Efficacy of atrazine + simazine in post-emergence controI of weeds in maize, in Brazilian Cerrados

Abstract

A trial was carried out to test the efficacy of formulations and doses of atrazine + simazine, in post-ernergence on maize (cv. BR-201). The following treatrnents were tested in a sandy Latosoil, in Uberaba, Brazil: Primatop 500 se (atrazine 250g/1 + sirnazine 850 g/l) at the doses of2500, 3000 and 3500 g/ha and Prirnatop 80 PM (atrazine 400 g/I + simazine 400 g/I) at the doses of2400, 3200 and 3600 g/ha, plus mineral oil (0.25% v/v); Triamex se (atrazine 250 g/l +sirnazine 250 g/I) at the dose of3000 g/ha; hand weeding and no control. There was no difference between treatrnents concerning the plant density, number of cobs and height ofthe first cob. The highest yield (3512 kg/ha) was observed with the application ofPrimatop 80 PM at 3200 g/ha and Triamex. The lowest seed weight was observed with Primatop 80 PM at 3500 g/ha. There was no difference between the herbicides and hand weeding concerning plant height. The best index for mechanical harvesting (98.0 - 98.5%) was achieved with Primatop 500 SC at 3000 and 3500 g/ha, Primatop 80 PM at 3200 and 3600 g/ha and Triamex. The best control of Digitaria horizontalis was achieved with Primatop 80 PM at 3600 g/ha (98.5%) and Primatop 500 SC at 3500 g/ha (98.0%), but the other doses of these formulations also showed excellent control of this species. The best control of Eleusine indica was obtained with Primatop 80 PM at 3600 giba (99.5%), Primatop 80 PM at 3200 giba + mineral oil (98.5%) and Primatop 500 SC at 3500 giba (98.0%). Primatop 500 se and Primatop 80 PM showed an excellent control of Borreria alata and Acanthospermum australe at 65 days after application, in ali tested doses. No symptom offitotoxicity was observed on maize after herbicide application.