Viabilidade de sementes de azevém em função do estádio fenológico de aplicação de herbicidas

Ryegrass is an important weed in maize crops and winter cereals. The emergence of glyphosate-resistant biotypes, the main herbicide used in the Brazilian agricultural system, and the ability of natural reseeding, have raised the need to seek alternatives to minimize seed bank replenishment of this species. The objective of this study was to evaluate the effect of herbicide application at different growth stages of glyphosate-sensitive ryegrass plants on the viability of seeds from these plants. To this end, ryegrass plants were submitted to the application of glyphosate and clethodim association (750 g a.e. ha -1 + 120 g a.i. ha -1 , respectively) in 10 in different development stages. The seeds produced were evaluated for their viability in tetrazolium test and germination in a B.O.D (Biochemical Oxygen Demand)-type growth chamber, with subsequent tetrazolium test and plants emergence in peat substrate. The results indicate that desiccation time limit for ryegrass to not produce viable seeds is the stage prior to complete anthesis, and at this stage there was complete reduction of viability, germination and emergence of ryegrass seeds exposed to the application of glyphosate + clethodim association.