Glyphosate doses should be lower for shaded environments: light and the sensitivity of Euphorbia heterophylla

Abstract

The objective of this study was to evaluate the influence of light and glyphosate doses in the Euphorbia heterophylla control. The experiment was conducted in a factorial scheme. The first factor consisted of plants under full sunlight and two shadings of 40% and 65%, and the second factor represented by doses 0 (control), 370, 740, 1110, 1480 and 1850 g a.e. ha−1 of glyphosate. Shading increased E. heterophylla sensitivity to glyphosate compared to full sunlight. Under shading, the dose of 1110 g ha−1 of glyphosate was efficient in the management of this species, with control higher than 90%. However, under full sunlight, the highest doses achieved control levels around 75%, considered unsatisfactory. The variables fresh weight, quantum yield of photosystem II and electron transport rate of E. heterophylla showed a strong negative correlation with the species control by glyphosate. The glyphosate recommendations for controlling E. heterophylla needs to consider the light conditions in the plant growth environment, as an economically and sustainable practice in the integrated management of the specie.