Differential tolerance of four tree species to glyphosate and mesotrione used in agrosilvopastoral systems

Abstract

Agrosilvopastoral systems present high potential as a sustainable agriculture technique, despite the current limiting points in the systems management that must be overcome. A major bottleneck in the implementation of these systems is the damage caused, to forest species, by the application of herbicides for weed control in the crop component. The present study evaluated the selectivity of herbicides in seedlings of two tree species native to the Brazilian Cerrado, Dipteryx alata (Vog.) and Anadenanthera colubrina var. cebil (Griseb.) Altschul, and two eucalyptus clones, E. urograndis and E. urocam. The study was conducted in a greenhouse, with two commonly-used herbicides (glyphosate and mesotrione), in five different doses. The sensitivity of tree species to the herbicides was evaluated through physiological, morphological and visual phyto intoxication characteristics. For glyphosate, the tree species exhibited strong phytotoxicity symptoms from the second day after application, being the symptoms more prominent in the two eucalyptus clones and less in D. alata, which presented higher tolerance to this herbicide. For mesotrione, the four tree species studied showed mild toxicity symptoms, with very little or absent significant impacts in growth and biomass accumulation. The herbicide mesotrione was shown to be selective for the four tree species studied and can be recommended to agroforestry systems in which these species are present. These results based on phytotoxicity grades are reinforced by the biometric and physiological parameters measured.