O milho com tolerância ao herbicida glyphosate (Roundup Ready®) (milho RR®) vem sendo cada vez mais empregado, uma vez que propicia o uso deste herbicida para o controle de plantas daninhas. Assim o objetivo do trabalho foi avaliar a tolerância do híbrido 2B810PW (RR2/LL), submetido à aplicação de glyphosate, glufosinate e atrazine, isolados e associados em pós-emergência (V4). O ensaio foi realizado no campo, na safra 2013/14, e o delineamento adotado foi de blocos casualizados, com quatro repetições. Os tratamentos constituíram-se da aplicação de glyphosate (1080 g ha-¹ de equivalente ácido - e.a.), glufosinate (500 g ha-¹ de ingrediente ativo - i.a.), atrazine (2000 g ha-¹ i.a.), glyphosate + glufosinate, glyphosate + atrazine, glufosinate + atrazine, glyphosate + glufosinate + atrazine, além da testemunha sem aplicação. Foram avaliadas fitointoxicação aos 7, 14, 21 e 28 dias após a aplicação (DAA) e índice SPAD, aos 21 e 28 DAA. Também foram avaliadas variáveis relacionadas ao desempenho agronômico: altura, altura de inserção da espiga, diâmetro do colmo, massa de mil grãos e produtividade. Em geral, as variáveis não foram afetadas pelos tratamentos. O híbrido de milho 2B810 PW apresentou-se tolerante, para a aplicação em pós-emergência (V4) dos herbicidas nas doses utilizadas.

The goal was to evaluate the tolerance of maize hybrids 2B810 PW and 30F35 HR to herbicides applied alone and in combination. Trials were carried out in the field in a randomized block design with four replicates. The treatments were three herbicides, alone or in combination, in addition to the control. Herbicides were: atrazine (2000 g ai ha-1); nicosulfuron (50 g ai ha-1) and glyphosate (1080 g ae ha-1). Crop injury was evaluated at 7, 14, 21, and 28 days after application and also SPAD index, height, ear height, stem diameter, 1000-grain weight, and yield. In general, the variables were not affected by the treatments. Hybrids 2B810 PW and 30F35 HR showed tolerance to the application in post-emergence (V4) of the herbicides used.

Selectivity index is a way of assessing the discrimination of herbicide to a given crop by observing its effects on the crop and the weeds. The aim was to obtain the selectivity index of indaziflam herbicide to sugarcane cultivar IACSP95-5000 as a function of five weed species in two soils textures. The experiment was carried out in a greenhouse at Piracicaba, São Paulo, Brazil. The treatments consisted of indaziflam doses (0; 12.5; 25; 50; 100; 200; 400; 800 and 1,600 g of the active ingredient (ai) ha-1), applied in pre-emergence of the sugarcane and of the weeds Urochloa decumbens, Urochloa plantaginea, Digitaria horizontalis, Panicum maximum and Rottboellia cochinchinensis. In sandy loam soil, a 100% control for all weeds was provided at 25 g ai ha-1. In clay soil, for D. horizontalis the 90% reduction in total dry mass (ED90) was obtained at 25 g ai ha-1, for R. cochinchinensis at 193 g ai ha-1, for U. plantaginea at 152 g ai ha-1, for P. maximum at 124 g ai ha-1, and for U. decumbens at 94 g ai ha-1. Indaziflam was selective to IACSP95-5000 in both soils, with 10% of reduction in dry mass (ED10) at 137 g ai ha-1 for soil with a sandy loam texture and 353 g ai ha-1 for clay soil. The selectivity index was higher than 1 for all weeds in clay soil. It was not possible to obtain the selectivity index for sandy loam soil due to species susceptibility to the herbicide.