Selectivity of herbicides for seedlings of tree species

Abstract

The scarce knowledge about the behavior of seedlings of native forest species relative to sensitivity to herbicides associated with the current strategies for restoring degraded natural ecosystems justifies the execution of studies to assist in this management. This study aimed to evaluate the initial selectivity of two herbicides at three different doses for 80 species that occur in seasonal semideciduous forests and are widely used in restoration projects. Two experiments were conducted to evaluate the herbicides oxyfluorfen (Experiment I) and sulfentrazone (Experiment II) at commercial dose, half the dose, and double the dose, as well as control without herbicide application. The experimental design of each experiment was completely randomized, with four replications. The percentage of phytotoxicity following a specific scale in the weed science field was evaluated at 7, 14, 21, 28, and 35 days after treatment application (DAT), while the shoot dry mass was evaluated at 35 DAT. Most native species were classified in the range of 0–10% phytotoxicity for both herbicides. Considering phytotoxicity, the herbicide oxyfluorfen negatively affected the species Inga uruguensis, Erythroxylum argentinum, Pterogyne nitens, Miconia rigidiuscula, and Simira sampaioana. Sulfentrazone showed harmful effects on the species Myrciaria vexator, Piptadenia gonoacantha, Lonchocarpus campestris, Erythroxylum argentinum, Cariniana legalis, Randia armata, Inga vera, Solanum granulosoleprosum, Cupania vernalis, Seguieria langsdorffii, S. sampaioana, Maytenus gonoclada, and Handroanthus ochraceus. Only the species R. armata, Croton floribundus, and I. uruguensis showed a reduction in dry biomass relative to the control. Therefore, the herbicides oxyfluorfen and sulfentrazone can be recommended for weed management for most of the species studied in this study, except those listed above.

Keywords: sulfentrazone; oxyfluorfen; phytotoxicity; forest management; reforestation