Sensitivity Analysis of Italian Lolium spp. to Glyphosate in Agricultural Environments.

Silvia Panozzo,Maurizio Sattin,Alberto Collavo

doi:10.3390/plants9020165

Silvia Panozzo, Maurizio Sattin + Show 1 more

Open Access

https://doi.org/10.3390/plants9020165

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Abstract

Empirical observations generally indicate a shifting and decreased Lolium spp. susceptibility to glyphosate in Italy. This is likely due to the long history of glyphosate use and to the sub-lethal doses commonly used. There is, therefore, a need to determine the variability of response of Lolium spp. to glyphosate and identify the optimum field dose. To perform a sensitivity analysis on Lolium spp. populations in an agriculture area, collection sites were mainly chosen where glyphosate had not been applied intensely. Known glyphosate-resistant or in-shifting populations were included. Two outdoor dose-response pot experiments, including eleven doses of glyphosate, were conducted. The dose to control at least 93%–95% of susceptible Lolium spp. was around 450 g a.e. ha−1. However, to preserve its efficacy in the long term, it would be desirable not to have survivors, and this was reached at a glyphosate dose of 560 ± 88 g a.e. ha−1. Taking into account the variability of response among populations, it was established that the optimal dose of glyphosate to control Lolium spp. in Italy up to the stage BBCH 21 has to be at least 700 g a.e. ha−1. As a consequence, it is recommended to increase the label recommended field rate for Lolium spp. control in Italy to a minimum of 720 g a.e. ha−1.

Highlights

Lolium rigidum Gaud. and Lolium multiflorum Lam. (Italian ryegrass, LOLMU) are two self-incompatible species that have a global distribution [1]
The aims of this research were (1) to determine the variability in glyphosate response of Lolium spp. populations collected from Italian agricultural environments and (2) to determine the glyphosate dose that is effective on the Lolium spp. populations in field conditions in order to preserve its efficacy in the long term
Two outdoor pot dose-response experiments were performed during spring (March-May) and autumn (September-November) to test the effects of increasing glyphosate dose on plant survival and fresh weight for several Lolium spp. populations collected from Italian agricultural environments

Summary

Introduction

Lolium rigidum Gaud. (rigid ryegrass, LOLRI) and Lolium multiflorum Lam. (Italian ryegrass, LOLMU) are two self-incompatible species that have a global distribution [1]. (rigid ryegrass, LOLRI) and Lolium multiflorum Lam. According to reported cases [2], they are among the species most prone to evolve herbicide resistance. L. rigidum populations resistant to 13 different herbicide. L. multiflorum occurs in several temperate countries and populations resistant to nine different herbicide SoA have been reported [4]. Both species originated from the Mediterranean, have a C3 photosynthetic pathway and produce dense infestations [5]. The two species are often mixed in the field and not always identifiable, and in those cases, the population is defined as LOLSS (Lolium species)

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