Efficacy of Irradiated Glyphosate Against Brachiaria plantaginea L.

Glyphosate irradiated with cobalt-60 type Gammacell 220 at different rates was sprayed on seedlings of Brachiaria plantaginea L., a common weed, grown in pots (one seedling with 3-4 leaves in each pot), at different concentrations equivalent to 1 L h-1 or 3 L h-1. Each sample containing 40 ml of the product (glyphosate) taken to a source of Cobalt-60 type Gammacell 220, under a dose rate of 0.312 kGy/hour in doses of: T0, control (water instead of glyphosate); T1, glyphosate at 1.0 L h-1; T2, glyphosate at 3.0 L h-1; T3, glyphosate irradiated at 250 Gy at 1.0 L h-1; T4, glyphosate irradiated at 500 Gy at 1.0 L h-1; T5, glyphosate irradiated at 750 Gy at 1.0 L h-1; and T6, glyphosate irradiated at 1000 Gy at 1.0 L h-1. The effects were assessed in terms of the extent of injury, where scale of 0% (no visible injury) to 100% (plant dead), number of tillers, weed survival and dry biomass produced by the plants. The most effective treatment was glyphosate irradiated at 250 Gy h-1 and applied at 1.0 L h-1. It is important to know that gamma radiation in glyphosate herbicide can be used without antagonistic interactions without cause resistance.