Chemical Weed Management in Grain Sorghum and Selectivity of Atrazine + S-Metolachlor to Different Hybrids

Abstract

Grain sorghum (Sorghum bicolor) is one cereal crop that faces huge problems with weed interference mostly because the lack of selective herbicides. This study aimed to assess the efficacy and safety of herbicide alternatives for weed control in grain sorghum as well as the selectivity of atrazine + s-metolachlor to different hybrids. Three field trials were designed as a randomized complete block with four replications. All experiments were conducted in Jardinópolis-SP and Mogi Mirim-SP during the 2015/16 growing season. Two trials included acetochlor, flumioxazin, fluroxypyr, mesotrione and s-metolachlor, applied in pre or post-emergence, in association or not with atrazine. A third trial was carried out with rates of the premix containing atrazine + s-metolachlor applied to the following hybrids: 1G100, 1G220, 1G230, 1G244, 1G282, 50A10, 50A40, 50A50 and 50A70. The pre-emergence herbicides that exhibited satisfactory efficacy of weed control and selectivity to sorghum crop were flumioxazin, atrazine + mesotrione and atrazine + s-metolachlor. For post-emergence, atrazine, atrazine + acetochlor, atrazine + s-metolachlor and atrazine + fluroxypyr were the best treatments for both efficacy and selectivity. The application of atrazine + s-metolachlor at the evaluated rates was considered selective to the nine hybrids assessed. MANEJO QUÍMICO DE PLANTAS DANINHAS EM SORGO GRANÍFERO E SELETIVIDADE DE ATRAZINE + S-METOLACHLOR PARA DIFERENTES HÍBRIDOSRESUMO -O sorgo granífero (Sorghum bicolor) é um dos cereais de verão que mais enfrenta problemas com plantas daninhas em razão da interferência destas espécies e carência de herbicidas para controlá-las. O objetivo deste estudo foi avaliar a eficácia e segurança de herbicidas alternativos no controle de plantas daninhas em sorgo granífero, assim como a seletividade de atrazine + s-metolachlor para diferentes híbridos. Três experimentos foram realizados em campo com delineamento de blocos ao acaso e quatro repetições, sendo conduzidos em Jardinópolis-SP e/ou Mogi Mirim-SP, ao longo da safra 2015/16. Em dois experimentos, acetochlor, flumioxazin, fluroxypyr, mesotrione e s-metolachlor foram avaliados em pré e/ou pós-