoption of effective, simple, low-risk, crop-production systems with less dependency on tillage and lower energy requirements. Overall, the changes have had a positive environmental effect by reducing soil erosion, the fuel use for tillage, and the number of herbicides with groundwater advisories as well as a slight reduction in the overall environmental impact quotient of herbicide use. However, herbicides exert a high selection pressure on weed populations, and density and diversity of weed communities change over time in response to herbicides and other control practices imposed on them. Repeated and intensive use of herbicides with the same mechanisms of action (MOA; the mechanism in the plant that the herbicide detrimentally affects so that the plant succumbs to the herbicide; e.g., inhibition of an enzyme that is vital to plant growth or the inability of a plant to metabolize the herbicide before it has done damage) can rapidly select for shifts to tolerant, difficult-to-control weeds and the evolution of herbicide-resistant weeds, especially in the absence of the concurrent use of herbicides with different mechanisms of action or the use of mechanical or cultural practices or both.

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.…”

“…Proactive, evolutionary-based weed management options that integrate both herbicides and non-chemical tools are of utmost importance in agriculture today [14]. As resistance is generally the consequence of using a single herbicide repeatedly, any proactive or reactive approach should take an opposite view: the use of a diverse method to avoid repetition as much as possible.…”

“…Possible direct influences of HRCs acceptance on biodiversity, especially in South America, encompassed a shift in the genetic diversity of crops, expended volunteer crop issues, and induced aggression by resistant varieties of natural ranges above the farm line [36]. Also, there is a risk correlated with the probability for the exchange of genetic material between related HRCs, from the one side wild progenitors and conventional crops and weeds from the other side [37,14].…”

Growth and Development of Digitaria insularis Biotypes Susceptible and Resistant to Glyphosate

“…Selecting for herbicide-resistant weed biotypes has been usual in agricultural lands in numerous countries; management practices used in modern agriculture based on intensive use of herbicides have increasingly urged the selection of these biotypes (Beckie and Reboud 2009;Vencill et al, 2012).…”

Sulfentrazone Selectivity and Efficiency in Cassava Crops in Sandy and Clayey Soils

“…This small number of herbicides and mechanisms of action may hinder the development of tillage strategies, in addition to providing increased resistant biotypes selection pressure (Beckie, 2006;Beckie & Reboud, 2009;Vencill et al, 2012).…”