Resposta de duas gramas-boiadeira (Leersia hexandra Sw. e Luziola peruviana Juss.) ao herbicida glyphosate

Abstract

The southern cutgrass and peruvian watergrass are perennial weeds frequently found in paddy areas in southern Brazil. The control of these species is done in the winter and/or on the pre-planting of rice through the association of chemical and mechanical methods. However, in recent years, chemical control of these species with the use of non-selective herbicides such as glyphosate, has not been efficient in moist or poorly drained areas, a common situation found in flooded rice fields. In this context, the investigation of the efficiency of glyphosate to control this weeds is very important, since there are not herbicides commercially available to control this species in post-emergence applications of the rice crop. Therefore, the objectives of this study were: (i) to evaluate southern cutgrass and peruvian watergrass sensitivity to different formulations of glyphosate (Chapter I), (ii) evaluate southern cutgrass and peruvian watergrass control with different formulations of glyphosate at different soil moisture levels (Chapter II). Based on the results obtained it was concluded that these species exhibit differential sensitivity to glyphosate been Leersia hexandra is more sensitive than Luziola peruviana. Glyphosate formulation influences control efficiency, where Transorb Roundup® is more effective in controlling Luziola peruviana. Transorb R Roundup® and Roundup Ultra® provide the best control of the two species. The soil moisture content affects glyphosate efficacy, and the control of the both species is difficult in flooded soil conditions. At flooded soil condition Luziola peruviana has 10 increased tolerance to glyphosate compared to other soil moisture níveis and Leersia hexandra.