ACTION OF THE PRE-EMERGENT HERBICIDE ISOXAFLUTOL ON THE INITIAL ESTABLISHMENT OF FIVE FOREST SPECIES

Abstract

The objective of this study was to evaluate the tolerance of native species from southern Minas Gerais state, commonly used in forest restoration programs through direct seeding, to the pre-emergent herbicide isoxaflutole. The species used were Cassia grandis, Anadenanthera macrocarpa, Cedrela fissilis, Hymenaea courbaril and Sesbania virgata. The herbicide treatments consisted of five doses: 0, 50, 100, 200, and 300 grams of active ingredient per hectare (g.a.i.ha^-1). The phytotoxicity symptoms were assessed during the germination process as well as the subsequent plant growth in height, stem diameter, shoot dry mass, and root dry mass. The experimental design was completely randomized, with eight replicates, conducted in pots under greenhouse conditions, with each pot considered an experimental unit. The species C. grandis, A. macrocarpa, and C. fissilis showed high sensitivity to the herbicide, with the 50 g.a.i.ha^-1 dose causing visible phytotoxic symptoms and reductions in all evaluated parameters when compared to the 0 g.a.i.ha^-1 dose, while the 300 g.a.i.ha^-1  dose resulted in 100% mortality. In contrast, for H. courbaril and S. virgata, the 50 g.a.i.ha^-1 dose promoted an increase in the evaluated parameters compared to the control (0 g.a.i.ha^-1). Although the 300 g.a.i.ha^-1 dose caused visible phytotoxic symptoms in these species, it was not sufficient to induce the plant mortality, indicating tolerance of both species to the tested herbicide doses.