Can Control of Glyphosate Susceptible and Resistant Conyza sumatrensis Populations Be Dependent on the Herbicide Formulation or Adjuvants?

Abstract

In this work, we studied the effect of three glyphosate formulations (isopropylamine, ammonium and potassium salts) and two non-ionic adjuvants on the resistance response of two resistant (R1, R2) and one susceptible population of the highly invasive Asteraceae, Conyza sumatrensis, from Southern France vineyards. Only in R1, an amino acid substitution (Pro106Thr) was found in the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). The two adjuvants, in a similar fashion, significantly reduced GR50 values for every population and glyphosate formulation. Without adjuvants, glyphosate as potassium salt was the only formulation able to significantly reduce the GR50 values of every population. For every population, the two adjuvants improved, indistinguishably, leaf retention of the herbicidal solution and the potassium salt formulation led to the highest retention, both with and without the adjuvant added. Uptake responses paralleled those of retention and adjuvant addition was more effective in increasing foliar uptake of the lower performing formulations (isopropylamine and ammonium salts). The allocation pattern of glyphosate among plant compartments was only dependent on population, with R2 retaining most glyphosate in the treated leaf, clearly suggesting the occurrence of a Non-Target Site Resistance (NTSR) mechanism. Results indicate that control of weed populations possessing NTSR mechanisms of resistance to glyphosate may be improved through adequate selection of formulation and adjuvant use.

Microbial Biosurfactant: A New Frontier for Sustainable Agriculture and Pharmaceutical Industries

“…Still, drift does not reach the target site and shows poor efficacy against disease management [ 132 ]. However, nowadays, to improve the effectiveness of pesticides applications, the delivery mechanism has been upgraded via adding surfactants, nano-based formulations, and improved spraying technology [ 133 , 134 ]. In general, during pesticide application, surfactants have been used as an additive or adjuvants and mixed with pesticides that help in dispersion, emulsification, better spreading, or increasing the contact area with the plant surface, which enables the pesticides to better reach the target pests or target organisms [ 135 ] ( Figure 4 ).…”

Sustainable Crop and Weed Management in the Era of the EU Green Deal: A Survival Guide

“…The same authors suggested that the combination of plant extracts with reduced rates of herbicides is a cost-effective approach for weed management in wheat. Similarly, the integration of adjuvants into herbicide tank mixtures is a promising method to reduce herbicide input or increase herbicide efficacy and achieve high levels of weed control, something quite desirable against herbicide-resistant weeds [103]. The formulation of some active ingredients, such as glyphosate, should be also considered to avoid spraying failures [104].…”

Early detection, herbicide resistance screening, and integrated management of invasive plant species: a review

“…96 For systemic herbicides, such as glyphosate, the herbicide resistance tests include analysis of the biokinetics in the whole plant. 97,98 An analytical review with technologies up to 2013 gathers all relevant knowledge on the available tests and methods for confirmation of herbicide resistance. 99 In Table 4, several recent onfarm, portable, and rapid diagnostic tests for herbicide resistance reported after 2013 are presented in detail to assist the screening of IPS for putative herbicide resistance.…”