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Publication Date

1977

Description

The effect of 2,4-D and 2,4,5-T at 0.08, 0.16, 0.32, and 0.48 per cent concentration in 7001/ha water on the resistance of young and old trop­ical legumes, and the effect of dalapon at 4 and 8 kg/ha and of glyphosate at l and 2 kg/ha in 1125 1/ha water on the resistance of the old tropical grasses were assessed. Amongst the legumes, stylo showed the highest resistance and siratro the least, both at young and old stages of growth, followed by puero and Greenleaf desmodium at the old stage, especially at lower rate of application of 2,4-D. The effect of 2,4,5-T was more lethal than that of 2,4-D, and its use should be discouraged. In grasses, glyphosate was more damaging than dalapon, even at the lowest rate of application. Amongst the grasses, Mo­lopo buffel and hamil showed less than fifty per cent damage from glyphosate at the lower rate, but setaria and green panic appeared to be more sensitive. Dalapon at lower rate shows good promise of grassy weeds control in tropi­cal grasses. Although these results need further confirmation under individual conditions, it is clear that application of 2,4-D and dalapon can be quite useful in controlling some weeds in tropical pastures without causing serious damage to pasture species.

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Resistance of tropical pasture species to herbicides

The effect of 2,4-D and 2,4,5-T at 0.08, 0.16, 0.32, and 0.48 per cent concentration in 7001/ha water on the resistance of young and old trop­ical legumes, and the effect of dalapon at 4 and 8 kg/ha and of glyphosate at l and 2 kg/ha in 1125 1/ha water on the resistance of the old tropical grasses were assessed. Amongst the legumes, stylo showed the highest resistance and siratro the least, both at young and old stages of growth, followed by puero and Greenleaf desmodium at the old stage, especially at lower rate of application of 2,4-D. The effect of 2,4,5-T was more lethal than that of 2,4-D, and its use should be discouraged. In grasses, glyphosate was more damaging than dalapon, even at the lowest rate of application. Amongst the grasses, Mo­lopo buffel and hamil showed less than fifty per cent damage from glyphosate at the lower rate, but setaria and green panic appeared to be more sensitive. Dalapon at lower rate shows good promise of grassy weeds control in tropi­cal grasses. Although these results need further confirmation under individual conditions, it is clear that application of 2,4-D and dalapon can be quite useful in controlling some weeds in tropical pastures without causing serious damage to pasture species.